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A proposed laser-based instrument would quickly measure the approximate distance and approximate direction to the closest target within its field of view. The instrument would not contain any moving parts and its mode of operation would not entail scanning over of its field of view. Typically, the instrument would be used to locate a target at a distance on the order of meters to kilometers. The instrument would be best suited for use in an uncluttered setting in which the target is the only or, at worst, the closest object in the vicinity; for example, it could be used aboard an aircraft to detect and track another aircraft flying nearby. The proposed instrument would include a conventional time-of-flight or echo-phase-shift laser range finder, but unlike most other range finders, this one would not generate a narrow cylindrical laser beam; instead, it would generate a conical laser beam spanning the field of view. The instrument would also include a quadrant detector, optics to focus the light returning from the target onto the quadrant detector, and circuitry to synchronize the acquisition of the quadrant-detector output with the arrival of laser light returning from the nearest target. A quadrant detector constantly gathers information from the entire field of view, without scanning; its output is a direct measure of the position of the target-return light spot on the focal plane and is thus a measure of the direction to the target. The instrument should be able to operate at a repetition rate high enough to enable it to track a rapidly moving target. Of course, a target that is not sufficiently reflective could not be located by this instrument. Preferably, retroreflectors should be attached to the target to make it sufficiently reflective.

A proposed video guidance sensor (VGS) would be based mostly on the hardware and software of a prior Advanced VGS (AVGS), with some additions to enable it to function as a time-of-flight rangefinder (in contradistinction to a triangulation or image-processing rangefinder). It would typically be used at distances of the order of 2 or 3 kilometers, where a typical target would appear in a video image as a single blob, making it possible to extract the direction to the target (but not the orientation of the target or the distance to the target) from a video image of light reflected from the target. As described in several previous NASA Tech Briefs articles, an AVGS system is an optoelectronic system that provides guidance for automated docking of two vehicles. In the original application, the two vehicles are spacecraft, but the basic principles of design and operation of the system are applicable to aircraft, robots, objects maneuvered by cranes, or other objects that may be required to be aligned and brought together automatically or under remote control. In a prior AVGS system of the type upon which the now-proposed VGS is largely based, the tracked vehicle is equipped with one or more passive targets that reflect light from one or more continuous-wave laser diode(s) on the tracking vehicle, a video camera on the tracking vehicle acquires images of the targets in the reflected laser light, the video images are digitized, and the image data are processed to obtain the direction to the target. The design concept of the proposed VGS does not call for any memory or processor hardware beyond that already present in the prior AVGS, but does call for some additional hardware and some additional software. It also calls for assignment of some additional tasks to two subsystems that are parts of the prior VGS: a field-programmable gate array (FPGA) that generates timing and control signals, and a digital signal processor (DSP) that processes the digitized video images. The additional timing and control signals generated by the FPGA would cause the VGS to alternate between an imaging (direction-finding) mode and a time-of-flight (range-finding mode) and would govern operation in the range-finding mode.

Embedded software has been developed specifically for controlling an Advanced Video Guidance Sensor (AVGS). A Video Guidance Sensor is an optoelectronic system that provides guidance for automated docking of two vehicles. Such a system includes pulsed laser diodes and a video camera, the output of which is digitized. From the positions of digitized target images and known geometric relationships, the relative position and orientation of the vehicles are computed. The present software consists of two subprograms running in two processors that are parts of the AVGS. The subprogram in the first processor receives commands from an external source, checks the commands for correctness, performs commanded non-image-data-processing control functions, and sends image data processing parts of commands to the second processor. The subprogram in the second processor processes image data as commanded. Upon power-up, the software performs basic tests of functionality, then effects a transition to a standby mode. When a command is received, the software goes into one of several operational modes (e.g. acquisition or tracking). The software then returns, to the external source, the data appropriate to the command.

A video guidance sensor system for use, p.g., in automated docking of a chase vehicle with a target vehicle. The system includes an integrated rangefinder sub-system that uses time of flight measurements to measure range. The rangefinder sub-system includes a pair of matched photodetectors for respectively detecting an output laser beam and return laser beam, a buffer memory for storing the photodetector outputs, and a digitizer connected to the buffer memory and including dual amplifiers and analog-to-digital converters. A digital signal processor processes the digitized output to produce a range measurement.

