Lunar Descent Terrain Relative Navigation Using APLNav
- Paper number
IAC-08.A3.2.INT6
- Author
Mr. Dewey Adams, Johns Hopkins University Applied Physics Laboratory, United States
- Year
2008
- Abstract
The Johns Hopkins University Applied Physics Laboratory (APL) is developing a Terrain Relative Navigation (TRN) system using passive optical terrain sensing for precision 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 single or multiple digital cameras (depending on the application) to image the celestial body’s surface and correlates the sensed images with on board rendered reference images. The reference images are derived for the estimated inertial navigation state using an on board database composed of a Surface Reflectance Maps (SRM) and Digital Elevation Map (DEM) that define the surface. The maximum correlation value corresponds to the spacecraft location with respect to the terrain reference frame at the time the image was taken. This location is used to periodically correct the accumulated error in the spacecraft’s inertial navigation system. The NASA Autonomous Precision Landing and Hazard Avoidance Technology (ALHAT) program is developing an autonomous precision landing system capable of landing the Altair Lunar Descent Vehicle (LDV) on the moon with a landing accuracy of 90 m (3?). APL is working with ALHAT to modify a version of 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 2012. To demonstrate APLNav functionality, APL has prepared a prototype for use in an ALHAT sponsored field test using a helicopter as a test platform. In this test, imagery of a surveyed landscape at Death Valley National Park, California is over flown under specific lighting conditions with the APLNav determined state compared to a GPS state acting as the truth reference. This paper presents a description of the APLNav system; an analytical assessment of APLNav performance as applied to lunar descent and landing in low illumination conditions such as exist at Shackleton crater; and the results of helicopter platform field-testing. Also, APL is studying methods of augmenting an astronaut’s visual perception in low illumination conditions. This paper describes preliminary results of the investigation to assist an astronaut’s ability to identify landing site hazards in poorly illuminated conditions and to perform navigation tasks.
- Abstract document
- Manuscript document
IAC-08.A3.2.INT6.pdf (🔒 authorized access only).
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