WO2025088046A1

WO2025088046A1 - System and method for single pulse detection

Info

Publication number: WO2025088046A1
Application number: PCT/EP2024/080092
Authority: WO
Inventors: Pete Charles BLACKER
Original assignee: MDA Space and Robotics Ltd
Current assignee: MDA Space and Robotics Ltd
Priority date: 2023-10-25
Filing date: 2024-10-24
Publication date: 2025-05-01
Anticipated expiration: 2026-04-25

Abstract

Provided are systems, methods and devices for determining information of a target object. The target object includes a plurality of retroreflectors placed on the target object. The method includes detecting a light curve of a pulse reflected from the target object with a lidar system from a distance to produce captured lidar data, processing the captured lidar data to identify a retroreflector arrangement by comparing the retroreflector arrangement to a retroreflector arrangement database, and determining object information by applying an estimation algorithm to the identified retroreflector arrangement.

Description

SYSTEM AND METHOD FOR SINGLE PULSE DETECTION

Technical Field

[0001] The following relates generally to a device, system and associated method for the determination of spacecraft information from long distances, and specifically, to single pulse determination using reflective markers.

Introduction

[0002] It may be advantageous to determine information such as the pose, partialpose, attitude, identification or identification code of a spacecraft or space object in flight or orbit from a distance.

[0003] Current methods for such pose determinations may be limited in detection range, may have a limited field of view, require large equipment and/or heavy optics, or may be otherwise complex and/or expensive. Existing methods may require the passive client to be imaged to determine pose which necessitate telescopes for long range. For example, it may be desirable for a system that does not require the client to be resolved in an image to determine partial pose.

[0004] Accordingly, there is need for a device and method which may overcome at least some of the disadvantages of existing methods.

Summary

[0005] Provided is a system for determining information of a target object. The system includes a plurality of retroreflectors on the target object, a lidar system for detecting a light curve of a pulse reflected from the object from a distance to produce captured lidar data, and a processor device comprising a memory and processor, the processor device configured to process the captured lidar data to identify a retroreflector arrangement by comparing the retroreflector arrangement to a retroreflector arrangement database, and determine object information by applying an estimation algorithm to the identified retroreflector arrangement.

[0006] Provided is a method for determining information of a target object. The target object includes a plurality of retroreflectors placed on the target object. The method includes detecting a light curve of a pulse reflected from the target object with a lidar system from a distance to produce captured lidar data, processing the captured lidar data to identify a retroreflector arrangement by comparing the retroreflector arrangement to a retroreflector arrangement database, and determining object information by applying an estimation algorithm to the identified retroreflector arrangement.

[0007] The object information may include pose, and the estimation algorithm may be a pose estimation algorithm.

[0008] The object information may include a spacecraft identification code, and the estimation algorithm may be a spacecraft identification algorithm.

[0009] The target object may include a pattern that includes a linear array of retroreflectors.

[0010] The pattern may include two orthogonal linear arrays of retroreflectors.

[0011] The target object may be detected with a single lidar reflection.

[0012] The target object may be a spacecraft.

[0013] A spacing of each retroreflector arrangement may include a unique pattern that aligns with a known arrangement within the retroreflector arrangement database, such that each retroreflector arrangement is identified.

[0014] Each retroreflector arrangement may be associated with a certain face, surface and/or axis of a specific target object.

[0015] The pose about two axes may be determined.

