Description: For NASA missions requiring active control of segmented mirrors, optical trusses and booms, coherent, laser-based approaches such as CW laser interferometers have been preferred because they can provide very high resolution relative position measurements. Other approaches, such as multi-color interferometers can provide absolute range measurements. However, neither technique can measure multiple retroreflectors with a single optical transceiver. This has led to complex distributed metrology systems, which are limited in usefulness. Bridger Photonics Inc. proposes to investigate a novel distributed metrology approach that is uniquely enabled by its SLM-Series of actively stabilized swept laser sources. The technique, termed multi-point trilateration, uses a frequency modulated continuous wave (FMCW) chirped laser radar to determine the range to multiple reflectors that are illuminated simultaneously by three or more large field-of-view transceivers. Because Bridger's laser radar system can unambiguously determine the range to multiple targets within the field-of-view with high accuracy, trilateration can be utilized to estimate the three-dimensional (3D) coordinates for all of the retroreflective targets within the field-of-view. Bridger provides two critical advantages for the development of this distributed metrology system: 1) The world's highest resolution laser radar system, which is crucial for determining the range to the multiple retroreflectors, and 2) Proprietary processing techniques that enable Cramer-Rao lower bound limited range estimation. Under the proposed work plan, Bridger will provide an optimal design for Transceiver/Retroreflector geometries and model the expected performance, conduct demonstrations validating the system performance and provide a space-qualifiable, compact system design that can be built and delivered to NASA during a Phase II effort should the approach be feasible.

Benefits: Bridger Photonics Inc.'s frequency-modulated continuous wave (FMCW) ladar technology is relatively low cost, can be completely fiber based, and can operate over a broad range of wavelengths. Therefore it can enable a variety of interesting applications in both Government and commercial sectors including: 1) Flexible resolution systems with centimeter to nanometer accuracies for short and medium range chirped laser radar. Applications include autonomous aircraft and vehicle navigation, and object identification. The high sensitivity has interested US Navy customers with classified targets. 2) Bridger Photonics is working with the US Navy - NAVAIR to utilize the highly linear frequency sweeps to enable a non-mechanical, moderate range resolution (mm), real-time three-dimensional scanning laser radar system. This support tool will be utilized as an enhanced navigation aid during helicopter landings during low-visibility such as in brown-outs or in fog. The system also has the capability to warn pilots of small features such as wires or other fine obstacles. 3) Bridger has experienced extensive commercial interest for industrial metrology and machine vision ranging from the calibration of coordinate measuring machines to the inspection of parts and components for quality control.

The main target application for NASA is to utilize this multi-point trilateration system to monitor and control the length of critical supporting mechanisms associated with deployable space structures such as extremely large, segmented primary mirrors, trusses and booms for secondary optics and mission scientific instruments. Such deployable space structures are being considered for deployment such as the Advanced Technology Large Aperture Space Telescope (ATLAST). However, a variety of other space missions could benefit from highly distributed 3D coordinate estimation. For example, satellite to satellite position monitoring could be performed, or the system could be utilized for tracking positional state vectors for synthetic aperture radar interferometry. Given a suitable reference satellite, the system could also be utilized to provide accurate reference positions and attitudes for other satellites. The flexible resolution laser radar system itself also has applications in autonomous navigation and could be utilized to position and fly a variety of sensors, on UAVs, planes or robotic drones in space or to control swarms of satellites. It could also be utilized during docking maneuvers between manned and unmanned space vehicles and would be especially useful when extremely fine accuracies are required. 3D imagers based upon the same core technology could also aid in imaging of unidentified space debris and examining spacecraft for damage.