System and method for multi-frequency and multi-polarization scanning synthetic aperture radar modes at very coarse resolution

Abstract

Provided herein are systems and methods for beam mode design for multi-frequency, multi-polarization, and multi-frequency and multi-polarization ScanSAR at very coarse resolution. A method performed with a beam mode design application includes: receiving mission-specific beam mode design parameters; selecting a subset of beam mode configurations from a beam mode configuration space, wherein: (i) when the ratio of azimuth dwell time to pulse two-way return time is <1, the subset includes configurations that disregard pulse transmission window timing constraints, and (ii) when the ratio of azimuth dwell time to pulse two-way return time is <1 / 2, the subset includes configurations that allow two or more bursts transmission intervals to occur consecutively without intervening burst receive intervals; characterizing, a possible synthetic aperture radar (SAR) performance; generating outputs defining a possible beam mode; iteratively feeding back the outputs as inputs for further characterizing possible SAR performances; and outputting a compliant beam mode.

Description

SYSTEM AND METHOD FOR MULTI-FREQUENCY AND MULTI-POLARIZATION SCANNING SYNTHETIC APERTURE RADAR MODES AT VERY COARSE RESOLUTIONTechnical Field

[0001] The following relates generally to ScanSAR modes for generating wide swath imagery, and more particularly to systems and methods for achieving multifrequency and / or multi-polarization ScanSAR.Introduction

[0002] Scanning synthetic aperture radar mode, or “ScanSAR,” is commonly used by spaceborne Synthetic Aperture Radars (SARs) to generate wide swath imagery. ScanSAR involves the radar beam of the SAR being electronically steered or scanned to illuminate multiple sub-swaths.

[0003] The design of a ScanSAR mode must take into account multiple timing constraints: the integration time required by the azimuth resolution (also known as dwell time); the two-way slant range time (typically much smaller than the integration time); the ScanSAR cycle time for covering all sub-swaths without missing coverage; and receive windows for avoiding transmit pulses and nadir ambiguities.

[0004] Usually, a ScanSAR mode uses a radar transmitting over one frequency band centred at a particular carrier frequency to receive echoes to obtain an image, wherein the transmission of the radar is a series of pulses which form a burst, the radar beam is aimed at a ground range of interest, and the burst covers a wide area on the ground. This results in acquiring a single burst image.

[0005] However, in some circumstances there is a need to acquire two (or more) images, during the same time period but at different frequencies.

[0006] ScanSAR modes may also transmit radar pulses in at least two different polarization states, i.e., “multi-polarization”. In some circumstances there may also be a need to acquire two (or more) images during the same period at different transmit polarizations, and in some circumstances there may be a need to acquire two (or more) during the same time period at different frequencies and polarizations.

[0007] As well, the particular ratio of azimuth resolution to radiofrequency (RF) wavelength for a given scenario determines the dwell ratio (ratio of dwell time to two-way return-time) which alters the characteristics required for image acquisition using the ScanSAR mode. The different dwell ratios scenarios allow for adaptation of beam mode design.

[0008] Accordingly, there is a need for systems and methods for adapting the beam mode design to specific scenarios which overcome the lack of such beam mode designs in the existing systems and methods.Summary

[0009] Provided herein is a method of beam mode design for multi-frequency and / or multi-polarization scanning synthetic aperture radar (ScanSAR) at very coarse resolution, the method including receiving, at a beam mode design application, missionspecific beam mode design parameters; selecting, based on the mission-specific beam mode design parameters, a subset of beam mode configurations from a beam mode configuration space, wherein: (i) for the case when the ratio of azimuth dwell time to pulse two-way return time is <1 , the subset of beam mode configurations includes configurations that disregard pulse transmission window timing constraints when deconflicting pulse timing; and (ii) for the case when the ratio of azimuth dwell time to pulse two-way return time is <1 / 2, the subset of beam mode configurations includes configurations that allow two or more bursts transmission intervals to occur consecutively without intervening burst receive intervals; characterizing, by the beam mode design application, a possible synthetic aperture radar (SAR) performance based on the missionspecific beam mode design parameters and the subset of beam mode configurations; generating, by the beam mode design application, a plurality of outputs defining a possible mission-specific beam mode; iteratively feeding back the plurality of outputs to the beam mode design application as inputs for further characterizing possible SAR performances; and outputting, by the beam mode application, a compliant missionspecific beam mode.

