System and method for maritime surveillance imaging and ship detection

Abstract

To provide a system for detecting a marine ship.SOLUTION: A system for detecting a marine ship comprises: a mission planning system for generating a set of tasking commands to send to a plurality of satellites in an intersatellite link (ISL) relay layer; a plurality of Earth observation satellites having overlapping accessible swaths, in which a first satellite collects first sensor data at a first set of coordinates based on a first tasking command and sends the data to the ISL relay layer, and at least a second satellite trailing behind the first satellite collects second sensor data at a second set of coordinates based on the second tasking command and the first sensor data, and sends the second sensor data to the ISL relay layer; and a reception system to receive ship detection data including the first sensor data and the second sensor data and to generate at least one vessel detection report.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The following generally relates to Earth observation and satellite imaging, and more particularly to satellite-based observation and monitoring using multiple satellites.

Background Art

[0002] Satellites provide a large amount of remotely sensed imagery that is widely used today. Satellites have several unique characteristics that make them particularly useful for remote sensing of the Earth's surface. One specific area where satellite imaging is used is Earth observation. Various problems in Earth observation, including land intelligence and change detection, asset and infrastructure monitoring, surface deformation monitoring, oil spill monitoring, humanitarian assistance and disaster relief (HADR) including flood and earthquake monitoring, agricultural monitoring, and forestry monitoring, may benefit from satellite imaging. Ship detection, including the ability to detect dark ships that do not transmit and identify illegal fishing activities, can also be achieved using satellite imagery. However, satellites generally have either a large imaging swath width or high resolution, but not both. Thus, for example, it is difficult to detect many ships within a large area of interest (AOI) and collect high-quality images of those ships in a timely manner. As the demand for satellite-based imaging increases, new systems and methods that may provide improvements over existing systems and methods are desired.

[0003] Currently, Earth Observation (EO) satellites can only receive commands or downlink data when passing over ground stations. Although the ground station network continues to grow, users must account for the satellite's "flight time" until the satellite appears within the communication cone of the ground antenna. In particular, in areas such as the middle of the ocean where there are no ground stations, there are long periods of communication outages. This can often introduce long latency in the intelligence cycle of tasking, collection, processing, exploitation, and dissemination (TCPED). Satellites using different modalities usually do not follow the same ground track and thus cannot work closely together in a coordinated manner. Additionally, the unique collection characteristics of satellites with different modalities rarely work together as a single information collection system.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Therefore, there is a need for improved satellite-based observation and monitoring systems and methods to achieve both a large imaging swath width and high resolution in applications such as maritime surveillance or ship detection, overcoming at least some of the drawbacks of existing systems and methods.

Means for Solving the Problems

[0006] Provided herein is a system for enhanced maritime vessel detection, comprising a ground segment including a mission planning system configured to receive a vessel detection command from a command device and generate a set of tasking commands based on the command, wherein each tasking command includes a set of coordinates for satellite data collection; a satellite - to - satellite link (ISL) relay layer including a plurality of relay satellites in Earth orbit, the ISL relay layer being configured to receive a set of tasking commands from the mission planning subsystem; a plurality of Earth observation satellites having overlapping accessible swaths, including a first Earth observation satellite having a first sensor and a first imaging swath width, the first Earth observation satellite being configured to receive a first tasking command including a first set of coordinates from the set of tasking commands from the ISL relay layer, collect first sensor data at the first set of coordinates, and transmit the first sensor data to the ISL relay layer; a set of trailing Earth observation satellites including at least a second Earth observation satellite, the second Earth observation satellite having a second sensor and a second imaging swath width, the second Earth observation satellite trailing the first Earth observation satellite on the same ground track as the first Earth observation satellite, the second Earth observation satellite being configured to receive a second tasking command including a second set of coordinates from the ISL relay layer, collect second sensor data at the second set of coordinates, and transmit the second sensor data to the ISL relay layer, wherein the second set of coordinates may be based on the first sensor data; and a receiving system for receiving vessel detection data including the first sensor data and the second sensor data from the ISL relay layer, the vessel detection data being processed to generate at least one vessel detection report.

[0007] The ship detection report may include at least one of the position of at least one ship, the estimated size of at least one ship, the direction of travel of at least one ship, the speed of at least one ship, the AIS data correlation of at least one ship, the image chip of at least one ship, and the classification of at least one vessel of interest (VOI).

[0008] The set of trailing Earth observation satellites may further include N Earth observation satellites that follow in sequence behind the second Earth observation satellite, where N may be any positive integer, each of the N Earth observation satellites has its own sensor and its own imaging swath width, each of the N Earth observation satellites receives its respective tasking command from the N tasking commands transmitted to the ISL relay layer by the mission planning system, collects its respective sensor data based on its respective tasking command, and may be configured to transmit its respective sensor data to the ISL relay layer.

[0009] The second tasking command may be modified based on the first sensor data.

[0010] The ISL relay layer may receive the N respective tasking commands from the mission planning system before the first sensor data is collected and transmitted to the ISL relay layer.

[0011] Each of the N respective tasking commands may be modified based on data from the Earth observation satellite that each of the N Earth observation satellites follows.

[0012] The ground segment may further include at least one command system configured to generate commands and transmit them to the mission planning system.

[0013] The ground segment may further include at least one spacecraft control system configured to control and maintain the operation of any of the plurality of Earth observation satellites.

[0014] The ground segment may further include at least one data chain subsystem configured to receive image data from at least one ground terminal and reconstruct the image data into raw data for processing into a product.

[0015] The first sensor data may be processed on a first Earth observation satellite to generate a ship detection report.

[0016] The first sensor data may be processed by at least one of a plurality of relay satellites to generate a ship detection report.

[0017] The second sensor data may be processed on a second Earth observation satellite to generate a ship detection report.

[0018] The second sensor data may be processed by at least one of a plurality of relay satellites to generate a ship detection report.

[0019] At least one of the first sensor data and the second sensor data may be transmitted to a ground terminal via a plurality of relay satellites for processing by the ground terminal of the ground segment.

[0020] The receiving system may process at least one of the first sensor data and the second sensor data to generate a ship detection report.

[0021] The receiving system may generate at least one ship detection report to be displayed on a graphical user interface of an end-user device.

[0022] The command device and the end-user device may be the same.

[0023] The second Earth observation satellite may have a smaller swath width and a higher resolution than the first Earth observation satellite.

[0024] Each of the N machine's Earth observation satellites may have a smaller swath width and a higher resolution than the previous Earth observation satellite.

[0025] A method for maritime surveillance includes receiving a command for maritime surveillance from a command device by a network interface or an input interface of a mission planning system in a ground segment; generating, by a processor of the mission planning system, a plurality of tasking commands based on the command, each tasking command including a set of coordinates for a satellite; transmitting, via an antenna system of the ground segment, the plurality of tasking commands as RF signals to an inter-satellite link (ISL) relay layer; transmitting, by an antenna system of the ISL relay layer, a first tasking command of the plurality of tasking commands to a first Earth observation satellite, the first tasking command including a first set of coordinates; collecting, by a first sensor of the first Earth observation satellite having a first remote sensing swath width, first remote sensing data at the first set of coordinates received from the ISL relay layer, and transmitting the first remote sensing data to the ISL layer via an antenna system of the first Earth observation satellite; cross-cuing at least a second Earth observation satellite to collect second remote sensing data at a second set of coordinates using a second sensor having a second remote sensing swath width via the ISL relay layer, based on the second tasking command and the first remote sensing data, the first Earth observation satellite and the second Earth observation satellite having overlapping accessible swath widths, and the second Earth observation satellite following the first Earth observation satellite on the same ground track; transmitting, via an antenna system of the second Earth observation satellite, the second remote sensing data to the ISL relay layer; transmitting, via an antenna system of the ISL relay layer, maritime surveillance information as an RF signal to a receiving system of the ground segment for display at an end-user device of the ground segment; and displaying, on a graphical user interface of the end-user device, at least one ship detection report generated from the maritime surveillance information.

[0026] The method further includes the step of cross-suing N Earth observation satellites to collect respective remote sensing data via an inter-satellite link relay layer, where N is any positive integer, each of the N Earth observation satellites follows in sequence behind a second Earth observation satellite, and the cross-suing for each of the N Earth observation satellites is based on respective tasking commands and remote sensing data from each of the Earth observation satellites that the respective N Earth observation satellites are following behind, each of the N Earth observation satellites has a Nth remote sensing swath width, and each of the N Earth observation satellites has an accessible swath width that overlaps with a first Earth observation satellite and a second Earth observation satellite.

[0027] The method may further include the step of sending a command from a command system to a mission planning system.

[0028] The method may further include at least one spacecraft control system configured to control any of the plurality of Earth observation satellites.

[0029] The method may further include at least one data chain subsystem configured to receive image data from at least one ground terminal and reconstruct the image data into raw data for processing into a product.

[0030] The method may further include the step of processing the first remote sensing data of the first Earth observation satellite to generate at least one ship detection report.

[0031] The method may further include the step of processing the first remote sensing data by at least one of the plurality of relay satellites to generate at least one ship detection report.

[0032] The method may further include the step of processing the second remote sensing data on the second Earth observation satellite to generate at least one ship detection report.

[0033] The method may further include processing the second remote sensor data by at least one of the plurality of relay satellites to generate at least one ship detection report.

[0034] The method may further include transmitting at least one of the first sensor data and the second sensor data via the ISL relay layer to a ground terminal so that it is processed by the ground terminal to generate at least one ship detection report.

[0035] The method may further include processing at least one of the first sensor data and the second sensor data by a receiving system to generate at least one ship detection report.

[0036] In the method, an end user may issue a command to the mission planning system.

[0037] In the method, the second earth observation satellite may have a smaller swath width and higher resolution than the first earth observation satellite.

[0038] In the method, each of the N earth observation satellites may have a smaller swath width and higher resolution than the previous earth observation satellite.

[0039] A method for detecting ships at sea may include the steps of tasking a wide area radio frequency (RF) collector satellite to collect RF signals from ship emitters in an area within a first set of coordinates defined by a first tasking command; collecting RF data at the first set of coordinates using the RF collector of the wide area RF collector satellite; identifying the geolocation of ship emitters in the area using the collected RF data, where the geolocation is defined by coordinates and the ship emitters are vessels of interest (VOIs); cross- cueing a C-band SAR satellite to collect C-band SAR data of the VOI using the geolocation as a second set of coordinates through an ISL relay layer including a plurality of relay satellites, where the C-band SAR satellite may have an accessible swath overlapping the wide area RF collector satellite; collecting C-band SAR data and AIS data at the second set of coordinates using the C-band SAR satellite, where the AIS data may be used to identify the VOI; cross- cueing an X-band SAR satellite to collect X-band SAR data of the VOI through the ISL relay layer, where the C-band SAR data determines a third set of coordinates and the X-band SAR satellite may have an accessible swath overlapping the wide area RF collector satellite and the C-band SAR satellite; collecting X-band SAR data at the third set of coordinates using the X-band SAR satellite; cross- cueing an optical satellite to collect optical image data of the VOI through the ISL relay layer, where the X-band SAR data determines a fourth set of coordinates and the optical satellite may have an accessible swath overlapping the wide area RF collector satellite, the C-band SAR satellite, and the X-band SAR satellite; collecting optical image data of the VOI at the fourth coordinates using the optical satellite; and downlinking maritime ship detection data including at least the optical image data to a ground segment by one of the optical satellite and the ISL relay layer.

[0040] The ship emitter may be any one of an S-band ship radar emitter, an X-band ship radar emitter, an L-band communication emitter, a UHF communication emitter, or a VHF communication emitter.

[0041] The ship detection report may be transmitted to the ground segment via the ISL relay layer for at least one of a wide-area RF collector satellite, a C-band SAR satellite, an X-band SAR satellite, and an optical satellite. The ship detection report includes at least one of the position of at least one ship, the estimated size of at least one ship, the direction of travel of at least one ship, the speed of at least one ship, the AIS data correlation of at least one ship, the image chip of at least one ship, and the classification of the ship of interest (VOI) of at least one ship.

