Method, system and satellite for detecting objects in space

Abstract

The present invention relates to detecting objects in space. In particular, the present invention relates to a method for detecting objects and a corresponding system. The system for detecting objects (12) in space comprises a satellite constellation (100) comprising a number of satellites (110) orbiting around a planet or natural satellite in a line formation, each of the number of satellites (110) comprising a detection device (112) and on-board processing circuitry (114) coupled to the detection device (112). The satellite constellation (100) is configured to monitor the space using the respective detection device (112) and on-board processing circuitry (114) of at least part of the number of satellites (110) to detect one or more objects (12) in space.

Description

[0001] Method, system and satellite for detecting objects in space

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention generally relates to detecting objects in space. In particular, the present invention relates to a method for detecting objects in space, a system for detecting objects in space, a satellite for detecting objects in space, a non- transitory machine-readable medium, and a computer program. Further, the present invention relates to the use of a satellite constellation.

[0004] TECHNICAL BACKGROUND

[0005] In space, e.g. in the Earth's orbits, there is a growing number of active objects, e.g. operational satellites or the like, and inactive objects, e.g. abandoned rocket bodies, debris, etc. In view of increasing involvement of actors in space, such as commercial and governmental mega constellations of satellites, or the like, the growing number of objects results in a need for detailed, timely and accurate insights into objects in various orbits.

[0006] In this context, Space Situational Awareness (SSA) is thus a topic of relevance for e.g. satellite operators and the wider space ecosystems, including both commercial and governmental and / or institutional actors. SSA refers to the knowledge of the current state of the near-Earth space environment. Space domain awareness (SDA) refers to studying and / or monitoring of satellites orbiting the Earth. It comprises the detection, tracking, cataloging and identification of artificial objects, i.e. active and / or inactive satellites, abandoned rocket bodies, or debris. As a subset of capabilities within SSA and / or SDA, Space Surveillance and Tracking (SST) and Space Traffic Management (STM) are commonly referred to. An SST system consists of a number of on-earth and / or in-space sensors, which are detecting and tracking space objects, and computing capabilities - networking, storage, processing, etc. - to provide information about space objects and their orbits around the Earth as data products or services.

[0007] In view of the growing number of objects in space, there is a need for improved means for detecting objects in space in a reliable and / or early manner.

[0008] SUMMARY OF THE INVENTION

[0009] Hence, an object of the present invention is to provide improved means for detecting objects in space.

[0010] This object is solved by the subject-matter of the independent claims. Further embodiments and advantages are set out in the dependent claims as well as the following description.

[0011] According to a first aspect, there is provided a method for detecting objects in space. The method comprises forming a satellite constellation. The satellite constellation comprises a number of satellites orbiting around a planet or natural satellite in an at least approximated line formation. Each of the number of satellites comprises a detection device and on-board processing circuitry coupled to the detection device. Further, the method comprises monitoring of the space using the respective detection device and on-board processing circuitry of at least part of the number of satellites to detect one or more objects in space.

[0012] The method may be used for carrying out and / or providing Space Domain Awareness (SDA) and / or related tasks, such as Space Surveillance and Tracking (SST) and Space Traffic Management (STM). The satellite constellation equipped with the detection devices and formed to orbit in the at least approximated line formation allows for forming an in-space detection fence. In contrast to a stationary ground-based detection, which is able to detect an orbiting object in space only at certain orbits due to the rotation of the Earth, a satellite constellation as disclosed herein is able to detect or spot the same object twice per orbit. Typical satellites in orbit, e.g. low earth orbit (LEO), orbit the earth between 14 to 16 tim es per day. So, putting the number of satellites in a line formation thus forming a ring around earth, allows 28 to 30 detections per day. For example, all objects at e.g. 600 km altitude in a circular orbit need 96 min to complete one full orbit which is also called the orbital period time. This sums up to 15 orbits per day and therefore 30 times crossing the in-space detection fence per day. This improves the detection of objects in space, e.g. in terms of detection frequency, reliability, etc., and the determination of these objects' orbits. The satellite constellation, i.e. the in-space detection fence, allows for detecting, identifying, and characterizing of passive and active objects including space debris in the space domain. It further allows for orbit determination and prediction of orbits of objects. Further, the satellite constellation allows for cataloging of objects in an object catalog. It also allows for at least one of early warning, proximity alerting, collision between space objects warning, alerting and recording, maneuver detection, determining re-entry of space objects into the atmosphere, and fragmentation of space objects. In other words, the method is based on the finding that operating the number of satellites with detection device in a special formation constellation with in-space, i.e. on-board, processing circuitry provides a high- performance processing infrastructure to optimize several SSA-, SST-and SDA-KPIs.

[0013] As used herein, the at least one object in space to be detected may be at least one of an active object, e.g. an operational satellite or the like, and an inactive object, e.g. an abandoned rocket body, debris, etc. The at least one object may orbit around the planet, e.g. the earth, or natural satellite, e.g. the moon.

[0014] Further, as used herein, the satellite constellation may be understood as a group of artificial satellites, i.e. the number of satellites, working together as a system. The at least approximated line formation of the number of satellites may be understood that the number of satellites are arranged along a line that extends around the planet or natural satellite. The line formation may also be understood as e.g. an equatorial ring at a specific altitude band, through which every object with an orbit within this altitude band must pass twice per orbit. It is understood that deviations or an at least slight offset between individual satellites fall within the line formation, so that the line formation is at least approximated. The forming of the satellite constellation may comprise bringing each of the number of satellites into orbit, e.g. by launching a spacecraft, carrier rocket, or the like, that carries one or more of the number of satellites into space. Further, forming of the satellite constellation may comprise causing each of the number of satellites to perform an acceleration and / or deceleration process to reach a desired orbit.

[0015] In addition, as used herein, the detection device of the respective satellite of the number of satellites may be configured to detect objects based on at least one of radar, optical detection utilizing optical wavelengths reflected by objects, similar to astronomical telescopes, lidar, radio-frequency ranging, or the like.