[0016] 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

[0017] The drawings included herewith are for illustrating various examples of articles, methods, and apparatuses of the present specification. In the drawings:

[0018] Figure 1 is a single pulse pose determination system, according to an embodiment; [0019] Figure 2 is a depiction of a single linear set of retroreflectors of Figure 1 , operating at three angles relative to the target object, according to an embodiment;

[0020] Figure 3A is a chart depicting an output of the system of Figure 2, at the first configuration, according to an embodiment;

[0021] Figure 3B is a chart depicting the output of the system of Figure 2, at the second configuration, according to an embodiment;

[0022] Figure 3C is a chart depicting the output of the system of Figure 2, at the third configuration, according to an embodiment;

[0023] Figure 4 is a depiction of a target object having two orthogonal linear retroreflector arrangements, according to an embodiment;

[0024] Figure 5 is a block diagram of a retroreflector arrangement of the system of Figure 1 , according to an embodiment;

[0025] Figure 6 is front view of a retroreflector assembly having an integrated retroreflector arrangement, according to an embodiment;

[0026] Figure 7 is a detail block diagram of the processor device of Figure 1 , according to an embodiment; and

[0027] Figure 8 is a flow chart depicting a method of using the system of Figures 1-3, according to an embodiment.

Detailed Description

[0028] 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.

[0029] 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.

[0030] When a single device or article is described herein, it will be readily apparent that more than one device I article (whether or not they cooperate) may be used in place of a single device I 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 I article may be used in place of the more than one device or article.

[0031] Described generally herein is a system and method for single pulse determination. A target object is fitted with a plurality of retroreflectors, positioned on the target object in a predetermined pattern.

[0032] A light detection and ranging device (lidar) emits a single pulse signal, and captures the returned waveform of the reflected signal. Any class of lidar which can report full reflected pulse shape with high temporal resolution may be used. A laser range finder, a lidar Either Flash, Scanning, or laser rangefinder may be used.

[0033] The target object is then detected from a distance using the lidar system.

[0034] The method described herein may advantageously avoid the need to do imaging or resolving a spatial visual representation of an object by operating on light curves from single points of illumination.

[0035] The lidar system receives a return signal, bounced off the target object.

[0036] The retroreflector pattern is clearly present in the returned flash lidar signal, due to the varying distances of each retroreflector due to the pose, or partial-pose of the target object. This pattern or arrangement may be compared to known patterns or arrangements to identify known retroreflector arrangements. The target object may be fitted with multiple linear arrangements of retroreflectors, at known angles to one another. By comparing detected angles of known retroreflector arrangements to known angles, and distances object pose relative to the lidar system may be determined. By way of example, this system and associated method may be applied to the pose detection of objects 50km away or more.

[0037] The methods and devices described herein may allow the detection of a spacecraft identification code (e.g., Registration Plate) in addition to or instead of the pose information.

[0038] Referring now to Figure 1 , pictured therein is a block diagram of a single pulse estimation system 100, according to an embodiment. The system 100 includes a target object 102 for being detected. The system 100 includes a plurality of retroreflectors 104 on the target object 102. The system 100 includes the lidar device or system 106 for emitting and detecting light. The system 100 includes a processor device 108 for processing light data that is captured by the lidar system 106.

[0039] The lidar system 106 detects a light curve of a pulse reflected from the target object 102, from a distance, to produce captured lidar data. Target object 102 includes an object which may be desirable to determine the pose or attitude of at a distance. Target object 102 may include a spacecraft, such as a satellite. Target object 102 includes a plurality of retroreflectors 104 coupled to target object 102.

[0040] Retroreflectors 104 include objects coupled to target object 102 which reflect electromagnetic radiation, such as visible light, emitted by the lidar system 106. The retroreflectors 104 include reflectors of electromagnetic radiation so that the relative distances of retroreflectors 104 are reliably detected and determined by lidar system 106.

[0041] Retroreflectors 104 are coupled to target object 102 in a preset pattern or arrangement. In some examples, retroreflectors 104 may be coupled to target object 102 in a linear arrangement, as shown in Figure 1. For example, five (5) retroreflectors 104 are placed on target object 102, in an evenly spaced manner.

[0042] In some examples, multiple linear arrangements of retroreflectors 104 are present. In such examples, three mutually orthogonal linear arrangements of retroreflectors 104 may be present.

