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MARLI: Mars Lidar for Measuring Global Wind and Aerosol Profiles from Orbit

Presentation #317.04 in the session Future Missions and Instrumentations - Rocky Bodies, Atmospheres (Poster + Lightning Talk)

Published onOct 23, 2023
MARLI: Mars Lidar for Measuring Global Wind and Aerosol Profiles from Orbit

NASA’s Mars Exploration NEX-SAG Group has identified atmospheric wind measurements as key science objective for a future Mars orbiter. Winds are key to understand atmospheric transport and answer fundamental questions about the CO2, H2O, and dust cycles of the Mars climate. Only few direct observations of Mars winds exist, which leaves many basic questions unanswered. NASA Goddard is developing the MARLI lidar [2,3] to measure the height-resolved wind and dust profiles continuously, day and night from orbit. This work has been supported by the NASA PICASSO and MatISSE Programs.

The MARLI lidar is designed to observe the atmosphere from a nominally circular polar orbit. The instrument is designed to be pointed ~30° off-nadir in a cross-track viewing direction. The lidar will continuously measure dust aerosol backscatter profiles, cross-polarized backscatter profiles and the component of the aerosol Doppler shift from wind profiles along the instrument’s line-of-sight.

The MARLI approach measures the height-resolved atmospheric characteristics along a single line-of-sight. MARLI utilizes a pulsed single-frequency Nd:YAG laser. The laser emits linearly polarized ~40 nsec wide pulses at a nominal 1 kHz pulse rate. The lidar receiver uses a ~50 cm diameter telescope and its optics split the returned signal into 3 paths. Two paths are used to illuminate a 5 cm diameter etalon at different angles that are then focused onto separate detector pixels. These elements are configured as a double-edge Doppler discriminator for the aerosol backscatter profiles. The receiver uses a photon-sensitive HgCdTe APD detector. The targeted instrument size is a ~70 cm cube with payload parameters of < 40 kg, < 90W, and ~50 kbits/sec.

The MARLI lidar will obtain atmospheric profile measurements at a rate of ≥ 2 Hz with 150 m vertical resolution. The measurement performance depends on the orbit altitude, the atmospheric vertical bin depth and averaging time. The vertical and time averaging will be performed on the ground, so are adjustable in analysis. We have calculated the expected performance using a lidar model [3] that which assumes averaging over 40 seconds (~2° latitude for a 400 km polar orbit) and 2 km thick vertical bins.

We have developed all components and demonstrated most aspects of the measurement with an instrument breadboard. A brassboard version of the lidar has been completed and is being used to demonstrate atmospheric measurements from our laboratory. Details of the instrument and its measurements will be shown.

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