[0042] Other aspects and features will become apparent to those skilled in the art upon review of the following description of some exemplary embodiments.

[0043] The drawings included in this specification are for the purpose of illustrating various examples of the articles, methods, and apparatuses of this specification.

Brief Description of the Drawings

[0044]

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DETAILED DESCRIPTION OF THE INVENTION

[0045] To provide examples of each claimed embodiment, various devices or processes are described below. The embodiments described below do not limit any claimed embodiment, and any claimed embodiment may be directed to a process or device different from the processes or devices described below. A claimed embodiment is not limited to an apparatus or process having all of the features of any one of the devices or processes described below, or to features common to a plurality or all of the devices described below.

[0046] One or more systems described herein may be implemented by a computer program executed on a programmable computer, each including at least one processor, a data storage system (including volatile and non-volatile memory and / or storage elements), at least one input device, and at least one output device. For example, without limitation, a programmable computer may be a programmable logic unit, a mainframe computer, a server, and a personal computer, a cloud-based program or system, a laptop, a personal digital assistant, a cellular phone, a smartphone, or a tablet device.

[0047] Preferably, each program is implemented in a high-level procedural or object-oriented programming language and / or a scripting language to communicate with the computer system. However, the program may be implemented in assembly language or machine language as needed. In any case, the language may be a compiled or interpreted language. Preferably, each such computer program configures and operates a computer when read by a storage medium or device by the computer to execute the procedures described herein, and is stored in a storage medium or device readable by a general-purpose or dedicated programmable computer.

[0048] The description of embodiments having several components communicating with each other does not imply that all such components are required. On the contrary, various optional components are described to illustrate the various possible embodiments of the present invention.

[0049] Furthermore, steps of a process, steps of a method, algorithms, etc. may be described in a sequence (in the present disclosure and / or claims), but such processes, methods, and algorithms may be configured to operate in an alternative sequence. In other words, any sequence or order of steps that may be described does not necessarily imply the requirement that the steps be executed in that order. The steps of the processes described herein may be executed in any practical order. Additionally, some steps may be executed simultaneously.

[0050] When a single device or article is described herein, it will be readily apparent that two or more devices / articles may be used instead of the single device / article (regardless of whether they cooperate). Similarly, when two or more devices or articles are described herein (regardless of whether they cooperate), it will be readily apparent that a single device / article may be used instead of the two or more devices / articles.

[0051] The following generally relates to Earth observation and satellite imaging, and more particularly to a satellite-based observation and monitoring system that uses multiple satellites and inter-satellite links (ISLs). The system may be used for any Earth observation in an area of interest (AOI), and may be particularly useful for maritime surveillance and ship detection.

[0052] The ship detection system of the present disclosure has the potential to significantly improve the ability to detect, track, and characterize vessels of interest (VOIs) at sea. The vessels may be "dark targets" that do not transmit Automatic Identification System (AIS) signals or vessels that exhibit other suspicious behavior. AIS is an automatic tracking system that uses a ship's transceiver and is used by vessel traffic services. Satellites may be used to detect AIS signatures, in which case the term satellite AIS (S-AIS) may be used. S-AIS may be used for collision avoidance, identification, and position information, as well as for applications such as maritime situation awareness, search and rescue, environmental monitoring, and maritime intelligence. Generally, the detection of dark ships involves identifying vessels that do not transmit AIS or that are spoofing AIS information, as well as hotspots where potential illegal activities are occurring.

[0053] In an embodiment, the system includes a plurality of Earth observation (EO) satellites having various remote sensing payloads including radio frequency (RF) detection, synthetic aperture radar (SAR), Automatic Identification System (AIS), and optical imaging.

[0054] As used herein, "field of regard" ("FOR") or "access" is the entire potential area perceived by a satellite's movable sensor. That is, the field of regard is the area that can be perceived within the range of movement of the movable sensor. The FOR may also be referred to as "accessible swath", and the width of the field of regard may also be referred to as "accessible swath width". "Coverage" or "field of view" (FOV) is the area perceived by the movable sensor at a particular instant and is represented by "scene". The "scene" as used herein is defined as the "imaging swath width" (the width of the area of the earth's surface perceived by the sensor) multiplied by the "along track distance". At any instant, the sensor can collect only the data of the FOV that the sensor is directed at within the FOR of that sensor.

[0055] In the ship detection system of the present disclosure, each sensor data collection satellite has an accessible swath that partially or completely overlaps with the accessible swath of any other sensor data collection satellite among the plurality of satellites, such that an accessible swath where each satellite can "image" exists on the earth, and imaging is defined as the collected data about the area (e.g., RF data, SAR data, AIS data, optical data).

[0056] A ground track or suborbital path may be defined as a path on the surface of the orbited celestial body directly below the spacecraft's orbit. That is, the ground track may be considered the vertical projection of the satellite's orbit onto the Earth's surface. Different types of satellites have different FORs with respect to the ground track. That is, some satellites have a FOR centered over the subsatellite point (i.e., "nadir-looking"), while other satellites have a "side-looking" FOR (i.e., off-nadir, switching from left-looking to right-looking or vice versa). Thus, different sensor data collection satellites within a system may not have the same ground track, but are required to have at least partially overlapping FORs (i.e., accessible swaths).

[0057] The configuration of the ISL relay layer that communicates with the leading and trailing satellites with overlapping accessible swaths enables both global (or near-global depending on the type of Earth orbit) near-real-time (NRT) tasking and global NRT downlink of information. The ISL relay layer includes a plurality of satellites that transmit information to and receive information from the imaging satellites. The inter-satellite link relay layer with a plurality of satellites may sometimes be referred to as an ISL relay constellation.

[0058] A "trailing satellite" is a satellite that passes through the area of interest (AOI) after a "leading satellite". "Trailing time" or "trailing interval" is the amount of time between the leading satellite passing through the location of interest and the trailing satellite passing through the location of interest. The trailing time may be on the order of minutes, preferably on the order of minutes.

[0059] Performing a cross-queuing operation using the ISL relay layer enables a short latency between spacecraft in a ship detection system. "Cross-queuing" is the passing of detection, geolocation, and aiming information to another sensor with minimal or no human intervention. Relaying commands and data through the ISL relay layer enables rapid and efficient cross-queuing between a leading satellite and a trailing satellite, which enables the short latency of the ship detection system. The overlapping area of the accessible swaths of the satellites is the cross-queuable overlapping area, in which the leading satellite can cross-queue to the trailing satellite to further image within the area.

[0060] The system utilizes the unique characteristics of each satellite, including the imaging swath width, image resolution, and / or position of the FOV of each satellite (i.e., the satellite swath size and resolution of the trailing satellite may be the same as the leading satellite, but the FOV may be directed in a different direction), and connects those satellites via an inter-satellite link (ISL) data relay layer to enable automatic or semi-automatic cross-queuing between satellites with overlapping accessible swaths. Cross-queuing is the process by which the first satellite sends a request to the second satellite to be "queued up" to observe the same target later as the first satellite.

[0061] Generally, the ship detection system of the present disclosure uses a plurality of imaging satellites with overlapping accessible swaths having different accessible swath widths and thus different imaging resolutions to identify vessels of interest (VOIs) within an area of interest (AOI). However, within the system, satellites having the same sensor type, swath width, and resolution may be used to "image" different fields of view (FOVs) at different times. That is, data collected by a preceding satellite may, depending on the situation, necessitate that similar image sizes and qualities be subsequently collected by a following satellite, but at different or overlapping positions. For example, both the preceding and following satellites may be RF sensor satellites having the same accessible swath width and resolution, but the following RF sensor satellite may be tasked to collect data at a different location than the preceding RF sensor satellite. Using multiple satellites of different modalities with overlapping accessible swaths, all communicating with an inter-satellite link (ISL) relay layer, enables improved revisit times, improved tasking and downlink latency by avoiding flight times to ground stations, and the ability to cross cue between multiple satellites based on information received from previous satellites.

[0062] As an example, in one embodiment, an imaging satellite constellation includes a first imaging satellite, a second imaging satellite, and a third imaging satellite, and the first, second, and third satellites have overlapping accessible swaths. The first imaging satellite collects sensor data having a first imaging swath width and a first resolution, which may vary depending on the sensor type. For example, an RF collector satellite has no resolution. The second imaging satellite collects sensor data having a second imaging swath width and a second resolution, where the second imaging swath width is smaller than the first imaging swath width, and the second resolution is higher than the first resolution if the first resolution exists. The third imaging satellite collects sensor data having a third imaging swath width and a third resolution, where the third imaging swath width is smaller than the second imaging swath width, and the third resolution is higher than the second resolution. In certain embodiments, the three satellites include a wide-area C-band SAR satellite, a high-resolution X-band SAR satellite, and a high-resolution electro-optical satellite.

[0063] As described above, generally, the imaging swath width and the resolution are inversely correlated. That is, in most situations, in order to have a higher resolution, the satellite must have a smaller imaging swath width. Generally, the "earlier" satellites in a series of satellites that collect data have a larger imaging swath width so that a VOI (or other feature of interest) can be detected, while the "later" satellites in the series of satellites have a higher resolution to better identify or characterize the detected VOI. However, depending on the situation, there may be cases where a later satellite needs to have an imaging swath width and resolution similar to those of the previous leading satellite. Any satellite can be a later satellite as long as the satellites have overlapping accessible swaths.

[0064] As discussed above, it is not a requirement of the system for each trailing satellite to have a different sensor type, a different imaging swath width, or a different resolution compared to the leading satellite. However, every satellite must have overlapping accessible swaths. The trailing satellite may, in some embodiments, be exactly the same type of satellite as the leading satellite (or collect the same type of sensor data), or the third satellite may be the same as the first satellite.

[0065] In another embodiment, further described below, four imaging satellites are used for ship detection. Each of the four imaging satellites uses a different modality or sensor type for data collection. Detection of the VOI is performed using a cross-queuing process from the imaging satellite with the largest imaging swath (and lowest resolution, if applicable) to the satellite with the smallest imaging swath / highest resolution. The first imaging satellite may be a radio frequency (RF) satellite with an ISL for wide area RF collection and communication with the ISL relay layer. The first imaging satellite may have a very wide imaging swath area, for example, exceeding 1000 km. When the first imaging satellite is an RF satellite, there is no resolution (since RF data does not have resolution per se, but rather provides geolocation of RF emitters on Earth). The second imaging satellite may be a synthetic aperture radar (SAR) satellite with an SAR collector, an automatic identification system (AIS) for ships, and an ISL for communication with the ISL relay layer. The second imaging satellite, if applicable, has a wide imaging swath width smaller than that of the first satellite, for example, an imaging swath width exceeding 450 km, with a low to medium imaging resolution, for example, from 25 m to 50 m, higher than that of the first imaging satellite. The third imaging satellite may be an X-band SAR satellite with a high-resolution X-band SAR collector and an ISL for communication with the ISL relay layer. The third imaging satellite has a medium to small imaging swath width, for example, an imaging swath width exceeding 30 km, smaller than that of the second imaging satellite, with a high to ultra-high imaging resolution, for example, from 0.25 m to 3 m, higher than that of the second imaging satellite. The fourth imaging satellite may be an optical satellite with a high-resolution optical collector and an ISL for communication with the ISL relay layer. The fourth imaging satellite has a small imaging swath width, for example, an imaging swath width exceeding 5 km, smaller than that of the third satellite, with an ultra-high imaging resolution, for example, 0.5 m, higher than that of the third imaging satellite.

[0066] In the present disclosure, all imaging satellites that perform imaging operations before a subsequent imaging satellite may be considered as "preceding satellites" with respect to the subsequent imaging satellite, and the subsequent satellite may be considered as a "following satellite" with respect to the previous satellite. That is, in an embodiment having four imaging satellites, the first imaging satellite may be considered as a "preceding satellite", and the second to fourth imaging satellites may be considered as "following" satellites of the first imaging satellite. The second imaging satellite may be considered as a "preceding satellite" with respect to the third and fourth imaging satellites, and the third and fourth imaging satellites may be considered as "following" satellites with respect to the second imaging satellite, and so on. When used in connection with satellites in this specification, the terms "preceding" and "following" are not intended to indicate any particular physical relationship between the preceding satellite and the following satellite. Rather, they refer to the fact that the following satellite is used to perform an imaging operation (i.e., data acquisition) based on the imaging operation performed by the preceding satellite after the imaging operation performed by the preceding satellite.

