5 September 2000 Flight characterization of the NEAR Laser Rangefinder
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Abstract
On February 14, 2000, after a 4-year transit, the recently renamed Near-Earth Asteroid Rendezvous (NEAR) Shoemaker spacecraft entered a 300-km orbit around the asteroid 433 Eros. Onboard the spacecraft, the NEAR Laser Rangefinder facility instrument began operation providing high-resolution topographical profiles of Eros. Developed at the Johns Hopkins University Applied Physics Laboratory, the NLR is a bistatic, direct-detection laser altimeter. The transmitter uses a gallium arsenide diode-pumped Cr:Nd:YAG laser at 1.064 micrometer. This lithium-niobate Q-switched transmitter emits 15-ns pulses at 15.3 mJ/pulse (1/8 to 8 Hz), permitting reliable NLR operation at the required 50-km altitude. The separate receiver employs an extended infrared-sensitive avalanche-photodiode detector with a 7.62-cm clear aperture Dall-Kirkham collecting telescope. End-to-end calibration capability exists between the transmitter and receiver via a 109.5-m spooled fiber-optic. A fraction of each emitted outgoing laser pulse is sampled, optically delayed and injected into the receiver optics providing a 'fixed target' to the NLR. In preparation for sampling Eros, the NLR has been operated numerous times during the 4-year transit period. These 'post-launch tests' provided housekeeping and calibration data useful in characterization and verification of the NLR design. This article summarizes the design used, post-launch test results, and implementation details used to control the NLR illustrating the complexity of operating an instrument in deep space. Additionally, preliminary evaluation of NLR performance using preliminary altimetry data of 433 Eros is presented.
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Timothy D. Cole, Timothy D. Cole, Andrew F. Cheng, Andrew F. Cheng, R. Alan Reiter, R. Alan Reiter, David E. Smith, David E. Smith, Maria T. Zuber, Maria T. Zuber, } "Flight characterization of the NEAR Laser Rangefinder", Proc. SPIE 4035, Laser Radar Technology and Applications V, (5 September 2000); doi: 10.1117/12.397785; https://doi.org/10.1117/12.397785
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