[0043] Each orthogonal linear arrangement differs slightly. For example, the spacing of each arrangement is distinct, such that each linear array of retroreflectors 104 is differentiated by comparison of detected retroreflector 104 arrangement to a retroreflector arrangement database. In other examples, retroreflector 104 arrangements may include different numbers of individual retroreflectors, as pictured in Figure 1. The specific arrangement of the retroflectors may correspond to the spacecraft identification code of the target object 102.

[0044] In some examples, retroreflectors 104 are arranged according to a pattern comprising information to determine error correction. For example, the arrangement of retroreflectors 104 are configured such that if several retroreflectors 104 are missing or unable to be detected by system 100, the unique array of retroreflectors 104 are identified.

[0045] The lidar system 106 includes an emitter to emit light. The lidar system 106 includes at least one sensor to detect the emitted light after reflecting off of the retroreflectors 104 on the target object 102.

[0046] The lidar system 106 records the pulse shape of a time-of-flight laser reflection. For example, the lidar system 106 is able to record the pulse shape of a time- of-flight laser reflection with at least 15cm resolution. Lidar system 106 comprises full wave recording capabilities.

[0047] Processor device 108 includes a computing device coupled to lidar system 106. The processor device 108 processes data captured by lidar system 106. The processor 108 processes the captured lidar data to identify retroreflector engagement by comparing the retroreflector arrangement to a retroreflector database. Processor device 108 accesses a database of known retroreflector 104 arrangements. The processor device 108 processes lidar data received from lidar system 106.

[0048] The processor 108 differentiates the signals of each linear pattern from the combined signal of all of them which will be contained in the light curve from the lidar sensor.

[0049] The processor 108 determines object information by applying an estimation algorithm to the identified retroreflector arrangement. The object information includes pose or partial-pose information. The estimation algorithm is a pose estimation algorithm. The estimation algorithm may also be a partial-pose estimation algorithm. [0050] In addition or alternatively, the object information includes a spacecraft identification code. The estimation algorithm is a spacecraft identification algorithm.

[0051] Referring now to Figure 2, pictured therein is a depiction of a system 101 of a single pulse estimation system, in accordance with another embodiment. The system 101 includes three various poses relative to the target object 102c, according to an embodiment.

[0052] Pictured in Figure 2 is a lidar system positioned at three distinct poses (106a, 106b, 106c) relative to the target object 102c. The lidar systems 106a, 106b, 106c may be the lidar system 106 as described with reference to Figurel . Each lidar system 106a, 106b, 106c is at a differing angle or pose relative to target object 102c.

[0053] Lidar system 106a is at a positive angle relative to target object 102c. Lidar system 106b is at a neutral angle relative to target object 102c. Lidar system 106c is at a negative angle relative to target object 102c.

[0054] Target object 102c includes three retroreflectors 104a, 104b, and 104c, in a linear arrangement, with known predetermined relative spacing.

[0055] Each lidar system 106a, 106b, 106c may detect target object 102c, and the retroreflectors 104a, 104b and 104c coupled to target object 102c.

[0056] Shown relative to lidar system 106a are imaging paths 126a, 126b and 126c, associated with retroreflectors 104a, 104b, and 104c respectively.

[0057] Paths 126a, 126b and 126c each include differing lengths, wherein 126a, 126b and 126c comprise ascending lengths. Due to the fixed speed of light, and these varying lengths, the signal associated with each retroreflector 104a, 104b and 104c may be received at different points in time. This time difference corresponds to target object 102c pose relative to lidar system 106, as the pose of target object 102c relative to lidar system 106 alters the relative distances of each retroreflector 104 to lidar system 106a.

[0058] While not pictured in Figure 2, similar imaging paths are present for lidar system 106b and 106c, differing according to relative angles of lidar systems and target object 102c. [0059] Referring now to Figures 3A-3C, pictured therein are charts 300a, 300b, 300c, depicting the outputs 118a, 118b and 118c of lidar systems 106A-106C of Figure 2 respectively, according to an embodiment. Each chart includes a y-axis 302, depicting output amplitude, and an x-axis 304, depicting time.