[0016] Further, as used herein, the on-board processing circuitry coupled to the detection device may be a single dedicated processor, a single shared processor, or a plurality of individual processors, some of which or all of which may be shared, a digital signal processor (DSP) hardware, an application specific integrated circuit (ASIC), a neuromorphic processor or a field programmable gate array (FPGA), a general purpose processing unit (CPU), highly parallel or Machine Learning focused processors (GPUs, TPUs, or similar), or comparable circuitries. The processing circuitry may optionally be operatively connected to, e.g., read only memory (ROM) for storing software, random access memory (RAM) and / or nonvolatile memory. Further, it may comprise or may be coupled to a communication interface configured for communicating among the number of satellites and / or for communicating to ground, e.g. to a ground station located at the planet, e.g. the earth. The on-board processing circuitry may comprise or may be coupled to one or more of a hardware driver, a telemetric system, and a flight controller, which in turn may be coupled to a propulsion system of the respective satellite. The onboard processing circuitry may be configured to receive and process data provided by the detection device. Further, the processing circuitry may be configured to control the detection device. In addition, the processing circuitry may be configured to control flight of the respective satellite. For this purpose, the onboard processing circuitry may be configured to receive and / or process control data, e.g. comprising commands or the like to control movement and / or orientation of the satellite to form the satellite constellation. At least some of the functionalities of the processing circuitry may be implemented in software. For example, the satellite constellation and / or an individual or subset of the number of satellites may be operated to re-detect a known object, for tasking where the detection device is deliberately pointed towards some point of interest for some specific time, and / or for general surveillance where new, yet unknown or tracked, objects are to be detected.

[0017] According to an embodiment, the line formation may span, with respect to a field- of-view of the detection devices of the number of satellites in combination, an at least substantially closed ring around the planet or natural satellite. For example, the satellite constellation may form a ring at a specific altitude band, through which every object with an orbit within this altitude must pass twice per orbit.

[0018] Thereby, flying objects may be detected, re-identified, and / or quantified in various characteristics through detection, e.g. measurement and / or recognition. A distance between the satellites along the line formation, i.e. along the circumferential line or in the circumferential direction of the ring, may be selected and / or set to form an at least essentially closed ring.

[0019] In an embodiment, the number of satellites may orbit in one, particularly in a common, orbital plane and / or altitude band. Merely by way of example, with respect to the earth, the number of satellites may orbit in an altitude band of approx. 500 km to 1.100 km, wherein this is not limited herein. The orbital plane may be indicated by the altitude and an inclination angle.

[0020] According to an embodiment, the detection device of at least part of the number of satellites may be oriented towards space. This is to be seen in contrast to earth observation, where the satellite or its detection device would be aligned towards the earth. For example, the detection device may point in the opposite direction of NADIR and look at 0° or 180° in flight direction.

[0021] In an embodiment, each detection device and / or processing circuitry forms a node, and the number of satellites is operated as a collaborative system with a corresponding number of nodes. Accordingly, the satellite constellation may be seen as a collaborative computing system with compute nodes at each of the number of satellites and ground-based resources. Such an architecture provides a more robust overall design with respect to limitations in communication or full outages. Also, it allows for scalability. While ground based resources can be considered unlimited, space-based computer resources automatically scale with the number of detection device, i.e. additional satellites. In this way, each satellite and / or node may perform the task of object detection and orbit determination on its own. Combining numerous such nodes in a system, the overall swarm intelligence adds to accuracy, confidence, and robustness.

[0022] According to an embodiment, the number of satellites may communicate and / or exchange data with each other, either directly or indirectly via space-based or ground-based intermediary. For this purpose, the respective satellite may comprise at least one communication interface for in-space communications and / or communications from and / or to ground.

[0023] In an embodiment, an orbit of the one or more objects may be determined based on the monitoring of the space. Orbit determination in practice may presume a high number of detections, e.g. position detections, of a unique object in space. For example, this may require up to around 300 position detections of a unique object, wherein this number of position detections is merely exemplary. At object speeds > 7km / s a detection window may be too short for such high number of detections. Using the satellite constellation for detecting and / or monitoring and / or re-identifying objects in space allows for a higher number of detections within a time frame of the same duration. The above-mentioned 300 position detections may then be acquired within a few hours instead of within days, thereby allowing an at least more accurate orbit determination.

[0024] In an embodiment, the respective detection device may be controlled, by the corresponding processing circuitry of the respective satellite, to align to at least one specific point of interest for a specific time. This may also be referred to as the above-mentioned tasking. For example, the processing circuitry may be configured to control the detection device accordingly.

[0025] According to an embodiment, a respective satellite of the number of satellites may maintain or accesses a catalog of objects known in space. For example, one or more of the number of satellites may maintain the catalog. Satellites that do not maintain their own catalog, e.g. to save resources, may access a satellite with a catalog. The catalog may be stored in a memory or the like. The respective satellite may update the catalog upon detection, and an optional verification or the like, of a new object.

[0026] In an embodiment, the respective satellite may determine, by its processing circuitry, an orbit of at least one known object. For example, the orbit determined may be used to identify an object crossing the satellite's or detection device's field-of-view. According to an embodiment, the respective satellite may determine, by its processing circuitry, whether a known object will arrive and / or which known object will next arrive in the detection range of its detection device and controls its detection device accordingly. The next objects may also be managed in a queue.

[0027] In an embodiment, the respective satellite may determine, by its processing circuitry, a lead time prior to an expected time of encounter with a known object. The lead time may be used to trigger the detection device of the respective satellite accordingly. In other words, for re-detecting a known object, the processing circuitry may determine, e.g. select, a certain lead time prior to the expected time of intersection. This lead time may act as a buffer to not "miss" the objects. The lead time can be smaller the more accurate the current orbit of an object is deferred. From deducting this lead time from the expected time of crosspassing, a trigger time for the detection device is naturally given.

[0028] According to an embodiment, one or more of the number of satellites are controlled to detect and catalog objects not yet known. This may also be referred to as the above-mentioned general surveillance. For example, the respective satellite, e.g. its processing circuitry, may receive a corresponding request from another of the number of satellites and / or from a ground station.

[0029] In an embodiment, the respective satellite may autonomously detect and catalog a yet unknown object by its detection device and processing circuitry. Such an autonomous scheduling may result from e.g. an overall strategic optimization of resource usage in comparison to used resources, e.g. energy. According to an embodiment, one or more of the number of satellites may be controlled to re-identify and / or track an object already known. This may also be referred to as the above-mentioned tasking. For example, the respective satellite, e.g. its processing circuitry, may receive a corresponding request from another of the number of satellites and / or from a ground station.

[0030] In an embodiment, one or more of the number of satellites autonomously may redetect and / or re-identify an object already known and update a respective catalog. Such an autonomous scheduling may result from e.g. an overall strategic optimization of resource usage in comparison to used resources, e.g. energy.

[0031] According to an embodiment, one or more of the number of satellites may be controlled to determine at least one promising orbit in which a corresponding object is likely to be expected and to monitor the at least one promising orbit. This concentrates on monitoring a promising orbit rather than detecting random objects. For example, the at least one promising orbit may be determined based on knowledge about the earth orbital mechanics system. Once the at least one promising orbit is determined, the processing circuitry may control the detection device to continuously monitor the at least one promising orbit. For instance, the determination of the at least one promising orbit may utilize methods such as the Hough transform. The target space of this transformation represents certain parametrized geometric shapes, here elliptical orbits, where each axis represents one parameter of this shape. Observations in the origin space are then transformed in analogy to a voting mechanism, contributing and adding up to each point in the target space that represents a shape / orbit, this observation could originate from. Using a discrete representation of the target space will end up in a histogram-like representation, indicating clusters of orbits where many objects are likely to be present. This approach provides that the Hough transform may overcome the issue of inaccurate or partly missing data to some degree.