[0067] As used herein, "imaging", "imaging satellite", "imaging operation", etc. are meant to refer to the collection of data regarding an area of interest (AOI) by a satellite sensor, and are not particularly intended to refer to the creation of an image. For example, in the case of an RF sensor satellite, the imaging operation is the collection of RF data by the RF sensor satellite regarding the AOI to detect an RF radiation source and identify its geographical location.

[0068] In some cases, the trailing satellite may be considered to physically follow the leading satellite with a time period difference (e.g., 10 minutes). This time period may be referred to as the "trailing interval" or "trailing time". The trailing interval defines the time period from when the leading satellite passes over a location (i.e., the location is within the satellite's FOR) until the trailing satellite passes over the same location (i.e., thus, the same location or substantially the same location can be imaged by both satellites). In such cases, the leading satellite first acquires image data at a location, and the trailing satellite then acquires image data at substantially the same location (depending on whether the subject being imaged is stationary or moving, or whether the subject was fully captured in the previous image). As a result, the system is generally configured to perform certain processing and communication steps, such as the processing and communication steps performed by the inter-satellite link relay layer described herein, within the trailing interval.

[0069] Each imaging satellite receives tasking commands through the ISL relay layer (i.e., indirectly from the command system or the previous satellite) and sends back relevant data to the ISL relay layer. The tasking commands for the trailing satellite are modified based on the data collected by the previous (leading) satellite. For example, the tasking commands sent to the second imaging satellite are determined at least in part based on the data collected by the first imaging satellite via the ISL relay layer.

[0070] In an embodiment, the first command for ship detection may be received from an end user who is either in-theatre or not in-theatre. The command is received in the ISL relay layer and transmitted to the mission planning system of the associated ground segment. The ground segment may also include a command system, a spacecraft control system, and a data chain system. The ground segment may be cloud-based. The mission planning system creates a tasking command based on the command and transmits the tasking command to the ISL relay layer for transmission to the first imaging satellite. When each imaging satellite transmits the data it has collected to the ISL relay layer, the ISL relay layer downlinks the relevant data to the end user. The end user may be the same as the original end user or different, and may be in-theatre or not in-theatre.

[0071] In some embodiments, there may be more than five or less than three imaging satellites used within the detection system, and one or more of the imaging satellites within the detection system may not be employed for a particular ship detection command. Thus, in some embodiments, the system includes a constellation of imaging satellites and may use only a subset of the imaging satellites available for the execution of a given task. The first command may include tasks for multiple satellites or may task only the first satellite, and the second satellite is tasked based on the information collected from the first satellite.

[0072] The ship detection system may utilize recent developments in inter-satellite link technology, primary optical inter-satellite link (OISL) terminals, and the emergence of OISL-compatible data relay communication constellations. Generally, existing systems cannot task from the field, process (on-board), cross-cue to another asset, and downlink intelligence products to users at the same (or different) field, particularly not in any low-latency or automated way. The systems of the present disclosure may provide reduced latency in post-pass time and cross-cue tasking. Since the time during which the VOI moves while the image is being acquired is reduced, the probability of imaging and characterizing a particular VOI is higher when the latency in post-pass time between satellites and cross-cue tasking is very short. Further, when the latency in cross-cue is short, surveillance of faster moving VOIs can be maintained.

[0073] Referring now to FIG. 1A, shown therein is a block diagram of a ship detection system 100 according to an embodiment, including satellites of a plurality of different modalities (i.e., different sensor types) having overlapping accessible swaths for ship detection of a ship of interest within a region of interest. FIG. 1A shows a simplified version of the overall process, while variations of specific steps are shown and considered in FIGS. 1B-1D.

[0074] System 100 includes a command system 102, a mission planning system 104, a receiving system 106, an inter-satellite link relay layer (ISL relay layer) 110, a first imaging satellite 120, a second imaging satellite 130, a third imaging satellite 140, and a fourth imaging satellite 150. Although FIGS. 1A and system 100 include only four satellites (with different sensor types, imaging swath widths, and resolutions where applicable, as described below), it should be understood that the number of imaging satellites available for tasking in system 100 may likely be more than four. Further, a subset of the imaging satellites available for tasking may have the same sensor type, imaging swath width, and resolution where applicable, but may be in different locations along a ground track, for example, where an optical sensor satellite is following another optical satellite.

[0075] The ISL relay layer 110 includes a plurality of satellites in Earth orbit. The satellites of the ISL relay layer 110 may be in low Earth orbit (LEO), medium Earth orbit (MEO), or geostationary orbit (GEO). The ISL relay layer may include, for example, up to hundreds or thousands of satellites. In some embodiments, all of the relay satellites may be on the same orbit (e.g., all satellites are on GEO). In some embodiments, relay satellites may exist on different orbits (e.g., satellites on LEO and satellites on MEO exist). In some embodiments, the same satellite may be used for more than one step, or multiple satellites may be used for a single step. For example, when a command is received by a relay satellite of the ISL relay layer, the command may "hop" between several different satellites within the ISL relay layer before being transmitted to the mission planning system 104.

[0076] The first imaging satellite 120 includes a collector 122 of a first sensor type and an ISL 124.

[0077] The second imaging satellite 130 includes a collector 132 of a second sensor type and an ISL 134.

[0078] The third imaging satellite 140 includes a collector 142 of a third sensor type and an ISL 144.

[0079] The fourth imaging satellite 150 includes a collector 152 of a fourth sensor type and an ISL 154.

[0080] In an embodiment, the collector 122 of the first sensor type is an RF sensor that collects RF geolocation data, and the imaging swath width of the collector 122 of the first sensor type is larger than the imaging swath width of the collector 132 of the second sensor type. The RF satellite provides position information of RF emitters from ships. The data collected by the collector 122 of the first sensor type is used to notify data collection by the collector 132 of the second sensor type. Depending on the situation, since dark ships may not broadcast RF emitters, the data collected from the collector of the first sensor type (when it is an RF sensor) may not notify data collection by the collector 132 of the second sensor type.

[0081] The resolution of the collector 132 of the second sensor type is lower than that of the collector 142 of the third sensor type, and the imaging swath width of the collector 132 of the second sensor type is larger than that of the collector 142 of the third sensor type. In some embodiments, the resolution of the collector 142 of the third sensor type is lower than that of the collector 152 of the fourth sensor type, and the imaging swath width of the collector 142 of the third sensor type is larger than that of the collector 152 of the fourth sensor type. However, in other embodiments, the resolution of the collector 152 of the fourth sensor type may be less than or equal to that of the collector 142 of the third sensor type, but instead may provide details of color or other images that were not collected or could not be collected by the collector 142 of the third sensor type. For example, in some embodiments, the collector 142 of the third sensor type may have a resolution of 3m, and the collector of the fourth sensor type may have a resolution of 0.5m, while in other embodiments, the collector 142 of the third sensor type may have a resolution of 0.25m, and the collector 142 of the fourth sensor type may have a resolution of 0.5m.

[0082] In the embodiment of FIG. 1A, each of the four satellites uses a different imaging modality and / or a different sensor type (e.g., different imaging frequencies) to collect data, but in other embodiments, the same imaging modality or sensor type may be used by at least two of the tasked imaging satellites.

[0083] In other embodiments, there may be fewer than three or more than five imaging satellites.

[0084] Generally, an imaging satellite with a larger imaging swath width performs data collection before a subsequent imaging satellite with a smaller imaging swath width. Depending on the situation, for example, when the FOV of the AOI needs to be adjusted within the FOR based on already collected data, the trailing satellite may have the same imaging swath width as the immediately preceding leading satellite.

[0085] Generally, the imaging swath width and resolution used may be selected from those particularly suitable for maritime surveillance applications.

[0086] During operation of the system 100 of FIG. 1A, commands are created by the command system 102, and the command system 102 transmits the commands to the ISL relay layer 110, i.e., to the satellites within the ISL relay layer 110. The commands may be generated based on input data provided by the user via a user interface.

[0087] The command system 102 enables the user to describe requirements regarding the acquisition and downlink of data from the ship detection system 100 and / or the generation of one or more products via the creation and submission of commands at the human machine interface (HMI). In some embodiments, the command system 102 may also be a system that distributes data or products to clients.

[0088] The ISL relay layer 110 transmits the commands to the mission planning system 104. The mission planning system 104 processes the received commands and generates one or more tasking commands. The tasking commands are transmitted by the mission planning system 104 to the ISL relay layer 110, i.e., to the satellites within the ISL relay layer 110, which may or may not be the same satellite that receives the commands from the command system 102.

[0089] In other embodiments, the command system 102 may send commands directly to the mission planning system 104 (arrow between the command system 102 and the mission planning system 104).

[0090] The mission planning system 104 may plan all activities of the satellites within the ISL relay layer 110. These activities may include image acquisition, data downlink or relay, and / or spacecraft (e.g., satellite) maintenance activities. Requests for maintenance activities are sent from a spacecraft control system (not shown) to the mission planning system 104.

[0091] The spacecraft control system is responsible for maintaining the functions and safe operation of the satellites in the ISL relay layer 110, executing the satellite activities provided by the mission planning system, providing orbit determination, prediction, and maintenance functions, and providing offline analysis to support long-term monitoring of the satellite operations.

[0092] The ISL relay layer 110 sends a tasking command to the first imaging satellite 120, and a collector 122 of the first sensor type collects sensor data based on the received tasking data.

[0093] In some embodiments, the first imaging satellite 120 transmits the collected sensor data to the ISL relay layer 110 via the ISL 124 to be relayed to the ground terminal 108 for processing, and the processed collected sensor data is returned to the ISL relay layer 110. In some embodiments, the collected sensor data is processed by the first imaging satellite 120. The ISL relay layer 110 relays the tasking command and, depending on the situation, the processed collected sensor data to the second imaging satellite 130. The ISL relay layer 110 transmits the tasking command (which may or may not have been modified based on the data collected and transmitted by the first imaging satellite 120) and, optionally, the collected sensor data to the second imaging satellite 130 for subsequent imaging operations.

[0094] The second imaging satellite 130 receives a tasking command from the ISL relay layer 110 and uses a collector 132 of a second sensor type to collect sensor data based on the tasking command. The second imaging satellite 130 transmits the collected sensor data to the ISL relay layer 110 via the ISL 134.

[0095] In some embodiments, the second imaging satellite 130 transmits the collected sensor data to the ISL relay layer 110 via the ISL 134 so as to be relayed to the ground terminal 108 for processing, and the processed collected sensor data is returned to the ISL relay layer 110. In some embodiments, the collected sensor data is processed by the second imaging satellite 130. In all embodiments, the ISL relay layer 110 relays the tasking command and, depending on the situation, the processed collected sensor data to the third imaging satellite 140.

[0096] The ISL relay layer 110 transmits the tasking command (which may or may not have been modified based on the data collected by the first and second imaging satellites) and, optionally, the collected sensor data to the third imaging satellite 140 for subsequent imaging operations.

[0097] The third imaging satellite 140 uses a collector 142 of a third sensor type to collect sensor data based on the tasking command. The third imaging satellite 140 transmits the collected sensor data to the ISL relay layer 110 via the ISL 144.

[0098] The ISL relay layer 110 transmits the tasking command (which may or may not have been modified based on the data collected by the first, second, and third imaging satellites) and, optionally, the collected sensor data to the fourth imaging satellite 150.

[0099] The fourth imaging satellite 150 uses a collector 152 of the fourth sensor type to collect sensor data based on a tasking command. The fourth imaging satellite 150 transmits the collected sensor data to the ISL relay layer 110 via the ISL 154.

