Role of Lidar Technology in Future NASA Space Missions
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Role of Lidar Technology in Future NASA Space Missions Farzin Amzajerdian NASA Langley Research Center, MS 468, Hampton, VA, 23681 ABSTRACT The past success of lidar instruments in space combined with potentials of laser remote sensing techniques in improving measurements traditionally performed by other instrument technologies and in enabling new measurements have expanded the role of lidar technology in future NASA missions. Compared with passive optical and active radar/microwave instruments, lidar systems produce substantially more accurate and precise data without reliance on natural light sources and with much greater spatial resolution. NASA pursues lidar technology not only as science instruments, providing atmospherics and surface topography data of Earth and other solar system bodies, but also as viable guidance and navigation sensors for space vehicles. This paper summarizes the current NASA lidar missions and describes the lidar systems being considered for deployment in space in the near future. CURRENT SPACE-BASED LIDARS Presently, NASA has four major lidar instruments in space with another to be launched later this year. The ICESat (Ice, Cloud and land Elevation Satellite) and CALIPSO (CloudAerosol Lidar and Infrared Pathfinder Satellite Observation) are Earth science missions providing valuable atmospheric data and monitoring global climate changes [1-4]. The other three instruments are part of planetary missions: Mercury Laser Altimeter (MLA) as part of the MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) mission [5], Mars Meteorological Lidar onboard Phoenix Lander and Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar Reconnaissance Orbiter. Table 1 summarizes the high-level specifications of these instruments and their launch dates. All these instruments utilize diodepumped Nd:YAG laser as their transmitter source and incorporate some level of redundancy by using backup lasers to ensure long operational lifetime in space. Table 1. Current NASA Space-based Scientific Lidar Instruments. Mission
Lidar Instruments
Primary data Pulse Rep No. of Peak No. products Energy rate Pump Power/bar of Bars lasers 110 mJ 40 54 65-85 W 3 ICESat Laser Ice sheet (Earth Science) Altimeter w/ height, Clouds atm channel 50 W CALIPSO Atmospheric Clouds and 220 mJ 20 192 2 (Earth Science) Backscatter aerosol profiles Mercury 20 mJ 8 Surface Topography Mars Atmospheric Mars aerosol, 1 mJ 100 Backscatter Ice clouds
MESSENGER Phoenix Lander
Lunar Reconnaissance Orbiter
Laser Altimeter
Laser Altimeter
global lunar topographic model
2.7 mJ 28
10
4
100 W
70 W
Telescope Aperture Diameter 100 cm
Launch Required date Lifetime In Space January 3 12,2003
100 cm
April 28, 2006
3
1
11.5 cm X4
7
1
10 cm
August 3, 2004 3, 2004 August 4, 2007
2
14 cm
Late 2008
0.2 2
ICESat, CALIPSO and the Phoenix Meteorological Lidar instruments use external cavity doublers to generate 532-nm radiation along with the fundamental 1064-nm beam. The 532-nm beam profiles the atmospheri
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