[0032] In an embodiment, the respective satellite may vary and / or adjust at least one detection and / or operating parameter of its detection device based on on-board scheduling and / or on-board tasking. For example, the processing circuitry may be configured to vary and / or adjust the detection device accordingly. The on-board scheduling and / or on-board tasking may depend on the operating mode of the respective satellite, such as the above-mentioned re-detection of a known object, the above-mentioned tasking where the detection device is deliberately pointed towards some point of interest for some specific time, and / or the above- mentioned general surveillance where new, yet unknown or tracked, objects are to be detected.

[0033] According to an embodiment, the respective satellite may vary and / or adjust at least one detection and / or operating parameter if an expected object cannot be detected within a detection signal of the respective detection device. This may affect only the respective satellite. In addition, this may also affect one or more other satellites of the number of satellites and / or the satellite constellation.

[0034] In an embodiment, the respective detection device and / or processing circuitry may be operated to allow several distinct detections. For example, this may comprise performing several detections at a same time, performing several detections in different directions, and / or performing several types of detections. This further increases the detection rate and / or detection quality. For instance, the detection device may be radar device having a number of individual radar fans that allow several distinct detections. According to an embodiment, the respective detection device and / or processing circuitry may be operated to track a bypassing object to derive at least one of a position vector and a velocity vector. The position vector and a velocity vector may be used for orbit determination and re-identification of an object, wherein knowledge about astrophysics and orbital dynamics may be additionally utilized.

[0035] In an embodiment, the detection device may be radar-based or may be formed as a radar detector. The detection device may comprise at least one of a transmitter, receiver, antenna, or a combination thereof. Optionally, the radar detector may comprise a number of radar fans, e.g. 1, 2, 3, 4 or more radar fans, which may also be referred to as radar visible planes. The detection device may be tilted in flight direction by about 30° (degrees). Further, the detection device may be oriented in 0° or 180° when considered in flight direction. When putting the radar on 90° degrees to flight direction, the velocities of objects are typically over 10 km / s. A continuous wave radar is then required to detect objects at this high speed. However, to always push the velocity down to under 10 km / s the radar may be turned to 0° or 180° (degrees) in flight direction. Instead of using a continuous wave radar with several drawbacks to position and velocity, a pulsed phased array may therefore be used. By way of example, the detection device may comprise a pulsed phased array radar. It may operate at approx. 7 GHz or less. Such operating frequency may allow to detect objects with 1 cm diameter assuming a spherical object.

[0036] According to an embodiment, the method may further comprise receiving, by a ground station, monitoring data comprising a result of the monitoring the space and / or at least one object detected during the monitoring from one or more of the number of satellites. The monitoring data may comprise at least one of a newly detected object, a re-identified and / or re-detected object, an updated catalog of known objects, or the like. In addition, monitoring data may be exchanged about the number of satellites.

[0037] In an embodiment, a data repository may be maintained on-ground. This may be made available to one or more of the number of satellites as required. The data repository may also be referred to as backup of on-board acquired and processed data in case of any damage to one of the number of satellites, loss of communication, or other failures. Also, when the number of satellites needs to recover after some failure or incident, its internal catalog, scheduler, and other components may be re-initialized from this global data repository.

[0038] According to an embodiment, the on-ground data repository may comprise at least one of a catalog of objects known in space and operating parameter data for one or more of the number of satellites. In this way, the data repository may be used as a backup for restoring data.

[0039] In embodiment, the planet is the Earth. The satellite constellation may be formed in any suitable orbit of the Earth. The satellite constellation may be launched and / or controlled from Earth. The number of satellites may also have stored and / or may also receive control data on the basis of which the satellite constellation may be formed after launching the number of satellites from Earth.

[0040] According to an embodiment, the satellite constellation may be formed in one of: low earth orbit (LEO), medium earth orbit (MEO), geostationary earth orbit (GEO), high earth orbit (HEO), and one or more orbits between the aforementioned. According to a further aspect, there is provided a system for detecting objects in space. The system comprises a satellite constellation comprising a number of satellites orbiting around a planet or natural satellite in a line formation, each of the number of satellites comprising a detection device and on-board processing circuitry coupled to the detection device. The satellite constellation is configured to monitor the space using the respective detection device and on-board processing circuitry of at least part of the number of satellites to detect one or more objects in space.

[0041] The system may be configured to carry out the method of the first aspect and may therefore be modified in accordance with any one of the above embodiments.

[0042] The system may also be configured to form the satellite constellation. For this purpose, the system may comprise or may utilize satellite launching means configured to launch the number of satellites, either individually or several at the same time, e.g. from the ground, e.g. from the Earth. The launching means may comprise at least one of a carrier rocket, spacecraft, or other means by which satellites may be launched into orbit. The system may be configured, e.g. by suitable processing circuitry, interface circuitry, etc., to cause each of the number of satellites to maneuver to a desired orbit in which the satellite constellation is to be formed. For example, the on-board processing circuitry of each satellite may receive or may be programmed based on control data configured to cause the satellite to move into the desired orbit and / or to form the satellite constellation, for example by using, e.g. controlling, etc., an on-board propulsion system. The control data may further be configured to cause the satellite to move to a certain altitude and an inclination angle. The system may cause all of the number of satellites to orbit in the same orbital plane and / or altitude band, for example by using, e.g. controlling, etc., an on-board propulsion system.

[0043] According to an embodiment, the system may further comprise a ground station communicatively coupled to at least one satellite of the satellite constellation. The ground station and the at least one satellite may be configured to communicate and / or exchange data with each other.

[0044] In an embodiment, each satellite may form a node, and the number of satellites is operated as a collaborative system with a corresponding number of nodes to track objects over a period of time and / or perform general surveillance of the space.

[0045] According to an embodiment, the system may further comprise a ground station communicatively coupled to the satellite.

[0046] According to a further aspect, there is provided a satellite for detecting objects in space. The satellite is configured to orbit around a planet or natural satellite. The satellite comprises a detection device oriented towards space and on-board processing circuitry coupled to the detection device. The detection device and onboard processing circuitry are configured to detect one or more objects in space. The satellite is configured to form part of a constellation of a number of such satellites in an approximated line formation.

