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6 May 2009Present and future space applications of photon-counting lidars
The first space application of photon-counting lidars occurred shortly after the landing of Apollo 11 on the
Moon. Various scientific groups used lasers to range to retroreflector panels left on the lunar surface by the
astronauts. Because of the great distances involved (384,000 km one-way) and practical limitations on laser
energy and telescope aperture, the detected signals were necessarily at the single photon level. The Lunar
Laser Ranging (LLR) effort has continued uninterrupted over the past four decades and has allowed
scientists to study solar system dynamics, Earth-lunar interactions, and lunar properties. It has also served
as a testbed for relativistic theories. Since the mid-1990's, the author has applied the photon-counting
technique to a number of new space applications. These include: (1) an eyesafe satellite laser ranging
system which presently tracks high altitude (6000 km) satellites with sub-cm precision at kHz rates with
only 60 microjoules of transmitted energy; (2) an airborne, high resolution 3D imaging lidar which operates
day or night and can be scaled to globally and contiguously map extraterrestrial moons from 100 km orbits;
(3) an upcoming NASA mission for mapping the Earth's surface in 3D from a 600 km orbit; and (4)
interplanetary ranging and time transfer via two-way laser transponders. The present paper provides an
overview of these efforts.
John J. Degnan
"Present and future space applications of photon-counting lidars", Proc. SPIE 7323, Laser Radar Technology and Applications XIV, 73230E (6 May 2009); https://doi.org/10.1117/12.817860
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John J. Degnan, "Present and future space applications of photon-counting lidars," Proc. SPIE 7323, Laser Radar Technology and Applications XIV, 73230E (6 May 2009); https://doi.org/10.1117/12.817860