[0010] The mission-specific beam mode design parameters may include the goal SAR performance for the mission, mission parameters, and payload parameters.

[0011] The goal SAR performance parameters may include resolution, swath, image quality, and number of looks.

[0012] The mission parameters may include at least one of: orbit parameters, incidence angle range, spatial and temporal coverage, and surface type.

[0013] The payload parameters may include at least one of: antenna dimensions and wavelengths.

[0014] The plurality of outputs may include estimated SAR performance, beam mode configuration, and miscellaneous parameters.

[0015] The estimated SAR performance output may include at least one of: resolution, swath, and image quality metrics.

[0016] The beam mode configuration output may include at least one of: number of beams, number of stepped receive beams and beam timing.

[0017] The miscellaneous parameters may include at least one of: data rates and SAR system performance.

[0018] The method may further include sending the compliant beam mode to a SAR payload as instructions for acquiring images.

[0019] The method may further include outputting, along with the compliant beam mode, SAR system specifications including at least one of: downlink bandwidth requirements, onboard memory requirements, and power consumption parameters.

[0020] A system is also provided comprising a data storage device and one or more processors in communication with the data storage device, the one or more processors configured to execute any of the foregoing methods.

[0021] A system for beam mode design for scanning synthetic aperture radar (ScanSAR) at very coarse resolution is also provided. The system includes: a data storage device; and one or more processors in communication with the data storage device. The one or more processors are configured to execute a beam mode design application, the beam mode design application configured to: receive mission-specific beam mode design parameters; receive a selection of a subset of beam modeconfigurations from a beam mode configuration space, wherein: (i) for the case when the ratio of azimuth dwell time to pulse two-way return time is <1 , the subset of beam mode configurations includes configurations that disregard pulse transmission window timing constraints when deconflicting pulse timing; and (ii) for the case when the ratio of azimuth dwell time to pulse two-way return time is <1 / 2, the subset of beam mode configurations includes configurations that allow two or more burst transmission intervals to occur consecutively without intervening burst receive intervals; characterize a possible synthetic aperture radar (SAR) performance based on the mission-specific beam mode design parameters and the subset of beam mode configurations; and generate a plurality of outputs defining a possible mission-specific beam mode.

[0022] Other aspects and features will become apparent to those ordinarily skilled in the art, upon review of the following description of some exemplary embodiments.Brief Description of the Drawings

[0023] The drawings included herewith are for illustrating various examples of articles, methods, and apparatuses of the present specification. In the drawings:

[0024] Figure 1 is a schematic diagram of a generic SAR satellite system for acquiring images of an area of interest, according to an embodiment;

[0025] Figure 2 is a schematic diagram of a beam mode design ScanSAR system, for determining a compliant beam mode design for a specific mission or scenario, according to an embodiment;

[0026] Figure 3A is a block diagram of a workflow for determining a compliant beam mode by a beam mode design application, according to an embodiment;

[0027] Figure 3B is a block diagram providing more detail for the inputs of Figure 3A, according to an embodiment;

[0028] Figure 3C is a block diagram providing more detail for the outputs of Figure 3A, according to an embodiment; and

[0029] Figure 4 is a flowchart of a method of determining a compliant beam design for a given scenario using a beam mode design application, according to an embodiment.Detailed Description

[0030] Various apparatuses or processes will be described below to provide an example of each claimed embodiment. No embodiment described below limits any claimed embodiment and any claimed embodiment may cover processes or apparatuses that differ from those described below. The claimed embodiments are not limited to apparatuses or processes having all of the features of any one apparatus or process described below or to features common to multiple or all of the apparatuses described below.

[0031] One or more systems described herein may be implemented in computer programs executing on programmable computers, each comprising 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, and without limitation, the programmable computer may be a programmable logic unit, a mainframe computer, server, and personal computer, cloud-based program or system, laptop, etc.

[0032] Each program is preferably implemented in a high-level procedural or object-oriented programming and / or scripting language to communicate with a computer system. However, the programs can be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language. Each such computer program is preferably stored on a storage media or a device readable by a general or special purpose programmable computer for configuring and operating the computer when the storage media or device is read by the computer to perform the procedures described herein.