[0047] In an embodiment, a field-of-view configuration of the detection device may be selected and / or controlled to form, in combination with the other satellites of the constellation, an at least substantially closed ring around the planet or natural satellite. According to an embodiment, the detection device may be radar-based or is formed as a radar detector. The detection device may comprise a number of radar fans, e.g. 2, 3, 4 or more radar fans, which may also be referred to as radar visible planes. The detection device may be tilted in flight direction by about 30° (degrees), wherein tilt angles of at least 20° are also conceivable. Further, the detection device may be oriented in 0° or 180° when considered in flight direction. When putting the radar on 90° degrees to flight direction, the velocities of objects are typically over 10 km / s. A continuous wave radar is then required to detect objects at this high speed. However, to always push the velocity down to under 10 km / s the radar may be turned to 0° or 180° (degrees) in flight direction. Instead of using a continuous wave radar with several drawbacks to position and velocity, a pulsed phased array may therefore be used. By way of example, the detection device may comprise a pulsed phased array radar. It may operate at approx. 7 GHz or less. Such operating frequency may allow to detect objects with 1 cm diameter assuming a spherical object.

[0048] A further aspect relates to the use of a satellite constellation comprising a number of satellites orbiting around a planet or natural satellite in a line formation, wherein each of the number of satellites comprises a detection device and on-board processing circuitry coupled to the detection device, for determining an orbit of at least one object in space. Alternatively or additionally, the system and / or the satellite described herein may be used for orbit determination of at least one object in space. Orbit determination in practice may presume a high number of detections, e.g. position detections, of a unique object in space. For example, this may require up to around 300 position detections of a unique object. At object speeds > 7km / s a detection window may be too short for such high number of detections. Using the satellite constellation for detecting and / or monitoring and / or re-identifying objects in space allows for a higher number of detections within a time frame of the same duration. The above-mentioned 300 position detections may then be acquired within a few hours instead of within days, thereby allowing an at least more accurate orbit determination.

[0049] In a further aspect, there is provided a non-transitory machine-readable medium having stored thereon a (computer) program having a program code for performing the method according to the first aspect, when the program is executed on a processor or a programmable hardware. Examples may also cover program storage devices, such as digital data storage media, which are machine-, processor- or computer-readable and encode and / or contain machine-executable, processor-executable or computer-executable programs and instructions. Program storage devices may include or be digital storage devices, magnetic storage media such as magnetic disks and magnetic tapes, hard disk drives, or optically readable digital data storage media, for example. Other examples may also include computers, processors, control units, (field) programmable logic arrays ((F)PLAs), (F)PGA), graphics processor units (GPU), ASICs, integrated circuits (ICs) or system- on-a-chip (SoCs) systems programmed to execute the steps of the methods described herein.

[0050] In a further aspect, there is provided a (computer) program having a program code for performing the method according to the first aspect, when the program is executed on a processor or a programmable hardware. Thus, steps, operations or processes of different ones of the methods described above may also be executed by programmed computers, processors or other programmable hardware components. BRIEF SUMMARY OF THE DRAWINGS

[0051] The present invention is explained in more detail below with reference to the embodiments shown in the schematic figures:

[0052] Fig. 1 illustrates an exemplary system for detecting objects in space according to an embodiment.

[0053] Fig. 2 illustrates an exemplary system for detecting objects in space according to an embodiment.

[0054] Fig. 3 illustrates an exemplary system for detecting objects in space according to an embodiment.

[0055] Fig. 4 illustrates in a block diagram a satellite for detecting objects in space according to an embodiment.

[0056] Fig. 5 illustrates in a flowchart a method for detecting objects in space according to an embodiment.

[0057] In the figures of the drawing, elements, features, and components which are identical, functionally identical and of identical action are denoted in each case by the same reference designations unless stated otherwise.

[0058] DESCRIPTION OF EXEMPLARY EMBODIMENTS Fig. 1 illustrates an exemplary system for detecting objects in space. Such object, generally denoted by reference sign 12, may be at least one of an active object, e.g. an operational satellite or the like, and an inactive object, e.g. an abandoned rocket body, debris, etc. The at least one object 12 may orbit around a planet 14, e.g. the earth, or natural satellite, e.g. the moon. There are several orbits 16 around the planet 14, one of which is exemplarily illustrated in Fig. 1. For example, the orbit may be one of low earth orbit (LEO), medium earth orbit (MEO), geostationary earth orbit (GEO), high earth orbit (HEO), and one or more orbits between the aforementioned.

[0059] The system comprises a satellite constellation 100 comprising a number of satellites 110 orbiting around the planet 14 or natural satellite in a line formation. The number of satellites is in the exemplary orbit 16. Further, each of the number of satellites 110 comprises a detection device 112 and on-board processing circuitry 114 coupled to the detection device 112.

[0060] The satellite constellation 100 is configured to monitor the space using the respective detection device 112 and on-board processing circuitry 114 of at least part of the number of satellites 110 to detect one or more objects 12 in space.

[0061] The detection device 112 of the respective satellite of the number of satellites 110 may be configured to detect objects, such as object 12, based on at least one of radar, optical detection utilizing optical wavelengths reflected by objects, similar to astronomical telescopes, lidar and radio-frequency ranging. In this exemplary embodiment, the respective detection device 112 is radar-based or formed as a radar detector. The respective detection device 112 may comprise a number of radar fans, e.g. 2, 3, 4 or more radar fans, which may also be referred to as radar visible planes. The detection device 112 may be tilted in flight direction by about 30° (degrees), wherein tilt angles of at least 20° are also conceivable. Further, the detection device 112 may be oriented in 0° or 180° when considered in flight direction. By way of example, the detection device 112 may comprise a pulsed phased array radar. It may operate at approx. 7 GHz or less.

[0062] The on-board processing circuitry coupled to the detection device may be a single dedicated processor, a single shared processor, or a plurality of individual processors, some of which or all of which may be shared, a digital signal processor (DSP) hardware, an application specific integrated circuit (ASIC), a neuromorphic processor or a field programmable gate array (FPGA). The processing circuitry may optionally be operatively connected to, e.g., read only memory (ROM) for storing software, random access memory (RAM) and / or non-volatile memory. Further, it may comprise or may be coupled to a communication interface configured for communicating among the number of satellites and / or for communicating to ground, e.g. to a ground station located at the planet, e.g. the earth. The on-board processing circuitry 114 may comprise or may be coupled to one or more of a hardware driver, a telemetric system, and a flight controller, which in turn may be coupled to a propulsion system of the respective satellite. The on-board processing circuitry 114 may be configured to receive and process data provided by the detection device. Further, the processing circuitry 114 may be configured to control the detection device 112. In addition, the processing circuitry 114 may be configured to control flight of the respective satellite. For this purpose, the onboard processing circuitry 114 may be configured to receive, store and / or process control data, e.g. comprising commands or the like, to control movement and / or orientation of the satellite to form the satellite constellation 100. At least some of the functionalities of the processing circuitry may be implemented in software. In at least some embodiments, the number of satellites 110 may communicate and / or exchange data with each other, either directly or indirectly via space-based or ground-based intermediary. For this purpose, the respective satellite may comprise at least one communication interface for in-space communications and / or communications from and / or to ground. The at least one communication interface may be coupled to the detection device 112 and / or the on-board processing circuitry 114.