[0060] As described previously, due to the varying imaging path lengths, signals associated with each retroreflector may be received by the lidar system 106 at differing times, depending on the relative angle of the lidar system 106 and target object 102c. For example, for lidar system 106b, corresponding to a neutral relative angle between the lidar system and target object, the output 118b of Figure 3B generally comprises a single square signal, as all three retroreflector 104a, 104b, 104c are generally a similar distance away from lidar system 106b.

[0061] In contrast, for lidar system 106a, corresponding to a positive relative angle between the lidar system and target object, the output 118a of Figure 3A generally comprises three square pulses, as all three retroreflectors 104a, 104b, 104c are generally differing distances away from lidar system 106b. The first two pulses, corresponding to retroreflectors 104a, 104b are closer than the last two pulses, corresponding to retroreflectors 104b, 104c. This is due to the fact that retroreflectors 104a, and 104b are closer to one another than retroreflectors 104b, and 104c. This same applies to output 118c of lidar system 106c, however, the order of pulses is reversed due to the negative relative angle of lidar system 106c to target object 102c.

[0062] By applying a pose estimation algorithm, which accounts for this distance between pulses, the relative 2D angle of target object 102c relative to lidar system 106, may be determined. This algorithm may apply calibration information according to the overall distance between target object 102c and lidar system 106, as well as properties of the retroreflector arrangement (e.g., spacing, and overall length). The algorithm may measure center to center distances of each pulse, according to some embodiments.

[0063] While the example outputs of Figure 3 show clear square waveform signals as demonstrative examples, real world examples may comprise differing outputs accounting for real world error and uncertainty. For example, noise may be present, or waveform signals may be rounded or otherwise distorted. [0064] While the example of Figures 2-3 shows a single axis angle determination, in other examples, multiple linear arrangements of retroreflectors may be present (e.g., in an orthogonal linear configuration), allowing for partial-pose according to multiple axis of rotation to be determined.

[0065] Referring now to Figure 4, therein is an example of a target object 102b comprising two orthogonal, linear retroflector arrangements 112a and 112b (collectively referred to as retroflector arrangements 112). The retroreflector arrangements 112 each comprise a configured linear pattern. The spacing of each retroreflector arrangement 112 comprises a unique pattern. The spacing of each retroreflector arrangement 112 may uniquely align with a known arrangement within a retroreflector arrangement database, such that each arrangement may be identified. In some examples, each arrangement may be associated with a certain face, surface and/or axis of a specific target object.

[0066] In some examples, the total number of retroreflectors present in a linear arrangement 112 may differ from those shown and described herein.

[0067] By performing the operation described above in reference to Figures 2-3 on the target object 102b of Figure 4, the pose of the target object 102b about two orthogonal rotational axes may be determined.

[0068] Referring now to Figure 5, pictured therein is an example of retroflector arrangements 112c and 112d (collectively referred to as retroflector arrangements 112). The retroreflector arrangements 112 each comprise a configured linear pattern. The width and spacing of each retroreflector arrangement 112 comprises a unique pattern. The spacing of each retroreflector arrangement 112 may uniquely align with a known arrangement within a retroreflector arrangement database, such that each arrangement may be identified. In some examples, each arrangement may be associated with a certain face, surface and/or axis of a specific target object. In some examples, the total number of retroreflectors present in a linear arrangement 112 may differ from those shown and described herein.

[0069] While Figure 5 illustrates the two separated return signals from the two orthogonal retroreflector patterns described in figure 4, these two signals will be mixed into a single light curve, and the processor runs the estimation algorithm to separate the signals.

[0070] Referring now to Figure 6, shown therein is a retroreflector assembly 204, according to an embodiment.

