NASA Goddard - Laser Remote Sensing Branch 1/16/02 JBA 1 3/12/02 NASA/GSFC - Laser Remote Sensing Branch 1 Mars Orbital Lidar Small Orbital Planetary Lidar for Measurement of Water Vapor, Cloud and Aerosol Profiles James B. Abshire, Michael A. Krainak, Xiaoli Sun, Gary Duerksen*, Jonathan A. R. Rall R. Michael Hardesty**, Bruce Jakosky*** Code SL PIDDP RTOP, GSFC IR&D (ongoing) We are conducting R&D on a small orbital atmospheric lidar to measure water vapor and aerosol distributions for orbital planetary missions. Based on current NASA plans, a small orbital water- vapor lidar seems very well matched to the measurement needs of the Mars and exobiology programs. Our goal is to conduct the R&D on the new transmitter and receiver components and techniques needed to allow a successful proposal to the 2007 launch opportunity to Mars. Our lidar is well suited to the small Discovery-class orbiters in NASA’s planetary program plans. It will provide greatly needed global measurements of water-vapor profiles, water-vapor column and aerosol profiles around Mars or other planets. The lidar's primary purpose is to continuously profile the water vapor in the atmosphere from the Mars orbit in order to quantify its dynamics, its relationship to the dust distribution and to infer its exchange with the Mars surface. It will profile the Mars atmosphere with much higher vertical and spatial resolution than existing or planned measurements. The lidar's water vapor vertical resolution is 1 km and spatial resolution is approximately 1 degree. We calculate that it can determine a global map of the vertical distribution of Mars water vapor to 4 pr um (day) and 0.8 pr um (night) every 15 days. Even better determinations can be made by using spatial, temporal or vertical averaging. The column averaged water-vapor determinations use the strong surface echo pulses and permit measurements to better than 0.1 pr um per 1 deg. cell. The lidar's aerosol profiles have 200 m resolution. The lidar’s measurement of the depolarization of the atmospheric backscatter permits height resolved discrimination between atmospheric ice and dust. Our work will demonstrate that the all-diode transmitter can be developed with the quality, powers and efficiency needed for orbital measurements and the improved spectral sensitivity needed for the receiver. Our approach, using new diode-laser and electro-optic receiver technology, is innovative and enables a dramatically smaller lidar which is suitable for planetary atmospheric science investigations. By using different diode-laser wavelengths, our approach can be generalized to measure other trace gases from orbit or landers. Our proposed work addresses Mars atmospheric physics, laser technology, and will include laboratory R&D, breadboards and field demonstrations.

NASA Goddard - Laser Remote Sensing Branch 1/16/02 JBA 2 3/12/02 NASA/GSFC - Laser Remote Sensing Branch 2 Mars Orbital Lidar Instrument Size (conceptual) cm telescope - based on MOLA Mass ~ 60 kg Power ~ W (resolution dependant) Data rate ~ 10 Kbits/sec Size: roughly a cube 70x70 x70 cm Measurement techniques - basis Atmos. backscatter profiles - aircraft/GLAS WV measurements - PIDDP, aircraft work Ranging to surface - GLAS Precise pointing measurements - GLAS MOLA Instrument Mars Global Surveyor Mission Lidar for global monitoring of “Mars dynamics” Ie Seasonal variations in atmospheric dust, ice, H2O, and precise height of ice caps

NASA Goddard - Laser Remote Sensing Branch 1/16/02 JBA 3 3/12/02 NASA/GSFC - Laser Remote Sensing Branch 3 Mars Orbital Lidar Concept Schematic for WV channel

NASA Goddard - Laser Remote Sensing Branch 1/16/02 JBA 4 3/12/02 NASA/GSFC - Laser Remote Sensing Branch 4 Mars Orbital Lidar Key Instrument Technologies: Pulsed laser at 1064 and 532 nm - GLAS flight laser derivatives 935 nm transmitter for WV measurements: All diode laser (baseline) Diode laser seeded OPO, pumped by 532 nm 1580 nm laser- diode seed lasers with fiber amplifier (commercial) Receiver Telescope (Beryllium) - MOLA/CIRS Narrow filters, small tunable etalon - GLAS Sensitive photon counting detectors - GLAS

NASA Goddard - Laser Remote Sensing Branch 1/16/02 JBA 5 3/12/02 NASA/GSFC - Laser Remote Sensing Branch 5 Mars Orbital Lidar WV Laser transmitter Technology Diode Seed Lasers “Asymmetric cladding InGaAs-GaAs-AlGaAs ridge waveguide distributed Bragg reflector lasers with operating wavelengths of nm” Roh SD, Hughes JS, Lammert RM, Osowski ML, Beernink KJ, Papen GC, Coleman JJ. IEEE PHOTONICS TECHNOLOGY LETTERS 9: (3) MAR 1997 But these new lasers have independent grating tuning section

NASA Goddard - Laser Remote Sensing Branch 1/16/02 JBA 6 3/12/02 NASA/GSFC - Laser Remote Sensing Branch 6 Mars Orbital Lidar Water Vapor Absorption Line Scan

NASA Goddard - Laser Remote Sensing Branch 1/16/02 JBA 7 3/12/02 NASA/GSFC - Laser Remote Sensing Branch 7 Mars Orbital Lidar 935 nm - Semiconductor Optical amplifier Reference: “5-W 930 nm tunable external-cavity laser”, Hagberg, M.;O’Brien, S.; Hanmin Zhao; Lang, R. CLEO 98 Paper CMJ8 Pages W 935 nm flared amplifier

NASA Goddard - Laser Remote Sensing Branch 1/16/02 JBA 8 3/12/02 NASA/GSFC - Laser Remote Sensing Branch 8 Mars Orbital Lidar Status as of 3/02 Some planned R&D has been delayed by work on GLAS GLAS has space qualified the needed filters, etalons, photon counting detectors Telecom boom has changed the technology picture 935 diodes no longer avail Some key researchers left GSFC Large very capable technology base in fiber lasers Need to revisit approach, to address: Best technical approach today for WV measurements: Seeded OPO pumped by 532 nm ? Fiber amplifiers using raman gain ? Measuring atmospheric surface pressure - via laser sounder approach Add precise ranging (10 cm) to surface using 1064 nm pulses Will complete reassessment by 6/02