[0063] The system may be configured, e.g. by suitable processing and / or control circuitry, interface circuitry, etc., to control and / or cause each of the number of satellites 110 to maneuver to a desired orbit in which the satellite constellation 100 is to be formed. For example, the on-board processing circuitry 114 of each satellite may receive or may be programmed based on control data configured to cause the satellite to move and / or maneuver into the desired orbit, e.g. orbit 16, and / or to form the satellite constellation 100, for example by using, e.g. controlling, etc., an on-board propulsion system of the respective satellite. The control data may further be configured to cause the respective satellite to move and / or maneuver to a certain altitude and an inclination angle. The system may cause all of the number of satellites 110 to orbit in the same orbital plane and / or altitude band, for example by using, e.g. controlling, etc., an on-board propulsion system.

[0064] In at least some embodiments, the line formation may span, with respect to a field- of-view of the detection devices 112 of the number of satellites 110 in combination, an at least substantially closed ring around the planet 14 or natural satellite. In Fig. 1, dashed lines 116 exemplarily illustrate such field-of-view and / or detection range of the detection devices 112. For example, the satellite constellation 100 may form an equatorial ring at a specific altitude band, through which every object, e.g. object 12, with an orbit, e.g. orbit 16, within this altitude must pass twice per orbit. Thereby, flying objects, e.g. object 12, may be detected, re-identified, and / or quantified in various characteristics through detection, e.g. measurement and / or recognition. A distance between the satellites 110 along the line formation, i.e. along the circumferential line or in the circumferential direction of the ring, may be selected and / or set to form an at least essentially closed ring. The number of satellites 110 may orbit in one, particularly in a common, orbital plane and / or altitude band. Merely by way of example, with respect to the earth, the number of satellites may orbit in an altitude band of approx. 500 km to

[0065] 1.100 km, wherein this is not limited herein. The orbital plane may be indicated by the altitude and an inclination angle.

[0066] In at least some embodiments, the respective detection device 112 of at least part of the number of satellites 110 may be oriented towards space. This is to be seen in contrast to earth observation, where the satellite or its detection device would be aligned towards the earth. For example, the detection device 114 may point in the opposite direction of NADIR and look at 0° or 180° in flight direction.

[0067] Each detection device 112 and / or processing circuitry 114 may form a node, and the number of satellites 110 is operated as a collaborative system with a corresponding number of nodes. Accordingly, the satellite constellation 100 may be seen as a collaborative computing system with compute nodes at each of the number of satellites 110 and, at least optionally, ground-based resources.

[0068] In at least some embodiments, the respective detection device 112 may be controlled, by the corresponding on-bord processing circuitry 114 of the respective satellite, to align to at least one specific point of interest for a specific time. This may also be referred to as tasking. For example, the processing circuitry 114 may be configured to control the detection device 112 accordingly.

[0069] Further, in at least some embodiments, a respective satellite of the number of satellites 110 may maintain or accesses a catalog of objects known in space. For example, one or more of the number of satellites 110 may maintain the catalog. Satellites that do not maintain their own catalog, e.g. to save resources, may access a satellite with a catalog. The catalog may be stored in a memory or the like. The respective satellite may update the catalog upon detection, and an optional verification or the like, of a new object, e.g. object 12.

[0070] In at least some embodiments, the respective satellite may determine, by its processing circuitry 114, an orbit of at least one known object, e.g. of object 12. For example, the orbit determined may be used to identify an object, e.g. object 12, crossing the satellite's or detection device's field-of-view. For example, an orbit is an ellipse and determined by six parameters. Two parameters define the shape and size of the ellipse. Parameter a - the semi-major axis - is the sum of the periapsis and apoapsis distances divided by two. For classic two-body orbits, the semi-major axis is the distance between the centers of the bodies, not the distance of the bodies from the center of mass. Parameter e - the eccentricity - is the shape of the ellipse, describing how much it is elongated compared to a circle. Two parameters define the orientation of the orbital plane in which the ellipse is embedded. Parameter i is the inclination, parameter Q is the right ascension of the ascending node. Parameter w is the argument of the perigee. Parameter v is the true anomaly. Parameter M = coO(t - tO) is the mean anomaly. The SGP4 algorithm is an analytical orbit propagation algorithm. Given the Keplerian orbital parameters the SGP4 algorithm analytically gives position- and velocity-vectors for a list of time steps. Given a list of at least 3 position- and velocity-vectors e.g. the Gibb's method allows an Initial Orbit Determination - IOD - without an initial guess. In general, an IOD is also possible with a single pair of position and velocity vector. Further, in at least some embodiments, the respective detection device 112 and / or processing circuitry 114 may be operated to track a bypassing object, e.g. object 12, to derive at least one of a position vector and a velocity vector at one or more time steps. The position vector(s) and a velocity vector(s) may be used for orbit determination and re-identification of an object, wherein knowledge about astrophysics and orbital dynamics may be additionally utilized.

[0071] In at least some embodiments, the respective satellite may determine, by its processing circuitry 114, whether a known object will arrive and / or which known object will next arrive in the detection range of its detection device 112 and controls its detection device 112 accordingly. The next objects may also be managed in a queue. Optionally, the respective satellite may determine, by its processing circuitry 114, a lead time prior to an expected time of encounter with a known object. The lead time may be used to trigger the detection device 112 of the respective satellite accordingly. In other words, for re-detecting a known object, the processing circuitry 114 may determine, e.g. select, a certain lead time prior to the expected time of intersection. This lead time may act as a buffer to not "miss" the objects. The lead time can be smaller the more accurate the current orbit of an object is deferred. From deducting this lead time from the expected time of cross-passing, a trigger time for the detection device 112 is naturally given.

[0072] According to an embodiment, one or more of the number of satellites 110 are controlled to detect and catalog objects, e.g. object 12, not yet known. This may also be referred to as the above-mentioned general surveillance. For example, the respective satellite, e.g. its processing circuitry 114, may receive a corresponding request for surveillance from another one of the number of satellites 110 and / or from a ground station. Additionally or alternatively, the respective satellite may autonomously detect and catalog a yet unknown object, e.g. object 12, by its detection device and processing circuitry 114. Such an autonomous scheduling may result from e.g. an overall strategic optimization of re-source usage in comparison to used resources, e.g. energy.