[0100] In some embodiments, the third imaging satellite 140 transmits the collected sensor data to the ISL relay layer 110 via the ISL 144 so as to be relayed to the ground terminal 108 for processing, and the processed collected sensor data is returned to the ISL relay layer 110. In some embodiments, the collected sensor data is processed by the third imaging satellite 140. The ISL relay layer 110 relays the tasking command and, depending on the situation, the processed collected sensor data to the fourth imaging satellite 150.

[0101] The ISL relay layer 110 transmits data to the receiving system 106. The receiving system 106 is configured to output the received data, such as via a display device that displays a graphical user interface. In the embodiment of FIG. 1A, the data is transmitted to the receiving system after all the data has been collected by the ISL relay layer 110. In a preferred embodiment, the data is transmitted from the ISL relay layer 110 to the receiving system as soon as the data is collected by the imaging satellite, particularly when the collected data includes the VOI (see FIG. 1D).

[0102] When data is transmitted from each imaging satellite to the corresponding relay satellite and then from the relay satellite to the next imaging satellite, this represents a cross-queuing operation. Cross-queuing involves passing detection, geolocation, and aiming information directly to another sensor. Generally, each subsequent data collection at an imaging satellite represents an imaging swath that gradually narrows, enabling the ship detection system to narrow down a specific VOI and gain a deeper understanding of the characteristics and behavior of the ship.

[0103] Figures 1B - 1D show different implementations of the various steps described above with respect to Figure 1A according to an embodiment. The system 100 of Figures 1B - 1D is the same as the system 100 of Figure 1A. The ISL relay layer 110 represents a plurality of satellites. As considered above, multiple satellites within the ISL relay layer 110 may be used for a single task, or a single satellite may be used for multiple tasks. Figures 1B - 1D do not illustrate specific satellites to show this point.

[0104] Figure 1B shows a variation of the command and pre - planning steps during the operation of the ship detection system 100. In Figure 1B, tasking commands (dashed arrows) are sent directly from the mission planning system 104 to the ISL relay layer 110 for each of the imaging satellites 120, 130, 140, 150. The ISL relay layer 110 sends the tasking commands to the imaging satellites 120, 130, 140, and 150 (solid arrows). That is, the mission planning system 104 can task any imaging satellite for collection at any time, and thus there is no need for the transfer of tasking commands from a preceding satellite to a succeeding satellite. The mission planning system 104 may task each satellite to "look" in a specific direction within the FOR of the satellite, and during a collection event, the final imaging coordinates corresponding to the location of the VOI determined by a preceding satellite, if any, are sent through the ISL relay layer 110 to the appropriate succeeding satellite by the preceding satellite.

[0105] Figure 1C shows the transmission of the coordinates of the VOI between imaging satellites during the operation of the ship detection system 100. As considered above with respect to Figure 1B, the imaging coordinates corresponding to the VOI are sent from each satellite to the succeeding satellite through the ISL relay layer 110. In Figure 1C, the coordinates of the VOI are sent through the ISL relay layer 110 from satellite 120 to satellite 130, from satellite 130 to satellite 140, and from satellite 140 to satellite 150. That is, when a preceding satellite sensor processes data / images on - board, the coordinates of the VOI for the succeeding sensor to image are calculated and those coordinates are sent through the ISL relay layer 110.

[0106] Figure 1D shows the transmission of data to the receiving system 106 during the operation of the ship detection system 100. As discussed above, data such as images, detection of VOIs, and coordinates are preferably transmitted to the receiving system 106 as soon as the data becomes available. In Figure 1D, the data collected from satellites 120, 130, 140, and 150 is transmitted to the ISL relay layer 110 and then directly to the receiving system 106.

[0107] Referring now to Figure 2, shown therein is a flowchart of a method 200 for detecting an interested ship by satellite imaging using the system 100 of Figures 1A - 1D according to an embodiment.

[0108] At 202, a command is generated in the command system 102 and transmitted from the command system 102 to the satellites of the ISL relay layer 110. The command system 102 may be on - site (e.g., on a ship at sea) or off - site (e.g., not at sea).

[0109] In some embodiments, the command may be transmitted directly to the mission planning system (see 204 below). For example, a ship at sea is likely to need to transmit commands through the ISL relay layer 110, while commands issued from a facility that can access an online command desk go directly to the mission planning system.

[0110] Instructions may specify an area of interest (the "AOI") where data collection is to occur. The AOI may be a defined area polygon or individual collection swaths. Instructions may specify a date range or time range. Instructions may specify a priority for the instruction. For example, where there are multiple instructions pending, the priority of the instruction may specify which takes precedence. With respect to the SAR sensor, the instructions may specify one or more desired beam modes. Instructions may specify one or more sensor types or modalities for which data is to be collected and received. Sensor types that may be specified by the instructions may include, for example, without limitation, RF sensing, C-band SAR sensing, AIS, X-band SAR, optics, etc. Instructions may specify at least one destination. The destination specifies the device to which the collected or processed data is to be sent. The instruction system 102 may be configured to generate and display a user interface by which a user may select various instruction parameters to define the content of the instruction. The instruction system 102 may enable a user to select various parameters based on certain provided criteria, such as selecting an AOI based on a date range ("swath-based instruction").

[0111] In 204, the ISL relay layer transmits an instruction to the mission planning system 104.

[0112] In some embodiments, the mission planning system 104 may receive the instruction directly from the instruction system 102.

[0113] The ISL relay layer 110 provides continuous connectivity between the instruction system 102 and the mission planning system 104. Thus, instructions may be issued from any end-user location on Earth.

[0114] The command may be received at the receiving station and then transmitted to a cloud-based mission planning system that is part of the ground segment associated with the ship detection system 100. The command may be received at the downlink receiving station antenna of the cloud-based ground segment. The ground segment may also include a command system, a spacecraft control system, and a data chain system. The command system, the spacecraft control system, and the data chain system may be in different locations and may be cloud-based.

[0115] As discussed above, the command system may include a human-machine interface for the user to input requirements regarding data acquisition and downlink or product generation in order to create commands and submit them to the mission planning system 104.

[0116] As discussed above, the spacecraft control system may be responsible for maintaining the functions and safe operation of the satellites in the ISL relay layer 110, executing the satellite activities provided by the mission planning system, providing orbit determination, prediction, and maintenance functions, and providing offline analysis to support long-term monitoring of the satellite operations. The spacecraft control system may send maintenance requests to the mission planning system 104.

[0117] The data chain subsystem may be responsible for receiving image data from at least one ground terminal and reconstructing the image data into raw data to be processed into products such as image products, information products, and non-imaging calibration products.

[0118] The command received in the mission planning system 104 may be generated in and identical to the command sent by the command system 102.

[0119] In 206, the mission planning system 104 checks the availability of satellites of each sensor type within the system and plans data collection and spacecraft tasking commands. The type and number of tasking commands depend on the content of the command and the number of sensors (different imaging satellites) required by the command. Although four imaging satellites were described in the embodiment of FIG. 1, only two different imaging satellites, and three or five or more different imaging satellites may be employed as needed.

[0120] The mission planning system 104 transmits tasking commands to the ISL relay layer 110.

[0121] In 208, the ISL relay layer 110 transmits tasking commands to the first imaging satellite 120 via the ISL link 124. The first imaging satellite 120 has a collector 122 of a first sensor type for collecting first sensor data. The collector 122 of the first sensor type has a wide imaging swath.

[0122] In 210, the collector 122 of the first sensor type of the first imaging satellite 120 collects first sensor data defined by the tasking command. The collected first sensor data may be geolocation data of the AOI specified by the command. The geolocation data may be collected from a marine emitter. The marine emitter may be any one of an S-band marine radar emitter, an X-band marine radar emitter, an L-band communication emitter, a UHF communication emitter, or a VHF communication emitter. In some embodiments, a part of the emitter may be classified as an emitter of interest (EOI) imaged by the sensors of satellites of other sensor types of the ship detection system.

[0123] The imaging swath width of the first imaging satellite 120 is the widest imaging swath of the imaging satellite and may be greater than 1000 km.

[0124] The first imaging satellite 120 transmits the collected data to the ISL relay layer 110 via the ISL 124.

[0125] At 212, the ISL relay layer 110 transmits the tasking command and, optionally, the sensor data collected by the first imaging satellite 120 to the second imaging satellite 130 via the ISL link 134.

[0126] The tasking command may be modified from the original tasking command created by the mission planning system 104 based on the data collected by the first imaging satellite. That is, after the first imaging satellite 120 collects image data, the image data is processed on board the first imaging satellite 120 for ship detection, and the tasking command for the second imaging satellite 130 is modified to include the coordinates of the detected VOI. As discussed above, the second imaging satellite 130 may have already received directly from the mission planning system 104 a tasking command that is directed towards the overall orientation of the AOI within the FOR of the second imaging satellite 130. At that time, the modified tasking command may adjust the specific FOV of the second imaging satellite 130.

[0127] In some embodiments, the sensor data collected by the first imaging satellite 120 is transmitted from the ISL relay layer 110 to the end user as soon as possible.

[0128] At 214, the collector 132 of the second sensor type of the second imaging satellite 130 collects the data required by the tasking command. The required data may be a C-band SAR image of the VOI within the AOI. The required data may be Automatic Identification System (AIS) data. The imaging swath width of the second imaging satellite 130 is smaller than the imaging swath of the first imaging satellite and may be greater than 500 km. If applicable, i.e., if the first imaging satellite has a resolution, the resolution of the second imaging satellite 130 is higher than that of the first imaging satellite.

[0129] The second imaging satellite 130 transmits the collected data to the ISL relay layer 110 via the ISL 134.

[0130] At 216, the ISL relay layer 110 transmits a tasking command and, optionally, sensor data collected by the second imaging satellite 130 to the third imaging satellite 140 via the ISL link 144. The tasking command may be modified from the original tasking command created by the mission planning system 104 based on data collected by the first and / or second imaging satellites 120, 130.

[0131] In some embodiments, the sensor data collected by the second imaging satellite 130 is transmitted from the ISL relay layer 110 to the end user as soon as possible.

[0132] At 218, the collector 142 of the third sensor type of the third imaging satellite 140 collects the data required by the tasking command. The required data may be high-resolution X-band SAR data. The imaging swath width of the third imaging satellite 140 is smaller than that of the second imaging satellite and may be greater than 30 km. The resolution of the third imaging satellite 140 is higher than that of the second imaging satellite.

[0133] The third imaging satellite 140 transmits the collected data to the ISL relay layer 110 via the ISL 144.

[0134] At 220, the ISL relay layer 110 transmits a tasking command and, optionally, sensor data collected by the third imaging satellite 140 to the fourth imaging satellite 150 via the ISL link 154.

[0135] The tasking command may be modified from the original tasking command created by the mission planning system 104 based on data collected by the first, second, and / or third imaging satellites.

[0136] In some embodiments, the sensor data collected by the third imaging satellite 140 is transmitted from the ISL relay layer 110 to the end user as soon as possible.

[0137] In 222, the collector 152 of the fourth sensor type of the fourth imaging satellite 150 collects the data required by the tasking command. The required data may be high-resolution optical images of at least one VOI collected by a high-resolution optical collector. The imaging swath width of the fourth imaging satellite 150 is smaller than the imaging swath of the third imaging satellite and may be greater than 5 km. The resolution of the fourth imaging satellite 150 is higher than that of the third imaging satellite.

[0138] The fourth imaging satellite 150 transmits the collected data to the ISL relay layer 110 via the ISL 154.

[0139] In 224, the ISL relay layer 110 transmits the information collected from all four imaging satellites to the end user device relevant to the end user. The end user device may be on-site or not on-site. In other embodiments, as described above, the information collected by each imaging satellite is transmitted to the end user as soon as the information becomes available.

[0140] As discussed above, the trailing satellite does not always have a smaller imaging swath and higher resolution than the leading satellite, and the above embodiments are merely examples.

[0141] Next, referring to FIG. 3, shown therein is a block diagram of a ship detection system 300 according to an embodiment. The system 300 may be an embodiment of the system 100 of FIG. 1.