A method is provided for controlling operations in a video guidance sensor system wherein images of laser output signals transmitted by the system and returned from a target are captured and processed by the system to produce data used in tracking of the target. Six modes of operation are provided as follows: (i) a reset mode; (ii) a diagnostic mode; (iii) a standby mode; (iv) an acquisition mode; (v) a tracking mode; and (vi) a spot mode wherein captured images of returned laser signals are processed to produce data for all spots found in the image. The method provides for automatic transition to the standby mode from the reset mode after integrity checks are performed and from the diagnostic mode to the reset mode after diagnostic operations are carried out. Further, acceptance of reset and diagnostic commands is permitted only when the system is in the standby mode. The method also provides for automatic transition from the acquisition mode to the tracking mode when an acceptable target is found.

The Advanced Video Guidance Sensor (AVGS), an active sensor system that provides near-range 6-degree-of-freedom sensor data, has been developed as part of an automatic rendezvous and docking system for the Demonstration of Autonomous Rendezvous Technology (DART). The sensor determines the relative positions and attitudes between the active sensor and the passive target at ranges up to 300 meters. The AVGS uses laser diodes to illuminate retro-reflectors in the target, a solid-state imager to detect the light returned from the target, and image capture electronics and a digital signal processor to convert the video information into the relative positions and attitudes. The development of the sensor, through initial prototypes, final prototypes, and three flight units, has required a great deal of testing at every phase, and the different types of testing, their effectiveness, and their results, are presented in this paper, focusing on the testing of the flight units. Testing has improved the sensor's performance.

A method and system for processing an image including capturing an image and storing the image as image pixel data. Each image pixel datum is stored in a respective memory location having a corresponding address. Threshold pixel data is selected from the image pixel data and linear spot segments are identified from the threshold pixel data selected.. Ihe positions of only a first pixel and a last pixel for each linear segment are saved. Movement of one or more objects are tracked by comparing the positions of fust and last pixels of a linear segment present in the captured image with respective first and last pixel positions in subsequent captured images. Alternatively, additional data for each linear data segment is saved such as sum of pixels and the weighted sum of pixels i.e., each threshold pixel value is multiplied by that pixel's x-location).

The Video Guidance Sensor (VGS) system is an optoelectronic sensor that provides automated guidance between two vehicles. In the original intended application, the two vehicles would be spacecraft docking together, but the basic principles of design and operation of the sensor are applicable to aircraft, robots, vehicles, or other objects that may be required to be aligned for docking, assembly, resupply, or precise separation. The system includes a sensor head containing a monochrome charge-coupled- device video camera and pulsed laser diodes mounted on the tracking vehicle, and passive reflective targets on the tracked vehicle. The lasers illuminate the targets, and the resulting video images of the targets are digitized. Then, from the positions of the digitized target images and known geometric relationships among the targets, the relative position and orientation of the vehicles are computed. As described thus far, the VGS system is based on the same principles as those of the system described in "Improved Video Sensor System for Guidance in Docking" (MFS-31150), NASA Tech Briefs, Vol. 21, No. 4 (April 1997), page 9a. However, the two systems differ in the details of design and operation. The VGS system is designed to operate with the target completely visible within a relative-azimuth range of +/-10.5deg and a relative-elevation range of +/-8deg. The VGS acquires and tracks the target within that field of view at any distance from 1.0 to 110 m and at any relative roll, pitch, and/or yaw angle within +/-10deg. The VGS produces sets of distance and relative-orientation data at a repetition rate of 5 Hz. The software of this system also accommodates the simultaneous operation of two sensors for redundancy