[0071] The retroreflector assembly 204 of Figure 6 comprises an integrated retroreflector arrangement array 206. This array 206 includes a number of discrete retroreflector areas, separated by areas that are not retroreflective, in a known pattern.

[0072] In some embodiments of the systems and methods described herein, a retroreflector assembly, such as assembly 204, may be affixed to a target object, instead of arrays of discrete, individual retroreflectors, as shown, for example, in the embodiment of Figure 1.

[0073] By using a retroreflector assembly such as assembly 204, retroreflector arrangements or arrays may be more compact, and may be affixed to a target object in a single step, without requiring precise individual placement of each retroreflector, simplifying manufacturing and assembly, and increasing reliability.

[0074] Referring now to Figure 7, shown therein is a depiction processor device 108. Processor device 108 comprises a processor 124 and memory 122.

[0075] Memory 122 comprises retroreflector database 116, lidar data 118 and an estimation algorithm 120.

[0076] Retroreflector database 116 comprises a database or repository of known retroreflector arrangements. Each retroreflector arrangement may be uniquely associated with a target object, as well as a specific axis, orientation, surface, face, and/or length. Each retroreflector arrangement may have a known overall length or distance between constituent retroreflectors for distance and length calibration.

[0077] Lidar data 118 comprises data captured by the lidar system 106 when imaging target object 102. Within lidar data 118, locations of retroreflectors 104 are visible, and may be identified using detection processing algorithms or methods. [0078] The method differentiates the signals of each linear pattern from the combined signal of all of them which will be contained in the light curve from the lidar sensor.

[0079] The method determines object information by applying the estimation algorithm 120 to the identified retroreflector arrangement. The object information includes pose. The estimation algorithm 120 may be a pose estimation algorithm. The estimation algorithm 120 may be a pose determination algorithm.

[0080] The estimation algorithm may include a target object identification algorithm to identify the target object from a plurality of target objects. More particularly, the system described herein may include a spacecraft identification algorithm to identify the spacecraft from a plurality of spacecraft. The retroreflectors include a pattern that is unique to the target spacecraft. The processor detects the identification of the spacecraft from the waveform. The spacecraft identification system may be used to check that the correct spacecraft is being tracked.

[0081] Estimation algorithm 120 received lidar data 118 and retroreflector database 116 data as an input and generates an output of the pose of objects of interest captured by lidar system 106.

[0082] Processor 124 comprises any general-purpose digital processor known in the art. Processor 124 may be provided with data and program instructions of memory 122, for execution.

[0083] While in the embodiment of Figure 7, retroreflector database 116, lidar data 118 and estimation algorithm 120 are shown as present on internal memory of processor device 106, in other examples, these components may be present on other hardware to which processor device 108 is coupled, for example, through a network or directly through an interface.

[0084] While in the embodiments of Figures 1-7, processor device 108 is depicted as a discrete device coupled to lidar system 106, in other examples, processor device 108 may be integral to lidar system 106. [0085] In operation, system 100 detects target object 102 with lidar system 106. Lidar system 106 directs light towards target object 102. Reflected light off of the target object 102 is received by lidar system 106. Lidar system 106 transmits received lightcurve data to processor device 108 for subsequent analysis. Processor device 108 may locate retroreflectors 104 present in the received data (for example, as shown in Figures 3A-3C). Additionally, processor device 108 may determine the distance between lidar system 106 and target object 102 for length and distance calibration. For example, it may be determined that the target object 102 is 10 kilometers away from the lidar system 106.

[0086] Next, processor device 108 may identify the retroreflector arrangement present in the captured lidar data by comparing the visible retroreflector pattern to retroreflector database 116 data. The identified retroreflector arrangement may be associated with a known target object and surface and may comprise a known length.

[0087] In some examples, processor device 108 may measure the length of the detected retroreflector arrangement and assign the known length to the retroreflector arrangement.