[0142] System 300 includes an end-user command system 302, a mission planning system 304, an end-user receiving system 306, an inter-satellite link relay constellation (ISL relay constellation) 310, an RF satellite 320, a wide-area C-band SAR satellite 330, a high-resolution X-band SAR satellite 340, and an optical satellite 350.

[0143] The ISL relay constellation 310 is in Earth orbit. The ISL relay constellation 310 may be in low Earth orbit (LEO), medium Earth orbit (MEO), or geostationary orbit (GEO). The ISL relay constellation 310 includes a plurality of relay satellites, and a subset of those relay satellites is shown as satellites 311, 312, 313, 314, 315, and 316 in FIG. 3. In practice, the number of relay satellites in the ISL relay constellation 310 may be hundreds or more. A single relay satellite may be used for multiple steps in ship detection, or multiple relay satellites may be used for a single step in ship detection. For example, when a command generated in the end-user command system 302 is received by a relay satellite of the ISL relay constellation 310, the command may "hop" between several different satellites within the ISL relay constellation 310 before being transmitted to the mission planning system 304.

[0144] The RF satellite 320 includes a wide-area RF collector 322 for collecting RF data and an ISL 324.

[0145] The wide-area SAR satellite 330 includes a wide-area C-band SAR and AIS collector 332 for collecting C-band SAR data and an ISL 334.

[0146] The next-generation X-band SAR satellite 340 includes a high-resolution X-band SAR collector 342 for collecting X-band SAR data and an ISL 344.

[0147] Optical satellite 350 includes a high-resolution optical collector 352 for collecting high-resolution optical images and an ISL 354.

[0148] The imaging swath width of RF satellite 320 is larger than that of wide-area SAR satellite 330.

[0149] The resolution of wide-area SAR satellite 330 is lower than that of next-generation X-band SAR satellite 340, and the imaging swath width of wide-area SAR satellite 330 is larger than that of next-generation X-band SAR satellite 340.

[0150] The resolution of next-generation X-band SAR satellite 340 is lower than that of optical satellite 350, and the imaging swath width of next-generation X-band SAR satellite 340 is larger than that of optical satellite 350.

[0151] In other embodiments, there may be less than 3 imaging satellites or 5 or more imaging satellites.

[0152] Broadly speaking, during the operation of system 300, a command is created by operating system 302 in response to the reception of a user input and is transmitted to ISL relay satellite 311. Relay satellite 311 transmits the command to mission planning system 304, and the command is used to create a tasking command for the imaging satellites. The tasking commands are directly transmitted to imaging satellites 320, 330, 340, and 350 through relay satellites 312, 313, 314, and 315 respectively to initially task the imaging satellites. The initial tasking commands the imaging satellites 320, 330, 340, and 350 to face the same overall direction and may include precise coordinates for imaging. Relay satellite 312 transmits the tasking command to RF satellite 320, and wide area RF collector 322 collects the required data and transmits the data to relay satellite 313 via ISL 324. Relay satellite 313 transmits the tasking command to wide area SAR satellite 330 (the tasking commands may have been modified based on the data collected and transmitted by RF satellite 320 or may not have been modified, for example, the modification changes the imaging coordinates of the initial tasking). Wide area C-band SAR and AIS collector 332 collects the required data and the data is transmitted to relay satellite 314 via ISL 334. Relay satellite 314 transmits the tasking command to next generation X-band SAR satellite 340 (the tasking commands may have been modified based on the data collected by the first satellite and Class C-V SAR satellite or may not have been modified). High resolution X-band SAR collector 342 collects the required data and the data is transmitted to relay satellite 315 via ISL 344. Relay satellite 315 transmits the tasking command to optical satellite 350 (the tasking commands may have been modified based on the data collected by the first satellite, the second satellite, and the next generation X-band SAR satellite or may not have been modified). High resolution optical collector 352 collects the required data and the data is transmitted to relay satellite 316 via ISL 354.Relay satellite 316 transmits data to receiving system 306 so as to be received by an end user.

[0153] When data is transmitted from each preceding imaging satellite to the associated relay satellite and then to the succeeding satellite, this represents a cross-queuing operation. Cross-queuing involves directly passing detection, geolocation, and aiming information to another sensor. Generally, although not always, as data collection by the ship detection operation progresses, the imaging swath width becomes narrower, enabling the ship detection system to narrow down to a specific VOI.

[0154] Referring now to FIG. 4, shown therein is a flowchart of a method 400 for ship detection using the system 300 of FIG. 3, according to an embodiment.

[0155] At 402, a command is generated in command system 302 in response to an end user input specifying details of the command. The command is transmitted by command system 302 to a first relay satellite 311 of the ISL relay constellation 310.

[0156] The end user may be on-site, for example, on board a Five Eyes (FVEY) ship, and the ship may be requesting information regarding a VOI within an area of interest that it will soon be heading into perilously. The command system 302 may be implemented at an information agency on land where the user is not on-site, for example, where the user may use the command system 302 to request information about the VOI.

[0157] The instructions may contain various information. (For example, it may be selected to be specified by the user through input to the user interface) The information within the instructions may include, for example, the area of interest (AOI) where data collection is to be performed (such as a defined area polygon or individual collection swaths). The instructions may include a date range (or time range). The instructions may include the priority of the instructions (for example, which one takes precedence when there are multiple instructions on hold). The instructions may include one or more desired modes. The instructions may specify from which sensor type to receive data (for example, RF sensing, C-band SAR sensing, AIS, X-band SAR, optical, etc.). The instructions may include at least one destination to which the collected data is to be sent. The instruction system 302 may enable the user to select various parameters based on specific provided criteria (such as selecting an AOI based on a date range) ("swath-based instructions").

[0158] In 404, the relay satellite 311 transmits instructions to the mission planning system 304.

[0159] The ISL relay constellation 310 provides continuous connectivity between the instruction system 302 and the mission planning system 304. Thus, the instructions can be issued from any location of the end-user on Earth. The instructions are received at the receiving station and then may be transmitted to a cloud-based mission planning system that is part of the ground segment associated with the ship detection system 300. The instructions may be received at the downlink receiving station antenna of the cloud-based ground segment. The antenna may be known in advance based on the instruction information or the end-user.

[0160] The instructions received in the mission planning system 304 may be the same as the instructions generated in the instruction system 302 and transmitted by the instruction system 102.

[0161] At 406, the mission planning system checks the availability of satellites of each sensor type within the system and plans data collection and satellite tasking commands. In the embodiments of FIGS. 3 and 4, the available satellite sensor types are RF, C-band SAR, X-band SAR, and high-resolution optics. In the systems and methods of the present disclosure, the type and number of tasking commands depend on the nature of the commands, as well as the number of sensors (different imaging satellites) required and / or available.

[0162] The mission planning system 304 transmits tasking commands to the relay satellite 312. Since the ship detection system 300 employs an ISL constellation on LEO, MEO, or GEO, near real-time (NRT) tasking of the satellites can be achieved. The first tasking command is for the RF satellite 320.

[0163] At 408, the relay satellite 312 transmits tasking commands to the RF satellite 320 via the ISL link 324. In some embodiments, the RF satellite may be a single satellite, while in other embodiments, a cluster of RF satellites may be used.

[0164] At 410, the wide-area RF collector 322 of the RF satellite 320 collects data based on the tasking commands. The RF collector 322 collects RF data from the AOI. The RF data may be processed on board the RF satellite 320 or transmitted to the ground via the ISL constellation 310 for processing. The processed RF data indicates the geolocation information of the ship emitters. The ship emitters may be, for example, any of an S-band ship radar emitter, an X-band ship radar emitter, an L-band communication emitter, a UHF communication emitter, or a VHF communication emitter.

[0165] In some embodiments, a portion of the emitter may be classified as an Emitter of Interest (EOI) imaged by sensors of other sensor types of the ship detection system's satellites. The EOI may be so classified by human intervention and the data transmitted to the ground via the ISL (or may already be on the ground if it is where RF data processing is performed), or the EOI may be automatically classified based on criteria selected by the end user (e.g., all X-band ship radars emitters within X kilometers of a defined coast or landmass).

[0166] The imaging swath width of RF satellite 320 is the widest imaging swath of the imaging satellite and may be greater than 1000 km. RF satellite 320 has no resolution.

[0167] At 412, relay satellite 313 relays the tasking command to wide area SAR satellite 330 via ISL link 334. The particular wide area SAR satellite selected for the task has an accessible swath that overlaps the RF satellite and trails behind RF satellite 320. The tasking command may be modified from the original tasking command created by the mission planning system based on data collected by the RF satellite. For example, the AOI may change based on the geolocation of the EOI, the imaging swath imaged by wide area SAR satellite 330 may be smaller (or larger) than that required by the first command, and the beam mode position of wide area SAR satellite 330 may be changed.

[0168] If a ship expected to be at a particular location is not detected by RF satellite 320, the wide area SAR satellite may image the same location to confirm that the ship is not there or to indicate that the ship is at the expected location but not emitting an RF signal.

[0169] At 414, the wide-area C-band SAR and AIS collector 332 of the wide-area SAR satellite 330 collects the data required by the tasking command. The required data may be an image of the AOI collected by the wide-area C-band collector and AIS information collected by the AIS collector. Similar to the RF satellite 320, the collected data may be processed on board the wide-area SAR satellite 330 or transmitted to a ground terminal for processing via the ISL constellation 310.

[0170] The output of the data processing is a ship detection report. The ship detection report may include the position of the ship detected in the SAR image, the estimated size, course, and speed of the detected ship, the correlation with AIS data if the ship was transmitting (ships not transmitting AIS may be classified or labeled as "dark targets"), the "image chip" of the detected ship, and any one or more of the classification or categorization of the ship as a VOI. The characterization, filtering, prioritization, and position prediction of the VOI may be assisted by an artificial intelligence (AI) or machine learning (ML) model.

[0171] Classifying a ship as a VOI may ensure further imaging of the VOI by the next satellite of the ship detection system. In the embodiments of FIGS. 3 and 4, the next satellite is the next-generation X-band SAR satellite 340. Similar to the classification of the EOI, the classification of the VOI may be done on the ground with human intervention or in an automated manner on board the wide-area SAR satellite 330 (for example, all dark targets within X kilometers from a defined land mass are VOIs).

[0172] The imaging swath width of the wide-area SAR satellite 330 is smaller than the imaging swath of the RF satellite. The imaging swath of the wide-area SAR satellite 330 may be greater than 450 km.

[0173] At 416, the relay satellite 314 transmits a tasking command to the next-generation X-band SAR satellite 340 via the ISL link 344. The specific next-generation X-band SAR satellite 340 selected for the task has an accessible swath that overlaps with the RF satellite 320 and the wide-area SAR satellite 330 and trails behind the wide-area SAR satellite 330. The tasking command may be modified from the original tasking command created by the mission planning system 304 based on data collected by the RF satellite 320 and / or the wide-area SAR satellite 330. For example, the specific swath and beam mode position may be changed based on the specific latitude and longitude positions of the VOI identified by the wide-area SAR satellite.

[0174] If a ship expected to be at a specific location is not detected by the wide-area SAR satellite 330, the next-generation X-band SAR satellite 340 may image the same location to confirm that the ship is not there or to indicate that the ship is at the expected location but is not emitting an RF signal or an AIS signal.

[0175] At 418, the high-resolution X-band SAR collector 342 of the next-generation X-band SAR satellite 340 collects the high-resolution X-band SAR data required by the tasking command. The collected data may be processed on board the next-generation X-band SAR satellite 340 or transmitted to the ground via the ISL constellation 310 for processing.

[0176] The output of the data processing is a ship detection report. The ship detection report may include the position of the ships detected within the SAR image. The ship detection report may include the estimated size, heading, and speed of the detected ships. The ship detection report may include a correlation to the AIS image if the AIS image was collected (ships that do not transmit AIS may be classified as “dark targets”). The ship detection report may include “image chips” of the detected ships. The ship detection report may include a classification of the ships as VOIs. The information is similar to that generated by C-V class SAR satellites, but the data has a higher resolution. Additional ships may be classified as VOIs based on the information in the same manner as described above.