[0073] Further, in at least some embodiments, one or more of the number of satellites 110 may be controlled to re-identify and / or track an object already known. This may also be referred to as the above-mentioned tasking. For example, the respective satellite, e.g. its processing circuitry 114, may receive a corresponding request from another of the number of satellites and / or from a ground station. Additionally or alternatively, one or more of the number of satellites 110 may autonomously re-detect and / or re-identify an object already known and update a respective cata-log. Such an autonomous scheduling may result from e.g. an overall strategic optimization of resource usage in comparison to used resources, e.g. energy.

[0074] In at least some embodiments, one or more of the number of satellites 110 may be controlled to determine at least one promising orbit in which a corresponding object is likely to be expected and to monitor the at least one promising orbit. This concentrates on monitoring a promising orbit rather than detecting random objects. For example, the at least one promising orbit may be determined based on knowledge about the earth orbital mechanics system. Once the at least one promising orbit is determined, the processing circuitry 114 may control the detection device 112 to continuously monitor the at least one promising orbit. For instance, the determination of the at least one promising orbit may utilize Hough transform. The target space of this transformation represents certain parametrized geometric shapes, here elliptical orbits, where each axis represents one parameter of this shape. Observations in the origin space are then transformed in analogy to a voting mechanism, contributing and adding up to each point in the target space that represents a shape I orbit, this observation could originate from. Using a discrete representation of the target space will end up in a histogram-like representation, indicating clusters of orbits where many objects are likely to be present. This approach provides that a method such as the Hough transform may overcome the issue of inaccurate or partly missing data to some degree.

[0075] Further, in at least some embodiments, the respective satellite may vary and / or adjust at least one detection and / or operating parameter of its detection device 112 based on on-board scheduling and / or on-board tasking. For example, the processing circuitry 114 may be configured to vary and / or adjust the detection device 112 accordingly. The on-board scheduling and / or on-board tasking may depend on the operating mode of the respective satellite, such as re-detection of a known object, tasking where the detection device 112 is deliberately pointed towards some point of interest for some specific time, and / or the above- mentioned general surveillance where new, yet unknown or tracked, objects are to be detected.

[0076] Also, in at least some embodiments, the respective satellite may vary and / or adjust at least one detection and / or operating parameter if an expected object cannot be detected within a detection signal of the respective detection device 112. This may affect only the respective satellite. In addition, this may also affect one or more other satellites of the number of satellites 110 and / or the satellite constellation 100.

[0077] In at least some embodiments, the respective detection device 112 and / or processing circuitry 114 may be operated to allow several distinct detections. For example, this may comprise performing several detections at a same time, performing several detections in different directions, and / or performing several types of detections. For instance, the detection device 112 may be radar device having a number of individual radar fans or a respective field-of-view that allow several distinct detections.

[0078] Fig. 2 illustrates the exemplary system for detecting objects in space in another way. Again, the satellite constellation 100 comprising the number of satellites 110, only one of which is illustrated in Fig. 1 for a better overview, orbits in the orbit 16 around the planet 14. As indicated by the field-of-view and / or detection range 116 formed by the number of satellites 110 orbiting in line formation, an in-space detection fence may be formed by the satellite constellation. As illustrated in Fig. 2, the object 12 crosses the field-of-view and / or detection range 116, i.e. the in-space detection fence, twice per orbit, as also indicated by arrow A.

[0079] Further, in Fig. 2, reference sign S indicates a side view of the respective satellite of the number of satellites 110. Reference sign F indicates a front view of the respective satellite of the number of satellites 110. Reference sign D indicates a direction of flight of the individual satellite and / or the number of satellites 110.

[0080] The respective detection device 112 comprises one or more radar wings and / or radar fans 112A allowing for multiple detections at a single by-pass of the object 12, wherein the illustrated number of three such radar wings and / or radar fans is merely exemplary, and less or more radar wings and / or radar fans are conceivable. The number of radar wings and / or radar fans 112A may be adjustable, and may be controllable, e.g. via the processing circuitry 114. Reference sign 112B indicates a direction of view of the detection device 112 and / or the number of radar wings and / or radar fans 112A.

[0081] Fig. 3 illustrates the exemplary system for detecting objects in space in yet another way. Accordingly, the system may further comprise a ground-station 120 located on the planet 14, e.g. the Earth. The ground-station 120 and at least one of the number of satellites 110 are configured to communicate with each other. For example, the ground-station 120 may be configured to provide, e.g. transmit, data, e.g. control data, request data, configuration data, backup and / or restoration data, or the like, to the at least one of the number of satellites 110. Data may be provided to each satellite individually or may be provided to one of the number of satellites 110, from where the data may be distributed among the number of satellites 110.

[0082] The system may also be configured to form the satellite constellation 100. For this purpose, the system may comprise or may utilize satellite launching means configured to launch the number of satellites 110, either individually or several at the same time, e.g. from the ground, e.g. from the Earth. The launching means may comprise at least one of a carrier rocket, spacecraft, or other means by which satellites may be launched into orbit. The system may be configured, e.g. by suitable processing circuitry, interface circuitry, etc., to cause each of the number of satellites 110 to maneuver to a desired orbit, e.g. orbit 16, in which the satellite constellation 100 is to be formed. For example, the on-board processing circuitry 114 of each satellite may receive or may be programmed based on control data configured to cause the satellite to move and / or maneuver into the desired orbit and / or to form the satellite constellation, for example by using, e.g. controlling, etc., an on-board propulsion system. The control data may further be configured to cause the satellite to move to a certain altitude and an inclination angle. The system may cause all of the number of satellites 110 to orbit in the same orbital plane and / or altitude band, for example by using, e.g. controlling, etc., an onboard propulsion system.

[0083] In at least some embodiments, the ground station 120 may be configured to receive monitoring data comprising a result of the monitoring of the space and / or at least one object, e.g. object 12, detected during the monitoring from one or more of the number of satellites 110. The monitoring data may comprise at least one of a newly detected object, a re-identified and / or re-detected object, an updated catalog of known objects, or the like. In addition, monitoring data may be exchanged about the number of satellites 110.

[0084] Further, in at least some embodiments, a data repository may be maintained on- ground, e.g. by the ground-station 120. This may be made available to one or more of the number of satellites 110 as required. The data repository may also be referred to as backup of on-board acquired and processed data in case of any damage to one of the number of satellites 110, loss of communication, or other failures. Also, when the number of satellites needs to recover after some failure or incident, its internal catalog, scheduler, and other components may be reinitialized from this global data repository. Further, the on-ground data repository may comprise at least one of a catalog of objects known in space and operating parameter data for one or more of the number of satellites. In this way, the data repository may be used as a backup for restoring data.