[0088] Next, the processor device 108 may detect the angle of the retroreflector arrangement relative to the lidar system using a pose estimation algorithm known in the art.

[0089] The angle and length of the retroreflector arrangement may be determined, determining the pose of the target object 102 to which the arrangement is coupled.

[0090] In some examples, multiple retroreflector arrangements may be present in the light curve. Each retroreflector arrangement may be associated with a different axis. In some examples, such arrangements may be orthogonal to one another. By differentiating multiple retroreflector signals, the rotation of the target object 102 about two axes may be determined.

[0091] Referring now to Figure 8, pictured therein is a method 300 of operating system 100 described herein, according to an embodiment. Method 300 comprises 302, 304 and 306. [0092] At 302, the object is detected with a lidar system from a distance, producing captured lidar data.

[0093] At 304, captured lidar data is processed to identify retroreflector arrangement by comparing the retroreflector arrangement to a retroreflector arrangement database.

[0094] At 306, object information such as pose is determined by applying an estimation algorithm, including a pose estimation algorithm, to the identified retroreflector arrangement.

[0095] 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 system for determining information of a target object, the system comprising: a plurality of retroreflectors on the target object; a lidar system for detecting a light curve of a pulse reflected from the object from a distance to produce captured lidar data; and a processor device comprising a memory and processor, the processor device configured to: process the captured lidar data to identify a retroreflector arrangement by comparing the retroreflector arrangement to a retroreflector arrangement database; and determine object information by applying an estimation algorithm to the identified retroreflector arrangement.

2. The system of claim 1 , wherein the object information includes pose, and wherein the estimation algorithm is a pose estimation algorithm.

3. The system of claim 2, wherein the object information includes a spacecraft identification code, and wherein the estimation algorithm is a spacecraft identification algorithm.

4. The system of claim 1 , wherein the target object includes a pattern that includes a linear array of retroreflectors.

5. The system of claim 4, wherein the pattern comprises two orthogonal linear arrays of retroreflectors.

6. The system of claim 1 , wherein the target object is detected with a single lidar reflection.

7. The system of claim 1 , wherein the target object is a spacecraft.

8. The system of claim 1 , wherein a spacing of each retroreflector arrangement includes a unique pattern that aligns with a known arrangement within the retroreflector arrangement database, such that each retroreflector arrangement is identified.

9. The method of claim 8, wherein each retroreflector arrangement is associated with a certain face, surface and/or axis of a specific target object.

10. The system of claim 1 , wherein the pose about two axes is determined.

11. A method for determining information of a target object, the target object includes a plurality of retroreflectors placed on the target object, the method comprising: detecting a light curve of a pulse reflected from the target object with a lidar system from a distance to produce captured lidar data; processing the captured lidar data to identify a retroreflector arrangement by comparing the retroreflector arrangement to a retroreflector arrangement database; and determining object information by applying an estimation algorithm to the identified retroreflector arrangement.

12. The method of claim 11 , wherein the object information includes pose, and wherein the estimation algorithm is a pose estimation algorithm.

13. The method of claim 11 , wherein the object information includes a spacecraft identification code, and wherein the estimation algorithm is a spacecraft identification algorithm.

14. The method of claim 11 , wherein the target object includes a pattern that includes a linear array of retroreflectors.

15. The method of claim 14, wherein the pattern comprises two orthogonal linear arrays of retroreflectors.

16. The method of claim 11 , wherein the target object is detected with a single lidar reflection.

17. The method of claim 11 , wherein the target object is a spacecraft.

18. The method of claim 11 , wherein a spacing of each retroreflector arrangement includes a unique pattern that aligns with a known arrangement within the retroreflector arrangement database, such that each retroreflector arrangement is identified.

19. The method of claim 18, wherein each retroreflector arrangement is associated with a certain face, surface and/or axis of a specific target object.

20. The method of claim 11 , wherein the pose about two axis is determined.