[0177] The imaging swath of the next-generation X-band SAR satellite 340 is smaller than the imaging swath of the wide-area SAR satellite. The imaging swath may be larger than 30 km. The resolution of the next-generation X-band SAR satellite 340 is higher than that of the wide-area SAR satellite.

[0178] At 420, the relay satellite 315 transmits a tasking command to the optical satellite 350 via the ISL link 354.

[0179] The particular optical satellite 350 selected for the task has an accessible swath that overlaps with the RF satellite, the wide-area SAR satellite, and the next-generation X-band SAR satellite, and trails directly behind the next-generation X-band SAR satellite (in the constellation).

[0180] The tasking command may be modified from the original tasking command created by the mission planning system 304 based on data collected by the RF satellite, the wide-area SAR satellite, and / or the next-generation X-band SAR satellite. For example, the angle of capture within the field of regard of the optical satellite 350 may be changed based on the specific latitude and longitude positions of the VOIs identified by the wide-area SAR satellite and the next-generation X-band SAR satellite.

[0181] At 422, the high-resolution optical collector 352 of the optical satellite 350 collects the high-resolution optical data required by the tasking command. The high-resolution optical data includes at least one high-resolution optical image of one VOI or multiple VOIs.

[0182] The imaging swath width of the optical satellite 350 is smaller than the imaging swath of the next-generation X-band SAR satellite. The imaging swath width can be greater than 5 km. The resolution of the optical satellite 350 is higher than that of the next-generation X-band SAR satellite.

[0183] The optical satellite 350 transmits the high-resolution optical image to the relay satellite 316 of the ISL constellation 310.

[0184] At 424, the relay satellite 316 transmits the information collected from all of the satellite collectors 322, 332, 342, 352 to the end-user receiving system 360. The end-user receiving system 360 can be on-site or off-site, can be the end-user command system 302, or can be other than the end-user command system 302. The end-user who receives the output of the ship detection process can be the same as or different from the end-user who issued the command.

[0185] The latency (interval) during data acquisition by the imaging satellite is based on how quickly the processing, utilization, and tasking of the next satellite can be performed.

[0186] In other embodiments, imaging satellites of different sensor types may be employed.

[0187] In other embodiments, clusters of imaging satellites may be employed.

[0188] Referring next to FIG. 5, shown there is Example 500 of an embodiment of the specific ship detection system and method of FIGS. 3 and 4 according to an embodiment.

[0189] System 500 includes a space segment 501 and a ground segment 503. The ground segment 503 includes an end-user command system 502, a mission planning system 504, and an end-user receiving system 506. The space segment 501 includes an inter-satellite link (ISL) relay constellation 510 and a constellation of four imaging satellites including an RF satellite 520, a wide-area SAR satellite 530, a next-generation X-band SAR satellite 540, and an optical satellite 550.

[0190] Also, the ground segment may include at least one command system for inputting commands, at least one spacecraft control system for controlling at least one spacecraft, and at least one data chain system for managing data.

[0191] The ISL relay constellation includes relay satellites 511, 512, 513, 514, 515, and 516 representing a subset of the satellites of the ISL relay constellation. In other embodiments, the ISL relay 510 may include even more satellites on the order of hundreds of satellites in some cases. In the embodiments of FIGS. 3, 4, and 5, each relay satellite communicates with only two imaging satellites, and each imaging satellite communicates with only two relay satellites. In some embodiments, multiple relay satellites may be responsible for a single step of the ship detection method.

[0192] The RF satellite 520 has an imaging swath 526. In an exemplary embodiment, the imaging swath 526 may be greater than 1000 km.

[0193] The Class C-V SAR satellite 530 has an imaging swath 536. In an exemplary embodiment, the imaging swath 536 may be greater than 500 km.

[0194] The next-generation X-band SAR satellite 540 has an imaging swath 546. In an exemplary embodiment, the imaging swath 546 may be greater than 30 km.

[0195] Optical satellite 550 has imaging swaths 556. In an exemplary embodiment, the imaging swaths 556 may be greater than 5 km.

[0196] Imaging swaths 526, 536, 546, and 556 are simplified representations of the actual imaging swaths, intended to represent areas where the imaging swaths of the satellites overlap. As discussed above, the imaging satellites have been shown to be on exactly the same ground track 558, but the imaging satellites may not have the same ground track. However, the ground tracks must be close enough that the satellites have overlapping accessible swaths.

[0197] Imaging satellites 520, 530, 540, and 550 are all shown as nadir satellites in FIG. 5 for simplicity. However, different types of satellites, including the type shown and discussed in FIG. 5, may actually be side-looking satellites.

[0198] Since FIG. 5 is a time series of a leading satellite and a trailing satellite passing over the AOI, the imaging swaths 526, 536, 546, and 556 shown in FIG. 5 are intended to convey that the satellites are imaging the same area at different times.

[0199] A horizontal dashed line is used to separate the space segment 501 (top) of the ship detection system 500 from the ground segment 503 (bottom).

[0200] Here, an exemplary operation sequence executed by the system 500 will be described.

[0201] At 560, the command is sent from the end-user command system 502 via the uplink to the relay satellite 511 of the ISL layer 510. The relay satellite 511 (any other satellite of the ISL layer 510) may be in LEO, MEO, or GEO. The input is the command specified by the user. The content of the command may be specified by the user, for example, through the user interface of the end-user command system 501 or a user interface communicating with the end-user command system 501.

[0202] The command may include an area of interest ("AOI"). The AOI defines the area where sensor data collection should be performed. In some embodiments, the AOI may be specified as a defined area polygon. A command specifying the AOI may be referred to as an "area-based command". In other embodiments, the command may specify one or more individual collection swaths. The individual collection swaths may be selected by the user, for example, in the end-user command system 502. In some cases, the end-user command system 502 may display a list of available swaths that are selectable for inclusion in the command. In some cases, the list of available swaths may be a subset of swaths determined according to some filtering criteria. The filtering criteria may be selected by the user or determined based on user input in the end-user command system 502. In an example, the filtering criteria may be a date range. The user may enter a date range in the end-user command system 502, and the end-user command system 502 determines and displays a list of available swaths based on the specified date range. Then, the user may select an available imaging swath width, and the end-user command system 502 includes the selected imaging swath width in the command. A command specifying the imaging swath width may be referred to as a "swath-based command".

[0203] The command may include a date range.

[0204] The instruction may include one or more desired modes.

[0205] The instruction may specify the type of sensor from which data is to be collected. In embodiments, the sensor type may include RF sensing, wide area C-band SAR, AIS, X-band SAR, and optical sensing. The instruction may specify all sensor types, or some subset of sensor types (e.g., RF, C-band SAR, and X-band SAR only).

[0206] The instruction may include a destination. The destination specifies the receiving device that is to receive the output of the vessel detection operation. The destination may include a device identifier that can be used by the transmitting device to direct the output to the receiving device. For example, in the case of FIG. 5, the destination is the end-user receiving system 506. The destination can be various. The end-user receiving system 506 may be associated with the same user as the end-user instruction system 502. The end-user receiving system 506 may be the same device as the end-user instruction system 502. The end-user receiving system 506 may be associated with a user different from the instruction user. The end-user receiving system 506 may be on-site or not.

[0207] The ISL layer 510 may provide connectivity between the end-user instruction system 502 and the mission planning system 504. The connectivity enables an instruction to be issued from any user location on the earth at any time (i.e., the end-user instruction system 502 may be anywhere on the earth).

[0208] The relay satellite 511 (and other satellites of the ISL relay layer 510) may be in LEO, MEO, or GEO.

[0209] At 562, the command is transmitted from the relay satellite 511 of the ISL layer 510 to the mission planning system 504 via the downlink. The mission planning system 504 may be a cloud-based ground segment (mission planning system). The downlink receiving station antenna of the mission planning system 504 may be known in advance.

[0210] In some cases, before the command is provided to the mission planning system 504 of the ground segment 503, the command may "hop" between multiple different satellites of the ISL relay constellation 510.

[0211] In some cases, the receiving station receives the command and transmits the command to a cloud-based mission planning system (ground segment, for example, part of the AWS GS Central Processing Region). The mission planning system 504 may be configured to check the availability of satellite resources of each sensor of the system (for example, the availability of satellites 520, 530, 540, 550) and plan actual collection and spacecraft tasking commands. The mission planning system 504 is configured to generate one or more spacecraft / satellite tasking commands based on the information included in the received command.

[0212] At 564, the mission planning system 504 transmits the tasking command to the relay satellite 510 of the ISL layer 510 via the uplink. The tasking command includes spacecraft tasking information used to task each sensor of the system 500. The tasking command may be one or more commands depending on the nature of the command and the number of sensors used.

[0213] The tasking commands include the initial spacecraft tasking for the wide area RF collector of the RF satellite 520, the SAR collector of the wide area SAR satellite 530, the SAR collector of the X-band SAR satellite 540, and the optical collector of the optical satellite 550. The initial spacecraft tasking commands may include the overall direction indicated by each of the satellites 520, 530, 540, and 550. The initial tasking commands may also include specific imaging coordinates for imaging as each satellite passes over the coordinates. If the initial tasking commands for any of the trailing satellites include imaging coordinates, the coordinates may be modified during operation based on data collected and processed by the leading satellite.

[0214] In 566, the relay satellite 512 of the ISL layer 510 transmits tasking commands to the wide area RF satellite 520. The tasking commands for the wide area RF collector received in 566 may indicate the area and time (based on the command) in which the user wishes to identify the geographical location of the RF emitter.

[0215] At 568, RF satellite 520 collects RF signals (RF data) over a specified AOI (specified and then specified by a tasking command). RF satellite 520 may use an on-board processor to analyze or parse the received tasking command (e.g., to identify a specified area of interest) and generate RF sensor command data. The RF sensor command data is sent to the RF sensor, which causes the RF sensor to collect RF signals over the AOI. The collected RF signals may be considered raw RF sensor data. In some cases, the RF data is processed on board RF collector satellite 520 by the on-board processor. In other cases, the RF data may be sent via the ISL layer 510 to the ground segment 503 for ground processing (in the ground processing system or ground terminal shown in FIG. 1A). Generally, the raw RF data is processed to determine the geolocation information of the RF-emitting vessel. In either case, the RF data is processed to obtain one or more processed data products that include the geolocation information of RF emitters detected within the scene over one or more frequency bands. For example, in some embodiments, the RF emitter may be detected by any one or more of an S-band marine radar, an X-band marine radar, an L-band communication, a UHF communication, and a VHF communication.

[0216] During the processing of RF data, some of the detected RF emitters may be categorized or classified as "emitters of interest" (EOIs), and the EOIs ensure further imaging by other subsequent sensors (e.g., by the sensors of satellites 530, 540, and 550). In some cases, the EOI categorization process may be performed with human intervention. Such processing may use the hop of ISL 510 to the ground segment 503, or may already be on the ground 503 if the processing of the collected RF data is being performed by the ground processing system of the ground segment 503. In some cases, the EOI categorization process may be performed in an automated manner based on criteria selected by the user. Examples of criteria selected by the user are all X-band marine radar emitters within x kilometers from a defined coast or landmass. Other types of criteria selected by the user will be obvious. The criteria selected by the user may be received via the user interface of the end-user command system 502 (e.g., when a command is generated). The criteria selected by the user may be used to effectively filter the detected RF emitters with respect to the RF emitters (EOIs) that meet the criteria selected by the user. With automated EOI selection, the EOI filtering process may be performed on board the RF collector spacecraft 520 or on the ground 503.

[0217] In some cases, if no EOIs are identified within the RF data, the area collected by the RF satellite 520 may be imaged again by the subsequent C-band SAR satellite 530. For example, a tasking command may be automatically generated to command the C-band SAR satellite 530 to image the same AOI if it is determined that there are no detected EOIs, and such a tasking command is transmitted to the C-band SAR satellite 530 via the ISL layer 510.

[0218] At 570, the RF satellite 520 transmits cross - cueing information or cross - cueing data including geolocation information to the satellite 513 of the ISL layer 510. The cross - cueing information includes command and tasking information for the wide - area SAR satellite 530 and may include additional related information such as VOI information.