[0033] A description of an embodiment with several components in communication with each other does not imply that all such components are required. On the contrary, a variety of optional components are described to illustrate the wide variety of possible embodiments of the present invention.

[0034] Further, although process steps, method steps, algorithms or the like may be described (in the disclosure and / or in the claims) in a sequential order, such processes, methods and algorithms may be configured to work in alternate orders. In other words,any sequence or order of steps that may be described does not necessarily indicate a requirement that the steps be performed in that order. The steps of processes described herein may be performed in any order that is practical. Further, some steps may be performed simultaneously.

[0035] When a single device or article is described herein, it will be readily apparent that more than one device / article (whether or not they cooperate) may be used in place of a single device / article. Similarly, where more than one device or article is described herein (whether or not they cooperate), it will be readily apparent that a single device / article may be used in place of the more than one device or article.

[0036] The following relates generally to the use of ScanSAR modes for image acquisition by synthetic aperture radars (SARs) and more particularly to the adaptation of beam mode design for specific dwell ratios scenarios.

[0037] A SAR mode is a payload configuration that is designed to acquire SAR raw data in a particular way to achieve certain imaging goals (quality, resolution, ground extent, number of ‘looks’), A SAR mode includes of a number of specification parameters that control (1 ) the 2D radar beam (pointing and shape); (2) characteristics of the transmitted signal (e.g. the ‘pulse’);(3) timing of the pulse transmissions and echo receive functions of the payload, and (4) polarization of the transmitted and received signals.

[0038] A ScanSAR mode is a SAR mode that defines a set of ‘beams’ each pointing at a different range of elevation angles and in a repeated sequence. These beams are used to acquire SAR raw data that spans the union of the per-beam elevations, thus achieving a wider elevation swath coverage than is possible with a single beam.

[0039] SAR signals are transmitted over a radio frequency band characterized by a centre frequency and a bandwidth. Single frequency systems transmit signals at one RF centre frequency, while multi frequency systems transmit signals at two or more RF centre frequencies with frequency separations that are wider than the bandwidth. Multi frequency systems effectively acquire multiple sets of images, one for each RF frequency and this allows the measured target backscatter to be characterized at these frequencies which can be exploited by some SAR applications. This concept can be generalized to multi-frequency systems, with a set of images at each RF frequency.

[0040] The following relates to adaptations of ScanSAR design when the ratio of azimuth resolution to radiofrequency (RF) wavelength, or “8a / A”, is high. Said ratio determines the dwell ratio, pdweii, which is the ratio of the dwell time, fdweii, to the two-way return time, feR.

[0041] The dwell ratio can be used to define three cases:

[0042] 1 . Conventional case (dwell > 1): this is the typical case for SAR beam modes and results in a time overlap between the period along orbit when pulses are transmitted and when they are received. Note that for past and current spaceborne SARs using ScanSAR this dwell ratio is substantially greater than 1. This condition generally requires that the set of ScanSAR bursts be acquired sequentially and that the pulse transmission and receive windows be deconflicted by selecting an appropriate pulse repetition frequency (PRF) and / or swath range extent.

[0043] 2. Pulse deconfliction case ( / ,2<pdweii^ 1 ): For this case, the periods along orbit when pulse transmission and reception occur do not overlap. This ‘deconflicts’ the pulse timing and allows greater flexibility in selecting the PRF and / or the sub-swath range extent. An additional benefit is that range ambiguities are reduced or eliminated.

[0044] 3. Burst interleave case (pdweii^ ): For this case, in addition to pulse deconfliction, the low dwell ratio leaves enough time along orbit to potentially transmit pulses for more than one burst (either different sub-swath or RF frequency) before pulse reception occurs for those transmitted pulses. Interleaving reduces the total time required to acquire a cycle of ScanSAR bursts. Pulses from another polarization could also be interleaved but these would likely contribute to range ambiguities.

[0045] Cases 2 and 3 above only occur when the product of RF center frequency and azimuth resolution is high.