Four updated video guidance sensor (VGS) systems have been proposed. As described in a previous NASA Tech Briefs article, a VGS system is an optoelectronic system that provides guidance for automated docking of two vehicles. The VGS provides relative position and attitude (6-DOF) information between the VGS and its target. In the original intended application, the two vehicles would be spacecraft, but the basic principles of design and operation of the system are applicable to aircraft, robots, objects maneuvered by cranes, or other objects that may be required to be aligned and brought together automatically or under remote control. In the first two of the four VGS systems as now proposed, the tracked vehicle would include active targets that would light up on command from the tracking vehicle, and a video camera on the tracking vehicle would be synchronized with, and would acquire images of, the active targets. The video camera would also acquire background images during the periods between target illuminations. The images would be digitized and the background images would be subtracted from the illuminated-target images. Then the position and orientation of the tracked vehicle relative to the tracking vehicle would be computed from the known geometric relationships among the positions of the targets in the image, the positions of the targets relative to each other and to the rest of the tracked vehicle, and the position and orientation of the video camera relative to the rest of the tracking vehicle. The major difference between the first two proposed systems and prior active-target VGS systems lies in the techniques for synchronizing the flashing of the active targets with the digitization and processing of image data. In the prior active-target VGS systems, synchronization was effected, variously, by use of either a wire connection or the Global Positioning System (GPS). In three of the proposed VGS systems, the synchronizing signal would be generated on, and transmitted from, the tracking vehicle. In the first proposed VGS system, the tracking vehicle would transmit a pulse of light. Upon reception of the pulse, circuitry on the tracked vehicle would activate the target lights. During the pulse, the target image acquired by the camera would be digitized. When the pulse was turned off, the target lights would be turned off and the background video image would be digitized. The second proposed system would function similarly to the first proposed system, except that the transmitted synchronizing signal would be a radio pulse instead of a light pulse. In this system, the signal receptor would be a rectifying antenna. If the signal contained sufficient power, the output of the rectifying antenna could be used to activate the target lights, making it unnecessary to include a battery or other power supply for the targets on the tracked vehicle.

NASA's Marshall Space Flight Center was the driving force behind the development of the Advanced Video Guidance Sensor, an active sensor system that provides near-range sensor data as part of an automatic rendezvous and docking system. The sensor determines the relative positions and attitudes between the active sensor and the passive target at ranges up to 300 meters. The VGS uses laser diodes to illuminate retro-reflectors in the target, a solid-state camera to detect the return from the target, and image capture electronics and a digital signal processor to convert the video information into the relative positions and attitudes. This development effort has required a great deal of testing of various sorts at every phase of development, and some of the test efforts, predictions, and results will be laid out in this paper.

NASA's Marshall Space Flight Center was the driving force behind the development of the Advanced Video Guidance Sensor, an active sensor system that provides near-range sensor data as part of an automatic rendezvous and docking system. The sensor determines the relative positions and attitudes between the active sensor and the passive target at ranges up to 300 meters. The AVGS uses laser diodes to illuminate retro-reflectors in the target, a solid-state camera to detect the return from the target, and image capture electronics and a digital signal processor to convert the video information into the relative positions and attitudes. The AVGS will fly as part of the Demonstration of Autonomous Rendezvous Technologies (DART) in October, 2004. This development effort has required a great deal of testing of various sorts at every phase of development. Some of the test efforts included optical characterization of performance with the intended target, thermal vacuum testing, performance tests in long range vacuum facilities, EMI/EMC tests, and performance testing in dynamic situations. The sensor has been shown to track a target at ranges of up to 300 meters, both in vacuum and ambient conditions, to survive and operate during the thermal vacuum cycling specific to the DART mission, to handle EM1 well, and to perform well in dynamic situations.

This paper describes the current developments in video-based sensors at the Marshall Space Flight Center. The Advanced Video Guidance Sensor is the latest in a line of video-based sensors designed for use in automated docking systems. The X-33, X-34, X-38, and X-40 are all designed to be unpiloted vehicles; such vehicles will require a sensor system that will provide adequate data for the vehicle to accomplish its mission. One of the primary tasks planned for re-usable launch vehicles is to resupply the space station. In order to approach the space station in a self-guided manner, the vehicle must have a reliable and accurate sensor system to provide relative position and attitude information between the vehicle and the space station. The Advanced Video Guidance Sensor is being designed and built to meet this requirement, as well as requirements for other vehicles docking to a variety of target spacecraft. The Advanced Video Guidance Sensor is being designed to allow range and bearing information to be measured at ranges up to 2 km. The sensor will measure 6-degree-of-freedom information (relative positions and attitudes) from approximately 40 meters all the way in to final contact (approximately 1 meter range). The sensor will have a data output rate of 20 Hz during tracking mode, and will be able to acquire a target within one half of a second. The prototype of the sensor will be near completion at the time of the conference.