[0219] At 572, the relay satellite 513 of the ISL layer 510 transmits command and tasking information to the wide - area SAR satellite 530. The wide - area SAR satellite 530 includes an on - board wide - area C - band SAR collector and an AIS collector.

[0220] The command and tasking information relayed from the satellite 513 to the C - band SAR satellite 530 includes command and tasking information (e.g., AOI polygon or available swaths, imaging time, beam mode) based on the collection results of the RF satellite 520. For example, the processed data product generated based on the RF data collected by the RF satellite 520 may identify 10 EOIs within the RF scene at the corresponding latitude and longitude positions. To cross - cue and capture those 10 EOIs in the C - band SAR image, a specific swath (e.g., 450 km wide ship detection mode) at a specific beam - mode position (e.g., near - range or far - range - i.e., how far away from directly below) may be required. The command and tasking information may be the same as the initial tasking command transmitted by the mission - planning system 504 while additional data collected by the RF satellite 520 is added, or the initial tasking command may be modified. For example, if the initial coordinates are received from the mission - planning system 504, those coordinates may be changed based on the data collected by the RF satellite 520.

[0221] In some cases, although a vessel of interest (VOI) was expected at a certain location, it was not detected by the RF satellite 520 (for example, either because the vessel was not there or it was not emitting an RF signal). The C-band SAR collector satellite 530 may image the same location to confirm the presence or absence of that VOI.

[0222] At 574, the C-V SAR satellite 530 uses an on-board wide-area C-band SAR collector and AIS collector to image over a specified AOI. The C-band satellite 530 may include both a primary SAR payload and a secondary AIS payload in the coincident imaging scene. The SAR sensor collects C-band SAR data and the AIS collector collects AIS data. Such collected data may be referred to as raw C-band SAR data and raw AIS data. And the raw SAR and AIS data are processed to obtain one or more processed data products. In some cases, the SAR and AIS data are processed on-board the wide-area C-band and AIS collector satellite 530 by an on-board processor. In other cases, the SAR and AIS data may be transmitted via the ISL layer 510 to the ground processing system (shown in FIG. 1A) of the ground segment 503 for ground processing.

[0223] The processed data product includes one or more ship detection reports. The ship detection report may include the position data of the ships detected in the SAR image. The ship detection report may include the estimated size, direction of travel, and speed of each detected ship. The ship detection report may include a correlation with AIS (if the identified ship is not transmitting AIS, the ship may be classified as a "dark target"). The ship detection report may include an "image chip" of the detected ship. The image chip may resemble a cropped thumbnail showing the actual ship within the SAR image. The ship detection report (or some subset of the data therein) may be considered cross-querying data used by the system to cross-query subsequent sensor data collection (e.g., by satellite 540).

[0224] Processing C-band SAR and AIS data may involve categorizing or classifying some identified vessels as "vessels of interest" (VOIs), where the VOIs warrant further imaging by other subsequent sensors (e.g., by the sensors of satellites 540 and 550). In some cases, the VOI classification process may be performed with human intervention. Such processing may use hops of ISL 510 to the ground segment 503, or may already be on the ground if the processing of the collected C-band SAR data and AIS data is performed by the ground processing system of the ground segment 503. In some cases, the VOI categorization process may be performed in an automated fashion based on criteria selected by the user. Examples of criteria selected by the user are "all dark targets within x kilometers from a defined coast or landmass". Other types of criteria selected by the user will be apparent. The criteria selected by the user may be used to effectively filter the detected vessels with respect to the vessels (VOIs) that meet the criteria selected by the user. With automated VOI selection, the VOI filtering process may be performed on board the C-band SAR spacecraft 530 or on the ground 503. The vessel detection onboard processing (VDOP) may be similar to the process described in PCT / CA2021 / 051298 as discussed above.

[0225] At 576, the C-band SAR and AIS collector satellite 530 transmits cross-queuing data (e.g., processed data products including one or more vessel detection reports) to the relay satellite 514 of the ISL layer 510.

[0226] At 578, the relay satellite 514 of the ISL layer 510 transmits commands and tasking information to the (high-resolution) X-band SAR satellite 540. The X-band SAR satellite 540 includes an on-board X-band SAR collector.

[0227] The commands and tasking information relayed from satellite 514 to the X-band SAR satellite 540 include commands and tasking information appropriately modified by the collection results of the C-band SAR and AIS collector satellite 530, as well as data collected by the satellite (e.g., AOI polygon or available swaths, imaging time, beam mode). For example, the processed data products generated based on the C-band SAR data (and AIS data) collected by the C-band SAR satellite 530 may identify 10 VOIs within the C-band SAR scene at the corresponding latitude and longitude positions. The 10 VOIs may cover a specific area. To cross-cue and capture those 10 VOIs in the X-band SAR image, a specific swath (e.g., 3m stripmap mode) at a specific beam mode position (e.g., near or far distance - i.e., how far away from directly below) may be required.

[0228] In some cases, if a vessel of interest (VOI) was expected at a location but was not detected by the wide-area C-band SAR and AIS collector satellite 530 (either because the vessel was not there, or was too small to be detected and was dark (i.e., not transmitting AIS)), the high-resolution X-band SAR collector satellite 540 may image the same location to confirm the presence or absence of that VOI.

[0229] At 580, the X-band satellite 540 images over the specified AOI using an on-board X-band SAR collector. The X-band SAR satellite 540 processes the collected X-band SAR data (raw SAR data) by an on-board processor to obtain a processed data product. The processed data product includes one or more ship detection reports. The ship detection report may include the position data of the ships detected in the SAR image. The ship detection report may include the estimated size, heading, and speed of each detected ship. The ship detection report may include an "image chip" of the detected ship. The image chip may resemble a cropped thumbnail showing the actual ship in the SAR image. Note that the SAR data collected by the X-band SAR satellite 540 and the processed data product (including the ship reports) generated therefrom are of higher resolution than the SAR data collected by the wide-area C-band SAR satellite 530, thanks to the X-band SAR beam mode selection and the estimated position of the VOI from the previous sensor (i.e., the sensor on board the C-band SAR satellite 530). The estimated position of the VOI is generated based on the C-band SAR data and is specified in the processed data product (ship detection report) used by the X-band SAR satellite 540 when collecting the X-band SAR data. The ship detection report (or some subset of the data therein) may be considered cross-queuing data used by the system to cross-queue subsequent sensor data collection (e.g., by satellite 550).

[0230] Processing X-band SAR data may involve categorizing or classifying some identified vessels as "vessels of interest" (VOIs), where the VOIs warrant further imaging by other subsequent sensors (e.g., by the sensors of satellite 550). In some cases, the classification of VOIs may be performed with human intervention. Such processing may use a hop of ISL 510 to the ground segment 503 or may already be on the ground if the processing of the collected X-band SAR data is being performed by the ground processing system of the ground segment 503. In some cases, the VOI categorization process may be performed in an automated form based on criteria selected by the user. Examples of criteria selected by the user are "all vessels within x kilometers from a defined coast or landmass". Other types of criteria selected by the user will be apparent. The criteria selected by the user may be used to effectively filter detected vessels with respect to vessels (VOIs) that meet the criteria selected by the user. With automated VOI selection, the VOI filtering process may be performed on board the X-band SAR spacecraft 540 or on the ground 503. The VDOP may be similar to the process described in PCT / CA2021 / 051298 as considered above.

[0231] In some cases, the X-band SAR satellite 540 may generate direct tasking commands for the subsequent high-resolution optical collector satellite 550, based entirely on the VOIs detected in the prior high-resolution X-band SAR data.

[0232] At 582, the X-band SAR collector satellite 540 transmits cross-queuing data (e.g., processed data products including one or more vessel detection reports) to the relay satellite 515 of the ISL layer 510.

[0233] The incorporation of the ISL relay layer 510 eliminates the need for round-trip time to the ground station mask, enabling a faster cross-link process including the latency of intermediate satellites, thanks to the shorter latency and the availability of NRT communication. Furthermore, tasking is done not only via the ground but also through the ISL relay link 510, which may enable faster tasking. For example, a trailing high-resolution X-band SAR collector satellite may be tasked directly from the ISL relay layer based on the VOI detected by the wide-area C-band SAR and AIS collectors.

[0234] In 584, the relay satellite 515 of the ISL layer 510 transmits commands and tasking information to the optical collector satellite 550. The optical collector satellite 550 includes an on-board optical sensor for collecting optical image data.

[0235] The commands and tasking information relayed from the satellite 515 to the optical satellite 550 include the commands and tasking information passed from the original commands, appropriately modified by the collection results of the X-band SAR collector satellite 540 (e.g., AOI polygon or available swaths, imaging time). For example, the processed data product generated based on the X-band SAR data collected by the X-band SAR satellite 540 may identify 10 VOIs within the X-band SAR scene at the corresponding latitude and longitude positions. The 10 VOIs may cover a specific area. A specific off-nadir angle within the dynamic field of view of the optical satellite 550 may be required to cross-queue and capture those 10 VOIs in the optical image.

[0236] In 586, the high-resolution optical collector satellite 550 uses on-board optical sensors to image over a specified AOI and generate one or more high-resolution optical images of one or more VOIs within the AOI. The optical satellite 550 may generate data products processed by an on-board processor. The processed data products may include one high-resolution optical image or multiple high-resolution optical images. The processed data products may be in the form of a ship detection report as described herein. The processed data products may include data from any of the previously generated processed data products (e.g., by satellites 520, 530, 540).

[0237] In 588, the processed data products containing high-resolution optical image data are transmitted from the optical satellite 550 to the relay satellite 516 of the ISL layer 510.

[0238] In 590, the processed data products are transmitted from the relay satellite 516 of the ISL layer 510 to the end-user receiving system 506 via a downlink for consumption by an end-user or customer.

[0239] Note that in system 500, the output from the optical satellite 550 or any previous sensor (e.g., from any of satellites 520, 530, 540) can be transmitted from the ISL relay layer 510 to an end-user who may or may not be located on-site (i.e., to the end-user receiving system 506 which may or may not be on-site).

[0240] Considering that the ISL layer 510 can provide continuous connectivity between the sensors of satellites 520, 530, 540, 550 and the end-users, sensor products generated based on the data collected by satellites 520, 530, 540, 550 may be provided to any user location on Earth at any time.

[0241] Next, referring to FIG. 6, shown therein is a method 600 for data collection for maritime surveillance according to an embodiment. The method 600 may be implemented using, for example, the system 100 of FIG. 1 or the system 500 of FIG. 5.

[0242] At 602, the method 600 includes collecting first type of remote sensing data by a first remote sensing payload on a first Earth Observation (EO) satellite.

[0243] At 604, the method 600 includes cross-connecting to a second EO satellite to collect second type of remote sensing data by a second remote sensing payload on the second EO satellite via an inter-satellite link relay layer including at least one relay satellite, wherein the cross-connecting is based on the first type of remote sensing data collected by the first EO satellite, the second EO satellite has an accessible swath overlapping with the first EO satellite, and the second remote sensing payload has a narrower imaging swath than the first remote sensing payload.

[0244] At 606, the method 600 further includes collecting second type of remote sensing data by the second remote sensing payload on the second EO satellite, wherein the collecting is based on the first type of remote sensing data.

[0245] At 608, the method 600 includes cross-connecting to a third EO satellite to collect third type of remote sensing data via the inter-satellite link relay layer, wherein the cross-connecting is based on the second type of remote sensing data collected by the second EO satellite, the third EO satellite has an accessible swath overlapping with the first EO satellite and the second EO satellite, and the third remote sensing payload has a narrower imaging swath than the second remote sensing payload.

[0246] At 610, method 600 is to collect third type of remote sensing data by a third remote sensing payload on a third EO satellite, the collection further including collecting based on the second type of remote sensing data.

[0247] FIG. 7 is an exemplary satellite image generated by the system of the present disclosure, showing a polygon area (AOI) and a single remote sensing swath superimposed on the image.