[0046] In particular, the beam mode design described herein is for adaptation of beam mode design when the dwell ratio is sufficiently low (i.e., less than or equal to 1 ) to achieve: i) deconfliction of a SAR pulse transmit and receive, thus allowing more flexibility in mode design (case 2 above) ii) reduction of range ambiguities when transmit and receive occur in distinct time periods, and iii) potential reduction of ScanSAR cycle time(in a burst interleave case, case 3 above), which generally improves SAR imaging performance (i.e., better ambiguity ratios and better noise performance). However, the adaptations described herein may be applied in other scenarios as well.

[0047] The systems and methods described herein provide a beam mode design which enables characterization of a mission-compliant beam mode design for a specific mission or scenario, in particular those scenarios described above wherein the dwell ratio is 1 or below.

[0048] A beam mode design application takes as input various parameters, including mission parameters, payload parameters, and a goal SAR performance, as well as the possible beam mode design parameters which exist within a given SAR beam mode space, and iteratively characterizes SAR performance, finally providing various outputs including a beam mode configuration(s), estimated SAR performance, and other miscellaneous parameters required for a SAR satellite to acquire the desired images.

[0049] Within the SAR beam mode space, changing the value of certain parameters may improve certain aspects of image acquisition at the expense of other aspects. Therefore, an iterative process is used to determine a mission-compliant beam mode which serves to balance said aspects. The set of parameters and particular values used to define a beam mode is termed a beam mode configuration.

[0050] For a conventional beam mode design (i.e., dwell ratio > 1 ), the beam mode is confined to a specific subset of beam mode configurations within the beam mode parameter space. Herein, the beam mode design application instead allows for an additional set of beam mode configurations which are outside of the parameter space of the conventional beam mode design.

[0051] For a multi-frequency and / or multi-polarization SAR scenario with burst interleaving the novel subset of beam mode configurations allows for burst transmit times to be sequenced so that they are interleaved. Interleaving is more time efficient and, therefore, reduces what is known as the ScanSAR burst cycle time. Reducing the ScanSAR burst cycle time reduces the Doppler bandwidth occupied by a given burst and, therefore, reduces the required pulse repetition frequency (PRF) thus providing better performance within the beam mode design trade space (i.e., allows for lower PRFs,potentially reducing range ambiguity ratio). Using less Doppler bandwidth may also reduce azimuth ambiguity ratios by only using the high-gain portions of the beam.

[0052] During iterative SAR performance characterization, the beam mode design application may undergo multiple rounds of characterization wherein the estimated SAR performance for a given beam mode configuration, as well as the given beam mode configuration parameters, are fed back into the application as inputs for further beam mode characterization.

[0053] The final outputs (final iteration or characterization): (i) characterize the system image quality, (ii) and serve as inputs for SAR system specification budgets such as downlink bandwidth, onboard memory, and power consumption. As well, the final outputs specify how the SAR payload is commanded (sequence of payload actions) to achieve the given beam mode.

[0054] While the beam mode design described herein often refers to dualfrequency ScanSAR beam mode design, the systems and methods are applicable to both single frequency and dual / multi-frequency ScanSAR beam mode design. As well, while generally multi-frequency ScanSAR is referred to herein, it is to be understood that the systems and methods are also applicable to multi-polarization ScanSAR and multi- frequency / multi-polarization ScanSAR beam mode design.

[0055] Referring now to Figure 1 , shown therein is a generic ScanSAR satellite system 100 for acquiring images of an area of interest 102.

[0056] In Figure 1 , a satellite 104 with a synthetic aperture radar (SAR) system 110 acquires images of an area of interest 102. The area of interest may be ground or water.

[0057] In the embodiment of Figure 1 , the satellite 104 sends the data directly to computing devices 120.

[0058] In other embodiments, the satellite 104 may send and / or receive data through a receiving station on the ground. In other embodiments, the satellite may send and / or receive data through a cloud server. In other embodiments, the satellite 104 may send and / or receive data through a relay satellite(s).

[0059] In some embodiments, at least some data may be processed onboard by the satellite 104.

[0060] The system 100 of Figure 1 is an example of a system for acquiring, processing, and using SAR images, but does not describe control of the SAR system 110 or design of the beam mode used for image acquisition.