[0085] Fig. 4 illustrates in a block diagram a satellite for detecting objects in space, i.e. one exemplary one of the number of satellites 110.

[0086] In addition to the detection means 112 and the on-board processing circuitry 114, each satellite of the number of satellites 110 may further comprise at least one of an on-board propulsion system 117, an energy supply 118, and at least one communication interface 119. At least some of these components may be operatively coupled to each other. For example, the processing circuitry 114 may be configured to interact with at least one of the propulsion system 117, energy supply 118, and the at least one communication interface 119 to control operation of the satellite.

[0087] Further, in at least some embodiments, the processing circuitry 114 may comprise or may execute an on-board scheduler. For example, the on-board scheduler may have access to a representation of the maintained catalog of known objects. It may also comprise means to compute orbits of these objects and identify those objects which will cross the satellite's radar beam next. These next objects may be managed in a queue. For re-detecting a known object, the scheduler may select a certain lead time prior to the expected time of intersection. This lead time acts as a buffer to not "miss" the objects and can be smaller the more accurate the current orbit of an object is deferred. From deducting this lead time from the expected time of cross-passing, a trigger time for the radar is naturally given. A second type of event, the scheduler can manage refers to tasking. This is when a radar is deliberately pointed towards some point of interest at and for some specific time. Those events can be directly queued by the scheduler, according to a sent specification. A special case of tasking is general surveillance, where we aim at detecting new, yet unknown or tracked, objects. Those are also directly queued by the scheduler, according to a sent specification or autonomously. Such an autonomous scheduling results from an overall strategic optimization of resource usage in comparison to used resources (e.g. energy).

[0088] Further, in at least some embodiments, the processing circuitry 114 may comprise or may execute an on-board radar controller. For example, it may be configured to controls the radar at one single satellite, according to its scheduler. It may act as an abstraction layer between the scheduler and the actual (radar) sensor, to allow for interchangeability of different sensor types or interfaces (manufacturers). It also performs condition monitoring, observing if the radar performs as commanded and retrieved results as well as health parameters are plausible. The radar control processor can also autonomously vary radar parameters in coordination with the detection and verification processor in a scenario where an expected object cannot be detected within the radar signal.

[0089] In at least some embodiments, the processing circuitry 114 may comprise or may execute an on-board detection and verification controller. For example, this may be configured to process and evaluate radar raw data on-board on each satellite individually. The detection and verification processor may receive a stream of e.g. radar measurements and may perform data cleaning, filtering, and / or signal processing such that (potential) detections of objects are extracted and additional attributes such as speed and direction are inferred. In a subsequent verification step, the plausibility of a detection is checked based upon the radar measurements as well as known context (e.g. knowledge about an object to be detected). In at least some embodiments, the processing circuitry 114 may comprise or may execute an on-board re-identification controller. For example, it may be configured for re-identification, which is the task of either assigning a radar detection to a known object or recognizing it as a new, yet unknown object. There will be obvious scenarios, e.g. when an expected by-pass of a known object is indeed visible in the radar data, without any other detection close enough in time and space such that there is the risk of mixing them up. However, ambiguous scenarios may also be expected, where re-identification cannot be done at a high enough confidence, such that correlation with historic data as well as future observations is needed. Such detections are managed in an own database which is synchronized across all satellites.

[0090] Further, in at least some embodiments, the processing circuitry 114 may comprise or may execute an on-board / on-ground orbit determination controller. For example, it may be configured for orbit determination, which is a task that is done both - on-board as well as on-ground. Reason for this redundancy may be that two different purposes are served. On-board processing of orbits, i.e. refinement of predicted orbits taking a latest detection into account, is done to have highly accurate orbit predictions at the lowest possible latency. This allows it to hand over this information to other satellites or assets and their operators in case of close encounters. So, operators as well as autonomous systems receive latest updates to assess collision risks every half of an orbit. In scenarios where satellite to satellite communication is available, this can even be done independent from any ground infrastructure with their inherent constraints. The other purpose that is served is to maintain a global catalog of all tracked objects. From a software perspective, it is reasonable to also do this in a data center. Aspects accounted for simplicity provide managed access to such data, unlimited scalability of resources or availability. Also, the available compute resources allow for continued reprocessing of the global historical data to improve Machine Learning models for orbit determination in addition to engineered physical models or detect anomalies that might give reason to reconsider past decisions.

[0091] Further, in at least some embodiments, the system may be configured for onboard and / or on-ground detection and evaluation of unknown objects. For example, in case of unlimited energy and power budget the radar fence is "always on", allowing continuous detection, re-identification and cataloging of to date unknown or unidentified objects. But e.g. radar availability is limited due to energy, power, use for other either revenue generating or short-term more important use cases or outages. A strategy 1) to detect and 2) to re-identify to date unknown or unidentified objects is to apply a set of processors specialized on different tasks and an explicit astrophysics and orbital dynamics knowledge. This strategy aims at optimizing the chance of orbit determination and re-identification with the only use of position and velocity-vectors. The naive, brute force strategy is to switch each radar on as long as energy and power can be supplied by a smart on-board battery management system for recharging and over the mission lifetime. While this strategy comes up with multiple detections, orbit determination and continued re-identification is unlikely. In a more efficient approach, it is not concentrated on detecting random objects but rather to identify promising orbits (POs). It may consider explicit knowledge of the Earth's orbital mechanics system. Once a PO is selected, a processor controls the continuous monitoring of the promising orbit.

[0092] Further, in at least some embodiments, the system may comprise a data pipeline. Fig. 5 illustrates in a flow chart a method 500 for detecting objects in space. The method comprises forming 510 a satellite constellation comprising a number of satellites orbiting around a planet or natural satellite in an at least approximated line formation, each of the number of satellites comprising a detection device oriented towards space and on-board processing circuitry coupled to the detection device. The method further comprises monitoring 520 of the space using the respective detection device and on-board processing circuitry of at least part of the number of satellites to detect one or more objects in space.

[0093] LIST OF REFERENCE SIGNS

[0094] 12 object

[0095] 14 planet, e.g. Earth 16 orbit

[0096] 100 satellite constellation

[0097] 1 10 number of satellites

[0098] 1 12 detection device

[0099] 1 12A radar wing / radar fan 112B direction of view

[0100] 1 14 processing circuitry

[0101] 1 16 field-of-view and / or detection range

[0102] 1 17 propulsion system

[0103] 1 18 energy supply 1 19 communication interface

[0104] 120 ground-station

Claims

PATENT CLAIMS1. A method (500) for detecting objects (12) in space, the method comprising: forming (510) a satellite constellation (100) comprising a number of satellites (110) orbiting around a planet (14) or natural satellite in an at least approximated line formation, each of the number of satellites (110) comprising a detection device (112) and on-board processing circuitry (114) coupled to the detection device; and monitoring (520) of the space using the respective detection device (112) and on-board processing circuitry (114) of at least part of the number of satellites (110) to detect one or more objects in space.