NASA's Marshall Space Flight Center (MSFC) has, for the last ten years, developed various video-based sensors for use in automated docking systems. The latest generation of sensor will operate at rates of up to 100 Hz, determining the relative position (X, Y, and Z) and attitude (Roll, Pitch, and Yaw) between the sensor and a small 3-dimensional target, making it suitable for applications in robotic sensing. The Advanced Video Guidance Sensor (AVGS) is designed to track multiple targets at different ranges and determine the position and attitude of each one. The previous generation of video sensor, the Video Guidance Sensor (VGS), was flown twice on the Space Shuttle to test its performance on orbit. One of the tests performed was determining the relative positions and attitudes between the VGS and its target, which was moved to various positions using the Remote Manipulator System (RMS). The RMS position data and VGS measured data were analyzed after the flights, with good correlation between the position and attitude data of the two data sets. The test using the RMS gives a good idea of the ability of the use of the AVGS as a sensor for end-effector position and attitude determination.

A synchronized target subsystem for use in an automated docking or station keeping system for docking a chase vehicle with a target vehicle wherein the chase vehicle is provided with a video camera which provides adjacent frames each having a predetermined time duration. A light source mounted on the target vehicle flashes at a frequency which has a time duration which is a multiple of the duration time of the frames, the light being on for at least one frame duration and being off for the remainder of the cycle. An image processing unit is connected to the camera for receiving signals from the camera and subtracting one of the adjacent frames from the other to detect whether the light appears in one frame, both frames or neither frame. If the target light appears in both frames or neither frame, the image processing unit feeds a signal to a timing circuit to advance the video camera one frame. This process is continued until the target light appears in one frame and not in the other, at which time the process of advancing the video camera is stopped.

Video-Based Sensor for Tracking 3-Dimensional Targets The National Aeronautics and Space Administration's (NASAs) Marshall Space Flight Center (MSFC) has been developing and testing video-based sensors for automated spacecraft guidance for several years, and the next generation of video sensor will have tracking rates up to 100 Hz and will be able to track multiple reflectors and targets. The Video Guidance Sensor (VGS) developed over the past several years has performed well in testing and met the objective of being used as the terminal guidance sensor for an automated rendezvous and capture system. The first VGS was successfully tested in closed-loop 3-degree-of-freedom (3- DOF) tests in 1989 and then in 6-DOF open-loop tests in 1992 and closed-loop tests in 1993-4. Development and testing continued, and in 1995 approval was given to test the VGS in an experiment on the Space Shuttle. The VGS flew in 1997 and in 1998, performing well for both flights. During the development and testing before, during, and after the flight experiments, numerous areas for improvement were found. The VGS was developed with a sensor head and an electronics box, connected by cables. The VGS was used in conjunction with a target that had wavelength-filtered retro-reflectors in a specific pattern, The sensor head contained the laser diodes, video camera, and heaters and coolers. The electronics box contained a frame grabber, image processor, the electronics to control the components in the sensor head, the communications electronics, and the power supply. The system works by sequentially firing two different wavelengths of laser diodes at the target and processing the two images. Since the target only reflects one wavelength, it shows up well in one image and not at all in the other. Because the target's dimensions are known, the relative positions and attitudes of the target and the sensor can be computed from the spots reflected from the target. The system was designed to work from I meter out to I 10 meters. The VGS was mounted on the Space Shuttle while its target was mounted on the Spartan free-flyer carried on the same Shuttle flight. The VGS tracked the Spartan at ranges up to 170m, and the VGS range data very closely matched the range data from the Hand-Held Laser- Rangefinder used by the astronauts on board the Shuttle. While the VGS was designed primarily as a terminal guidance sensor for an automated spacecraft, it could be applied to other uses. It could be used as an alignment aid for an operator of a remote system (giving position and attitude feedback data, as well as a camera view of the target), as a feedback system for a robotic arm, or for automated vehicle guidance. The next generation VGS, with its higher tracking rates, smaller size, and lower power could be used in more places than the original VGS, and by using LED's instead of laser diodes, the system would be eye-safe at any range. Other possible uses include tracking 3-dimensional objects with retro-reflectors mounted at various locations or motion analysis by placing several retro-reflectors on the moving object and tracking them at high speeds. There are few sensors capable of performing tasks similar to those the VGS can perform, and the next generation VGS will be even more capable than the original. Some of this work is previously presented in the papers.