[0061] Referring now to Figure 2, shown therein is a beam mode design ScanSAR system 200, for determining a compliant beam mode design for a specific mission or scenario. System 200 represents a simplified SAR system, which only shows the components of the system necessary for designing and implementing a ScanSAR beam mode.

[0062] System 200 includes a satellite 204 with an SAR payload 210 which can acquire images of an area of interest.

[0063] The satellite 204 is communicatively coupled to at least one computing device 220 which includes at least one processor which executes a beam design application which is stored in at least one memory.

[0064] As described above, various other components, e.g., cloud servers, relay satellites, etc., may be intervening components between the satellite 204 and the at least one computing device 220.

[0065] In Figure 2, the computing device is shown as a single laptop, however, in other embodiments the at least one computing device may include any configuration of laptops, servers, cloud servers, desktops, mobile devices, etc., which are capable of running the beam mode design application.

[0066] The at least one computing device 220 receives various parameters as input for iteratively determining a compliant beam mode for a given mission, using a beam mode design application, and outputs the compliant beam mode configuration information to the satellite 204.

[0067] The SAR payload 210 receives the compliant beam mode configuration information as instructions and operates in the compliant beam mode to acquire SAR data.

[0068] In Figure 2, the SAR payload 210 receives beam mode configuration data from the at least one computing device 220.

[0069] The beam mode design application of the at least one computing device 220 may perform beam mode design automatically wherein an order is received and the application performs beam mode design without human activation or the process may be triggered by a human operator. The process may be performed by the at least one computing device autonomously, wherein no human intervention is required, the process may be performed semi-autonomously wherein some human input is required, or the process may be performed largely with human input.

[0070] Figure 3A is a block diagram of a workflow 300 for determining a compliant beam mode by a beam mode design application. The workflow includes inputs 310, performance characterization 320, beam mode configuration space 330, and outputs 340.

[0071] Figure 3B shows more detail of the inputs 310, while Figure 3C shows more detail of the outputs 340.

[0072] In workflow 300, the beam mode design application receives various inputs 310 for a performance characterization process 320.

[0073] As seen in Figure 3B the beam mode design application inputs 310 include a goal SAR performance 311 , which represents the desired parameters for the output of the ScanSAR acquisition, e.g., resolution, swath, number of looks, etc., mission parameters 312, which include orbit parameters, incidence angle range, etc., and payload parameters 313, which include antenna dimensions, wavelengths, maximum RF transmit power, maximum pulse duty cycle, etc. Taken together the inputs 310 inform the performance characterization for the particular SAR payload and mission, and ultimately the final compliant beam mode design which is sent as instructions to the SAR payload.

[0074] The performance characterization 320 also takes as input a beam mode configuration space 330 which includes all possible beam mode configurations. Each beam mode configuration corresponds to one possible configuration of the SAR payload for acquiring a SAR dataset. For a conventional SAR acquisition (i.e. , where the ratio of azimuth dwell time to pulse two-way return time is 1 or more), the SAR payload isrestricted to conventional beam mode configurations 332 within the beam mode configuration space 330. However, when the beam mode is for a non-conventional acquisition (i.e., acquisition corresponding to the pulse deconfliction case or the burst interleaving case), the beam mode configuration includes non-conventional beam mode configurations 334 based on the inputs 310. Non-conventional beam mode configurations 334, when combined with the conventional beam mode configurations 332 results in a larger subset of beam mode configurations considered during performance characterization, 320. The non-conventional configurations 334 allows for non- conventional beam mode design for interleaved bursts and / or SAR timing that is less restrictive due to pulse deconfliction.

[0075] Both the conventional beam mode configurations 332 and the non- conventional beam mode configurations 334 are defined by constraints. The constraints include the a priori inputs into the process. The allowable space for the conventional beam mode configurations 332 and non-conventional beam mode configurations 334 is fixed. The process of beam mode design uses the pre-defined conventional beam mode configurations 332 and non-conventional beam mode configurations 334 and, therefore, pre-defined subset of possible configurations and attempts to find the compliant beam mode configuration instance within the union of conventional 332 and non-conventional configurations 334.

[0076] In embodiments where the ratio of azimuth dwell time to pulse two-way return time is <1 , the possible non-conventional beam mode configurations disregard pulse transmission window timing constraints to deconflict pulse timing.