[0248] Image 700 shows a satellite image over North America, together with a box 702 representing the area of interest (AOI) 702 to be monitored and a remote sensing swath 704 of the satellite. The remote sensing swath 704 is within the AOI 702. Each imaging satellite tasked with monitoring the AOI has an overlapping accessible swath width, and each of the accessible swath widths overlaps with the AOI 702. The first remote sensing satellite may have a remote sensing swath that covers the entire AOI, and each subsequent remote sensing satellite adjusts the location of the remote sensing swath within the AOI based on the remote sensing data collected by the previous remote sensing satellite. For example, the first remote sensing satellite may be positioned approximately centrally within the AOI 702 and may have collected remote sensing data covering the entire AOI 702, and the remote sensing data of each subsequent remote sensing satellite is such that the remote sensing satellite capturing the remote sensing swath 704 adjusts the remote sensing swath of the subsequent remote sensing satellite so as to be tasked with capturing a specific area (a small area off the center of the AOI 702) shown in FIG. 7.

[0249] The above description provides examples of one or more devices, methods, or systems, but it will be understood that other devices, methods, or systems may be included within the scope of the claims as interpreted by those skilled in the art. Description of Reference Signs

[0250] 100 Ship Detection System 102 Command System 104 Mission Planning System 106 Receiving System 108 Ground Terminal 110 Inter-Satellite Link Relay Layer (ISL Relay Layer) 120 First Imaging Satellite 122 Collector of the First Sensor Type 124 ISL, ISL Link 130 Second Imaging Satellite 132 Collector of the Second Sensor Type 134 ISL, ISL Link 140 Third Imaging Satellite 142 Collector of the Third Sensor Type 144 ISL, ISL Link 150 Fourth Imaging Satellite 152 Collector of the Fourth Sensor Type 154 ISL, ISL Link 200 Method 300 Ship Detection System 302 End-User Command System, Operating System 304 Mission Planning System 306 End-User Receiving System 310 Inter-Satellite Link Relay Constellation (ISL Relay Constellation) 311 Satellite, Relay Satellite 312 Satellite, Relay Satellite 313 Satellite, Relay Satellite 314 Satellite, Relay Satellite 315 Satellite, Relay Satellite 316 Satellite, Relay Satellite 320 RF Satellite 322 Wide-Area RF Collector, Satellite Collector 324 ISL, ISL Link 330 Wide-Area C-Band SAR Satellite, Wide-Area SAR Satellite 332 Wide Area C-Band SAR and AIS Collector, Satellite Collector 334 ISL, ISL Link 340 High-Resolution X-Band SAR Satellite, Next-Generation X-Band SAR Satellite 342 High-Resolution X-Band SAR Collector, High-Resolution X-Band SAR Collector 344 ISL, ISL Link 350 Optical Satellite 352 High-Resolution RF Collector, High-Resolution Optical Collector 354 ISL, ISL Link 360 End-User Receiving System 400 Method 500 Example, System, Ship Detection System 501 Space Segment 502 End-User Command System 503 Ground Segment 504 Mission Planning System 506 End-User Receiving System 510 Inter-Satellite Link Relay Constellation, ISL Layer, ISL Relay Link 511 Relay Satellite 512 Relay Satellite 513 Relay Satellite 514 Relay Satellite 515 Relay Satellite 516 Relay Satellite 520 RF Satellite, RF Collector Spacecraft 526 Imaging Swath 530 Wide Area SAR Satellite, C-Band SAR Spacecraft, C-Band SAR Collector Satellite, C-V SAR Satellite, AIS Collector Satellite 536 Imaging Swath 540 Next-Generation X-Band SAR Satellite, X-Band SAR Spacecraft, X-Band SAR Satellite 546 Imaging Swath 550 Optical Satellite, High-Resolution Optical Collector Satellite, Optical Collector Satellite 556 Imaging Swath 558 Ground Track 600 Method 700 Image 702 Area of Interest (AOI) 704 Remote Sensing Switch

Claims

1. 1. A system for enhanced vessel detection at sea, comprising: a ground segment including a mission planning system configured to receive vessel detection commands from a command device and generate a set of tasking commands based on said commands, each tasking command including a set of coordinates for data collection by a satellite; an inter-satellite link (ISL) relay layer including a plurality of relay satellites in earth orbit, the ISL relay layer configured to receive the set of tasking commands from a mission planning subsystem; A plurality of earth observation satellites having overlapping accessible swaths, a first earth observation satellite having a first sensor and a first imaging swath width, the first earth observation satellite being configured to receive a first tasking command from the set of tasking commands, the first tasking command including a first set of coordinates, collect first sensor data at the first set of coordinates, and transmit the first sensor data to the ISL relay layer; a set of trailing Earth observation satellites including at least a second Earth observation satellite, the second Earth observation satellite having a second sensor and a second imaging swath width, the second Earth observation satellite trailing behind the first Earth observation satellite on the same ground track as the first Earth observation satellite, the second Earth observation satellite being configured to receive a second tasking command including a second set of coordinates from the ISL relay layer, collect second sensor data at the second set of coordinates, and transmit the second sensor data to the ISL relay layer, the second set of coordinates being based on the first sensor data; a receiving system for receiving ship detection data from the ISL relay layer, the ship detection data including the first sensor data and the second sensor data, the ship detection data being processed to generate at least one ship detection report; Including, the system.

2. 2. The system of claim 1, wherein the vessel detection report includes at least one of a position of the at least one vessel, an estimated size of the at least one vessel, a heading of the at least one vessel, a speed of the at least one vessel, an AIS data correlation of the at least one vessel, an image chip of the at least one vessel, and a vessel of interest (VOI) classification of the at least one vessel.

3. 2. The system of claim 1, wherein the set of trailing Earth observation satellites further includes N Earth observation satellites each trailing in sequence behind the second Earth observation satellite, N being any positive integer, each of the N Earth observation satellites having a respective sensor and a respective imaging swath width, and each of the N Earth observation satellites configured to receive a respective tasking command from N tasking commands sent by the mission planning system to the ISL relay layer, collect respective sensor data based on the respective tasking command, and send the respective sensor data to the ISL relay layer.

4. The system of claim 3 , wherein the second tasking command is modified based on the first sensor data.

5. 4. The system of claim 3, wherein the ISL relay layer receives the N respective tasking commands from the mission planning system before the first sensor data is collected and transmitted to the ISL relay layer.

6. 6. The system of claim 5, wherein each of the N respective tasking commands is modified based on data from an Earth observation satellite followed by each of the N Earth observation satellites.

7. The system of claim 1 , wherein the ground segment further includes at least one spacecraft control system configured to control and maintain operation of any of the plurality of Earth observation satellites.

8. 13. The system of claim 1, wherein the ground segment further comprises at least one data chain subsystem configured to receive image data from at least one ground terminal and reconstruct the image data into raw data for processing into a product.

9. 2. The system of claim 1, wherein at least one of the first sensor data and the second sensor data is transmitted via the plurality of relay satellites to a ground terminal of the ground segment for processing by the ground terminal.

10. The system of claim 1 , wherein the second Earth observation satellite has a smaller swath width and higher resolution than the first Earth observation satellite.

11. 4. The system of claim 3, wherein each of the N earth observation satellites has a smaller swath width and higher resolution than a previous earth observation satellite.

12. 1. A method of maritime surveillance comprising: receiving, via a network interface or an input interface of the ground segment mission planning system, a maritime surveillance command from the command device; generating, by a processor of the mission planning system, a plurality of tasking commands based on the instructions, each tasking command including a set of coordinates for a satellite; transmitting the plurality of tasking commands as RF signals to an inter-satellite link (ISL) relay layer via an antenna system of the ground segment; transmitting, by an antenna system of the ISL relay layer, a first tasking command of the plurality of tasking commands to a first Earth observation satellite, the first tasking command including a first set of coordinates; collecting first remote sensing data at the first set of coordinates received from the ISL relay layer by a first sensor of the first Earth observation satellite having a first remote sensing swath width, and transmitting the first remote sensing data to the ISL layer via an antenna system of the first Earth observation satellite; cross-queuing, via the ISL relay layer, to at least a second Earth observation satellite to collect second remote sensing data at a second set of coordinates using a second sensor having a second remote sensing swath width, wherein cross-queuing is based on a second tasking command and the first remote sensing data, the first Earth observation satellite and the second Earth observation satellite have overlapping accessible swath widths, and the second Earth observation satellite follows the first Earth observation satellite on the same ground track; transmitting the second remote sensing data to the ISL relay layer via an antenna system of the second Earth observation satellite; transmitting maritime surveillance information as an RF signal via the antenna system of the ISL relay layer to a receiving system of the ground segment for display on an end user device of the ground segment; displaying at least one vessel detection report generated from the maritime surveillance information on a graphical user interface of an end user device.

13. 13. The method of claim 12, further comprising: cross-queuing, via the inter-satellite link relay layer, N earth observation satellites to collect respective remote sensing data, where N is any positive integer, each of the N earth observation satellites trailing in sequence behind the second earth observation satellite, cross-queuing for each of the N earth observation satellites is based on a respective tasking command and remote sensing data from each of the earth observation satellites that each respective N earth observation satellite is trailing, each of the N earth observation satellites having an Nth remote sensing swath width, and each of the N earth observation satellites having an accessible swath width that overlaps with the first earth observation satellite and the second earth observation satellite.

14. 13. The method of claim 12, further comprising at least one spacecraft control system configured to control any of a plurality of Earth observation satellites.

15. 13. The method of claim 12, further comprising at least one data chain subsystem configured to receive image data from at least one ground terminal and reconstruct the image data into raw data for processing into a product.

16. The method of claim 12 , wherein the second Earth observation satellite has a smaller swath width and higher resolution than the first Earth observation satellite.

17. 13. The method of claim 12, wherein each of the N earth observation satellites has a smaller swath width and higher resolution than a previous earth observation satellite.

18. 1. A method of vessel detection at sea, comprising: tasking a wide area radio frequency (RF) collector satellite to collect RF signals from the ship-based emitter from an area at a first set of coordinates defined by a first tasking command; collecting RF data at the first set of coordinates using an RF collector on the wide area RF collector satellite; using collected RF data to determine a geolocation of a vessel emitter within the region, the geolocation being defined by coordinates, the vessel emitter being a vessel of interest (VOI); cross-queuing a C-band SAR satellite to collect C-band SAR data for the VOI using the geolocation as a second set of coordinates through an ISL relay layer including a plurality of relay satellites, the C-band SAR satellite having an accessible swath that overlaps with the wide area RF collector satellite; collecting C-band SAR data and AIS data at the second set of coordinates using the C-band SAR satellite, the AIS data being used to identify the VOI; cross-queuing, through the ISL relay layer, an X-band SAR satellite to collect X-band SAR data for the VOI, the C-band SAR data determining a third set of coordinates, the X-band SAR satellite having an accessible swath that overlaps with the wide area RF collector satellite and the C-band SAR satellite; collecting X-band SAR data at the third set of coordinates using the X-band SAR satellite; cross-queuing, through an ISL relay layer, an optical satellite to collect optical image data of a VOI, the X-band SAR data determining a fourth set of coordinates, the optical satellite having an accessible swath overlapping with the wide area RF collector satellite, the C-band SAR satellite, and the X-band SAR satellite; collecting optical image data of the VOI at the fourth coordinate using the optical satellite; downlinking sea vessel detection data including at least the optical image data to a ground segment by one of the optical satellite and the ISL relay layer.

19. 20. The method of claim 18, wherein the marine emitter may be one of an S-band marine radar emitter, an X-band marine radar emitter, an L-band communications emitter, a UHF communications emitter, or a VHF communications emitter.

20. 20. The method of claim 18, wherein ship detection reports are transmitted to the ground segment via the ISL relay layer for at least one of the wide area RF collector satellites, the C-band SAR satellites, the X-band SAR satellites, and the optical satellites, and the ship detection reports include at least one of a position of at least one vessel, an estimated size of at least one vessel, a heading of at least one vessel, a speed of at least one vessel, an AIS data correlation of at least one vessel, an image chip of at least one vessel, and a vessel of interest (VOI) classification of at least one vessel.

Images