Engineers at the Marshall Space Flight Center (MSFC) have been developing and testing video-based sensors for automated spacecraft guidance for several years. The next generation of Video Guidance Sensor (VGS) is being designed to be faster and more capable than ever. It will have applications to relative position measurement in any field of endeavor. The system works by sequentially firing two different wavelengths of laser diodes at the target (which has retroreflectors) and processing the two images. Since the target only reflects one wavelength, it shows up well in one image and not at all in the other. Because the target's dimensions are known, the relative positions and attitudes of the target and the sensor can be computed from the spots reflected from the target. The current sensor operates at 5 Hz at ranges from 1 to 110 meters with a 20 deg. field-of-view. The Video Guidance Sensor (VGS) developed over the past several years has performed well in testing and met the objective of being used as the terminal guidance sensor for an automated rendezvous and capture system. The first VGS was successfully tested in closed-loop 3-degree-of-freedom (3-DOF) tests in 1989 and then in 6-DOF open-loop tests in 1992 and closed-loop tests in 1993-4. Development and testing continued, and in 1995 approval was given to test the VGS in an experiment on the Space Shuttle. The VGS flew in 1997 and in 1998, performing well during both flight experiments. During the development and testing before, during, and after the flight experiments, numerous areas for improvement were found. The next generation of VGS is being designed to operate at up to 100 Hz tracking rates and at ranges from 0.5 to 200 meters. In addition to its use as a spacecraft guidance sensor, it could be used as an alignment aid for an operator of a remote system (giving position and attitude feedback data), as a feedback system for a robotic arm, or for automated vehicle guidance. The next generation VGS, with its higher tracking rates, smaller size, and lower power could be used in more places than the original VGS, and by using LED's instead of laser diodes, the system would be eye-safe at any range. More potential applications include aerial station keeping (keeping 2 or more autonomous aircraft within particular relative positions), under-water robotics, and the guidance of ground vehicles in predefined areas equipped with sets of targets.

The Video Guidance Sensor (VGS) flew on Shuttle mission STS-95 in October of 1998 to test the VGS functional characteristics on orbit. This was the second flight of the VGS, and during these two flights, both long range and short range data were gathered under a variety of lighting conditions, orbital exposure times, and temperatures. The flight experiment sensor was designed to operate from 1.5 meter range out to 110 meter range, with a field-of-view of 16 X 21 degrees. The VGS tracked its target at a 5 Hz rate and returned 6-degree-of-freedom information on the target's position and attitude relative to the sensor. The VGS was mounted in the Shuttle cargo bay, and its target was mounted on the Spartan spacecraft being carried on this mission. The VGS is a sensor designed to allow an automated vehicle to dock with a spacecraft equipped with a passive target. The VGS is a part of an Automated Rendezvous and Capture (AR&C) system being developed and tested by NASA. The orbital testing included operations with the target on the Shuttle's Remote Manipulator System (RMS) near the start of each flight of the VGS, long-range data (on the STS-95 flight) during the Shuttle rendezvous with the Spartan two days later, and some more RMS operations later in the mission. The data returned from the orbital testing included VGS diagnostics, acquisition, and tracking data, RMS positions, hand-held laser range data, tapes of the data from the VGS video camera, and orbital positioning data from the Spartan and the Shuttle to allow correlation of the VGS data with orbital best-estimate-of-truth data. The Video Guidance Sensor performed well in all phases of the testing, and the VGS is being incorporated into the ground testing of a complete automated rendezvous and docking system. Work on the development of the next generation VGS is continuing.

NASA's Marshall Space Flight Center flew on the STS-87 mission an active sensor system, the Video Guidance Sensor (VGS), to demonstrate its functioning in space and to collect performance data. The VGS was designed to provide near-range sensor data as part of an automatic rendezvous and docking system. The sensor determines the relative positions and attitudes between the active sensor and the passive target. The VGS uses laser diodes to illuminate retro-reflectors in the target, a solid-state camera to detect the return from the target, and a frame grabber and digital signal processor to convert the video information into the relative positions and attitudes. The system is designed to operate with the target within a relative azimuth of +/- 9.5 degrees and a relative elevation of +/- 7.5 degrees. The system will acquire and track the target within that field-of-view anywhere from 1.5 meters to 110 meters range, and is designed to acquire at relative attitudes of +/- 10 degrees in pitch and yaw and at any roll angle. The data is output from the sensor at 5 Hz, and the target and sensor software have been designed to permit two independent sensors to operate simultaneously (in order to allow for redundancy). The data from the flight experiment includes raw video data from the VGS camera, relative position and attitude measurements from the VGS to the target, independent hand-held laser ranges from the Shuttle Aft Flight Deck to the target, and Remote Manipulator System position data to correlate with the VGS data. The experiment was quite successful and returned much useful information. The experience gained from the design and flight of this experiment will lead to improved video sensors in the future.