[0077] In embodiments where the ratio of azimuth dwell time to pulse two-way return time is <0.5, the possible non-conventional beam mode configurations allow two or more burst transmission intervals to occur consecutively without intervening burst receive intervals.

[0078] The performance characterization 320 generates outputs 340 which include estimated SAR performance 341 , beam mode configuration 342, and miscellaneous parameters 343, as shown in Figure 3C. The estimated SAR performance 341 outputs include resolution, swath, noise equivalent sigma zero (NESZ), range ambiguities,azimuth ambiguities, etc. The beam mode configuration 342 outputs include the number of beams, number of stepped receive beams, pulses and pulse repetition frequency per beam, beam shape, etc. The miscellaneous parameters 343 may include parameters such as data rates.

[0079] The outputs 340 may be fed back into the performance characterization 320 in an iterative process until a compliant beam design, which the performance characterization seemingly cannot improve upon, is determined.

[0080] For a dual-frequency, multi-look, coarse resolution ScanSAR mode beam design process, a burst interleaving approach for a large resolution / wavelength ratio would result in more efficient timing to support the multi-frequency and multi-look characteristics, and will add flexibility to the mode design (e.g., for parameters such as PRFs). The approach also lowers range ambiguities and reduces ScanSAR cycle time for improved ambiguities, signal-to-noise ratio (SNR), and other factors. The burst interleaving approach is also appropriate for multi-polarization coarse ScanSAR mode beam design.

[0081] Figure 4 is a flow diagram of a method 400 of determining a compliant beam design for a given scenario using a beam mode design application. The scenario includes the use of a known SAR payload for a defined image acquisition of an area of interest.

[0082] At 402, the beam mode design application receives mission-specific beam mode design parameters as inputs. As described above, the parameters include the goal SAR performance for the mission (e.g. resolution, swath, number of looks, etc.), mission parameters (e.g. orbit parameters, incidence angle range, spatial and temporal coverage, surface type, etc.) and payload parameters (e.g. antenna dimensions, wavelengths, etc.). Other parameters may be included beyond these.

[0083] At 404, the beam mode design application receives a set of beam mode design parameters and selects the subset of parameter values (i.e. the beam mode configurations) that are possible for the SAR payload. The beam mode configurations represent a subset of the entire beam mode configuration space. The subset is determined from the mission-specific beam mode design parameters and constraints. That is, the beam mode configurations are the possible beam mode configurations whichexist within the union of predefined conventional and non-conventional configurations, as described above for Figure 3A.

[0084] At 406, the beam mode design application characterizes a possible SAR beam mode performance based on the mission-specific beam mode design parameters and the beam mode configurations (as defined by the union of conventional and non- conventional configurations).

[0085] At 408, the beam mode design application generates outputs which define a possible mission-specific beam mode. The outputs include estimated SAR performance (e.g. resolution, swath, other image quality metrics, etc.), beam mode configuration (e.g. number of beams, number of stepped receive beams, etc.), and miscellaneous parameters (e.g. data rates, SAR system performance, etc.).

[0086] As the beam mode design application uses an iterative process, the outputs may either be taken as further inputs into the characterization step or can be taken as a compliant beam design to be used in the mission.

[0087] Therefore, in Figure 4, at 410, the generated outputs are fed back to 406 to be used as inputs for further characterizing a possible SAR performance.

[0088] At 412, once the iterative characterization process has reached a peak estimated SAR performance, the beam mode design application outputs a compliant mission-specific beam mode. The compliant beam mode can then be sent to the SAR payload to be used to acquire images as the mission requires. The compliant beam mode depends on the specific mission, wherein for different missions and satellite systems the most important performance parameters will differ.

[0089] The compliant beam mode may be optimized during the iterative design process, with the final design being chosen based on several factors which may include image quality as well as the cost of the mission. The design process compares possible SAR performances against mission requirements and identify deficiencies, and then iterates until the mission requirements are met. Therefore, the compliant beam mode may not result in the highest quality of imaging possible as a more important requirement may be reducing costs or computational requirements.

[0090] Along with defining a compliant beam mode, the final iteration of the characterization process outputs also includes characterization of the system image quality, as well as inputs for SAR system specification budgets, including downlink bandwidth, onboard memory, and power consumption parameters.