2. The method of claim 1, wherein the line formation spans, with respect to a field-of-view (116) of the detection devices (112) of the number of satellites (110) in combination, an at least substantially closed ring around the planet (14) or natural satellite.

3. The method of claim 1 or 2, wherein the number of satellites (110) orbit in one, particularly in a common, orbital plane and / or altitude band.

4. The method of any one of the preceding claims, wherein the detection device (112) of at least part of the number of satellites (110) is oriented towards space.

5. The method of any one of the preceding claims, wherein each detection device (112) and / or processing circuitry (114) forms a node, and the numberof satellites (110) is operated as a collaborative system with a corresponding number of nodes.

6. The method of any one of the preceding claims, wherein the number of satellites (110) communicate and / or exchange data with each other, either directly or indirectly via space- or ground-based intermediary.

7. The method of any one of the preceding claims, further comprising: determining an orbit of the one or more objects (12) based on the monitoring of the space.

8. The method of any one of the preceding claims, wherein the respective detection device (112) is controlled, by the corresponding processing circuitry of the respective satellite, to align to at least one specific point of interest for a specific time.

9. The method of any one of the preceding claims, wherein a respective satellite of the number of satellites (110) maintains or accesses a catalog of objects known in space.

10. The method of claim 9, wherein the respective satellite determines, by its processing circuitry (114), an orbit of at least one known object.

11. The method of claim 9 or 10, wherein the respective satellite determines, by its processing circuitry (114), whether a known object will arrive and / or which known object will next arrive in the detection range (116) of its detection device and controls its detection device (112) accordingly.

12. The method of any one of claims 9 to 11, wherein the respective satellite determines, by its processing circuitry (114), a lead time prior to an expected time of encounter with a known object, and the lead time is used to trigger the detection device of the respective satellite accordingly.

13. The method of any one of the preceding claims, wherein one or more of the number of satellites (110) are controlled to detect and catalog objects not yet known.

14. The method of any one of the preceding claims, wherein the respective satellite autonomously detects and catalogs a yet unknown object by its detection device (112) and processing circuitry (114).

15. The method of any one of the preceding claims, wherein one or more of the number of satellites (110) are controlled to re-identify and / or track an object already known.

16. The method of any one of the preceding claims, wherein one or more of the number of satellites (110) autonomously re-detect objects already known and update a respective catalog.

17. The method of any one of the preceding claims, wherein one or more of the number of satellites (110) are controlled to determine at least one promising orbit in which a corresponding object is likely to be expected and to monitor the at least one promising orbit.

18. The method of any one of the preceding claims, wherein the respective satellite varies and / or adjusts at least one detection and / or operating parameter of its detection device (112) based on on-board scheduling and / or on-board tasking.

19. The method of any one of the preceding claims, wherein the respective satellite varies and / or adjusts at least one detection and / or operating parameter if an expected object cannot be detected within a detection signal of the respective detection device (112).

20. The method of any one of the preceding claims, wherein the respective detection device (112) and / or processing circuitry (114) is operated to allow several distinct detections.

21. The method of any one of the preceding claims, wherein the respective detection device (112) and / or processing circuitry (114) is operated to track a bypassing object to derive at least one of a position vector and a velocity vector.

22. The method of any one of the preceding claims, wherein the detection device is radar-based or is formed as a radar detector.

23. The method of any one of the preceding claims, further comprising: receiving, by a ground station (120), monitoring data comprising a result of the monitoring the space and / or at least one object detected during the monitoring from one or more of the number of satellites (110).

24. The method of any one of the preceding claims, wherein a data repository is maintained on-ground and made available to one or more of the number of satellites as required.

25. The method of claim 24, wherein the on-ground data repository comprises at least one of a catalog of objects known in space and operating parameter data for one or more of the number of satellites.

26. The method of any one of the preceding claims, wherein the planet (14) is the Earth.

27. The method of any one of the preceding claims, wherein the satellite constellation (100) is formed in one of: low earth orbit, LEO, medium earth orbit, MEO, geostationary earth orbit, GEO,, high earth orbit, HEO, and one or more orbits between the aforementioned.

28. A system for detecting objects (12) in space, comprising: a satellite constellation (100) comprising a number of satellites (110) orbiting around a planet or natural satellite in a line formation, each of the number of satellites (110) comprising a detection device (112) and on-board processing circuitry (114) coupled to the detection device (112); wherein the satellite constellation (100) is configured to monitor the space using the respective detection device (112) and on-board processing circuitry (114) of at least part of the number of satellites (110) to detect one or more objects (12) in space.

29. The system of claim 28, further comprising a ground station communicatively coupled to at least one satellite of the satellite constellation (100).

30. The system of claim 28 or 29, wherein the detection device (112) is radarbased or is formed as a radar detector.

31. The system of any one of the claims 28 to 30, wherein each satellite forms a node, and the number of satellites (110) is operated as a collaborative system with a corresponding number of nodes to track objects over a period of time or perform general surveillance of the space.

32. The system of any of claim 28 to 31, further comprising a ground-station (120) communicatively coupled to the satellite.

33. A satellite (110) for detecting objects in space, the satellite being configured to orbit around a planet or natural satellite, the satellite comprising: a detection device (112) oriented towards space and on-board processing circuitry (114) coupled to the detection device; wherein the detection device and on-board processing circuitry (114) are configured to detect one or more objects in space; and wherein the satellite is configured to form part of a constellation (100) of a number of such satellites in an approximated line formation.

34. The satellite of claim 33, wherein the field-of-view configuration of the detection device (112) is chosen to form, in combination with the othersatellites of the constellation, an at least substantially closed ring around the planet or natural satellite.

35. The satellite of claim 33 or 34, wherein the detection device (112) is radarbased or is formed as a radar detector.

36. The use of a satellite constellation (100) comprising a number of satellites (110) orbiting around a planet or natural satellite in a line formation, each of the number of satellites (110) comprising a detection device (112) and onboard processing circuitry (114) coupled to the detection device (112), for determining an orbit of at least one object (12) in space.

37. A non-transitory machine-readable medium having stored thereon a program having a program code for performing the method according to any one of claims 1 to 27, when the program is executed on a processor or a programmable hardware.

38. A computer program having a program code for performing the method according to any one of claims 1 to 27, when the program is executed on a processor or a programmable hardware.

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