In 1999 after a 3-year transit, the Near-Earth Asteroid Rendezvous (NEAR) spacecraft will enter a low-altitude (approximately 50 km) orbit about the asteroid, 433 Eros. Five instruments, including a laser radar, will operate continuously during the one-year orbit at Eros. The NEAR laser rangefinder (NLR), developed at the Applied Physics Laboratory (APL), is a robust rangefinder and the first spaceborne altimeter to have continuous inflight calibration capability. A bistatic configuration, the NLR uses a diode- pumped Cr:Nd:YAG transmitter and a leading-edge receiver with a 3.5-inch aperture Dall-Kirkham telescope. Detection is accomplished using an enhanced-silicon avalanche photodiode. From system tests, the NLR is capable of ranging in excess of 100 km to the asteroid's surface. Measurements of the time-of-flight between laser pulse firings and detection of surface backscatter are made using an APL- developed receiver having range resolution of 31.48 cm and accuracy of 2 m. Total mass of the NLR is 4.9 kg and its average power consumption is <EQ 15.1 W. This paper reviews specifications for the NLR instrument, provides overall design details, and presents system performance using prelaunch test results.

Date Published: 26 June 1996
PDF: 18 pages
Proc. SPIE 2748, Laser Radar Technology and Applications, (26 June 1996); doi: 10.1117/12.243547

Published in SPIE Proceedings Vol. 2748:
Laser Radar Technology and Applications
Gary W. Kamerman, Editor(s)