[0091] While the above description provides examples of one or more apparatus, methods, or systems, it will be appreciated that other apparatus, methods, or systems may be within the scope of the claims as interpreted by one of skill in the art.

Claims

Claims:1 . A method of beam mode design for scanning synthetic aperture radar (ScanSAR) at very coarse resolution, the method comprising: receiving, at a beam mode design application, mission-specific beam mode design parameters; selecting, based on the mission-specific beam mode design parameters, a subset of beam mode configurations from a beam mode configuration space, wherein:(i) for the case when the ratio of azimuth dwell time to pulse two-way return time is <1 , the subset of beam mode configurations includes configurations that disregard pulse transmission window timing constraints when deconflicting pulse timing; and(ii) for the case when the ratio of azimuth dwell time to pulse two-way return time is <1 / 2, the subset of beam mode configurations includes configurations that allow two or more burst transmission intervals to occur consecutively without intervening burst receive intervals; characterizing, by the beam mode design application, a possible synthetic aperture radar (SAR) performance based on the mission-specific beam mode design parameters and the subset of beam mode configurations; and generating, by the beam mode design application, a plurality of outputs defining a possible mission-specific beam mode.

2. The method of claim 1 , wherein the mission-specific beam mode design parameters are for multi-frequency ScanSAR.

3. The method of claim 1 , wherein the mission-specific beam mode design parameters are for multi-polarization ScanSAR.

4. The method of claim 1 , wherein the mission-specific beam mode design parameters are for multi-frequency and multi-polarization ScanSAR.

5. The method of claim 1 , further comprising iteratively feeding back the plurality of outputs to the beam mode design application as inputs for further characterizing possible SAR performances.

6. The method of claim 5, further comprising outputting, by the beam mode application, a compliant mission-specific beam mode.

7. The method of claim 1 , wherein mission-specific beam mode design parameters include a goal SAR performance for the mission, mission parameters, and payload parameters.

8. The method of claim 7, wherein the goal SAR performance parameters include resolution, swath, image quality, and number of looks.

9. The method of claim 7, wherein the mission parameters include at least one of: orbit parameters, incidence angle range, spatial and temporal coverage, and surface type.

10. The method of claim 7, wherein the payload parameters include at least one of: antenna dimensions and wavelengths.11 . The method of claim 1 , wherein the plurality of outputs include estimated SAR performance, beam mode configuration, and miscellaneous parameters.

12. The method of claim 11 , wherein the estimated SAR performance output includes at least one of: resolution, swath, and image quality metrics.

13. The method of claim 11 , wherein the beam mode configuration output includes at least one of: number of beams, number of stepped receive beams and beam timing.

14. The method of claim 11 , wherein the miscellaneous parameters include at least one of: data rates and SAR system performance.

15. The method of claim 1 further comprising: sending the compliant beam mode to a SAR payload as instructions for acquiring images.

16. The method of claim 1 , further comprising: outputting, along with the compliant beam mode, SAR system specifications including at least one of: downlink bandwidth requirements, onboard memory requirements, and power consumption parameters.

17. A system comprising a data storage device and one or more processors in communication with the data storage device, the one or more processors configured to execute the method of any of claims 1 -16.

18. A system for beam mode design for scanning synthetic aperture radar (ScanSAR) at very coarse resolution, the system comprising: a data storage device; and one or more processors in communication with the data storage device, the one or more processors configured to execute a beam mode design application, the beam mode design application configured to: receive mission-specific beam mode design parameters;receive a selection of a subset of beam mode configurations from a beam mode configuration space, wherein:(i) for the case when the ratio of azimuth dwell time to pulse two-way return time is <1 , the subset of beam mode configurations includes configurations that disregard pulse transmission window timing constraints when deconflicting pulse timing; and(ii) for the case when the ratio of azimuth dwell time to pulse two-way return time is <1 / 2, the subset of beam mode configurations includes configurations that allow two or more burst transmission intervals to occur consecutively without intervening burst receive intervals; characterize a possible synthetic aperture radar (SAR) performance based on the mission-specific beam mode design parameters and the subset of beam mode configurations; and generate a plurality of outputs defining a possible mission-specific beam mode.

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