A Global Positioning System Synchronized Active Light Autonomous Docking System (GPSSALADS) for automatically docking a chase vehicle with a target vehicle comprising at least one active light emitting target which is operatively attached to the target vehicle. The target includes a three-dimensional array of concomitantly flashing lights which flash at a controlled common frequency. The GPSSALADS further comprises a visual tracking sensor operatively attached to the chase vehicle for detecting and tracking the target vehicle. Its performance is synchronized with the flash frequency of the lights by a synchronization means which is comprised of first and second internal clocks operatively connected to the active light target and visual tracking sensor, respectively, for providing timing control signals thereto, respectively. The synchronization means further includes first and second Global Positioning System receivers operatively connected to the first and second internal clocks, respectively, for repeatedly providing simultaneous synchronization pulses to the internal clocks, respectively. In addition, the GPSSALADS includes a docking process controller means which is operatively attached to the chase vehicle and is responsive to the visual tracking sensor for producing commands for the guidance and propulsion system of the chase vehicle.

Proposed optoelectronic system for guiding vehicle in approaching and docking with another vehicle includes active optical targets (flashing lights) on approached vehicle synchronized with sensor and image-processing circuitry on approaching vehicle. Conceived for use in automated approach and docking of two spacecraft. Also applicable on Earth to manually controlled and automated approach and docking of land vehicles, aircraft, boats, and submersible vehicles, using GPS or terrestrial broadcast time signals for synchronization. Principal advantage: optical power reduced, with consequent enhancement of safety.

The Automated Rendezvous and Docking system (ARAD) is composed of two parts. The first part is the sensor which consists of a video camera ringed with two wavelengths of laser diode. The second part is a standard Remote Manipulator System (RMS) target used on the Orbiter that has been modified with three circular pieces of retro-reflective tape covered by optical filters which correspond to one of the wavelengths of laser diode. The sensor is on the chase vehicle and the target is on the target vehicle. The ARAD system works by pulsing one wavelength laser diodes and taking a picture. Then the second wavelength laser diodes are pulsed and a second picture is taken. One picture is subtracted from the other and the resultant picture is thresholded. All adjacent pixels above threshold are blobbed together (X and Y centroids calculated). All blob centroids are checked to recognize the target out of noise. Then the three target spots are windowed and tracked. The three target spot centroids are used to evaluate the roll, yaw, pitch, range, azimuth, and elevation. From that a guidance routine can guide the chase vehicle to dock with the target vehicle with the correct orientation.

NASA Marshall Space Flight Center (MSFC) has developed and tested an engineering model of an automated rendezvous and docking sensor system composed of a video camera ringed with laser diodes at two wavelengths and a standard remote manipulator system target that has been modified with retro-reflective tape and 830 and 780 mm optical filters. TRW has provided additional engineering analysis, design, and manufacturing support, resulting in a robust, low cost, automated rendezvous and docking sensor design. We have addressed the issue of space qualification using off-the-shelf hardware components. We have also addressed the performance problems of increased signal to noise ratio, increased range, increased frame rate, graceful degradation through component redundancy, and improved range calibration. Next year, we will build a breadboard of this sensor. The phenomenology of the background scene of a target vehicle as viewed against earth and space backgrounds under various lighting conditions will be simulated using the TRW Dynamic Scene Generator Facility (DSGF). Solar illumination angles of the target vehicle and candidate docking target ranging from eclipse to full sun will be explored. The sensor will be transportable for testing at the MSFC Flight Robotics Laboratory (EB24) using the Dynamic Overhead Telerobotic Simulator (DOTS).

A video-based sensor has been developed specifically for the close-range maneuvering required in the last phase of autonomous rendezvous and capture. The system is a combination of target and sensor, with the target being a modified version of the standard target used by the astronauts with the Remote Manipulator System (RMS). The system, as currently configured, works well for autonomous docking maneuvers from approximately forty feet in to soft-docking and capture. The sensor was developed specifically to track and calculate its position and attitude relative to a target consisting of three retro-reflective spots, equally spaced, with the center spot being on a pole. This target configuration was chosen for its sensitivity to small amounts of relative pitch and yaw and because it could be used with a small modification to the standard RMS target already in use by NASA.