The Johns Hopkins University Applied Physics Laboratory (APL) is developing a Terrain Relative Navigation (TRN) system using passive optical terrain sensing for lunar, asteroid and comet landing applications. APL has more than three decades expertise in developing visual-aided navigation techniques and is advancing previously developed technology to prototype the Autonomous Precision Landing Navigation (APLNav) TRN system. APLNav facilitates precision landing in illuminated conditions on celestial bodies without an atmosphere; including the low illumination conditions existing at the lunar poles. The APLNav system uses digital cameras to image the body's surface and correlates those images with on-board reference images. The NASA Autonomous Precision Landing and Hazard Avoidance Technology (ALHAT) program is developing a precision landing system capable of landing the Altair Lunar Descent Vehicle (LDV) on the moon with a landing accuracy of 90 m (3a). APL is working with ALHAT to modify APLNav for potential use on the Altair LDV and to bring this version of APLNav to Technology Readiness Level 6, system demonstration in a relevant environment, by 2011. This paper describes APL's current efforts to develop, analytically assess performance, and flight test, APLNav for use in the ALHAT application.
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