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Raman Airborne Spectroscopic Lidar


RASL was developed under the first NASA Instrument Incubator program. The first laboratory measurements with RASL were taken in September 2002. It is now being configured for aircraft flight. It is the first airborne lidar system to offer the combined measurements of water vapor mixing ratio, aerosol scattering ratio, aerosol backscattering coefficient, aerosol depolarization and liquid water mixing ratio.

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RASL uses a tripled Nd:YAG laser combined with a 24 inches Dall-Kirkham telescope to make all of its measurements using a single field of view. Photographs of the RASL telescope during its assembly and test are shown below. The RASL final report describes the history of the development of the lidar and shows the first test measurements of the new system.

RASL Specifications
Laser Continuum 9050Nd:YAG (355 nm), 350 mj/pulse, 50 Hz
Telescope Custom 24” athermal, manufactured by DFM Engineering
Data acquisition 250 Mhz photon counting and 20 Mhz analog detection
Range resolution 7.5 meter
Measurements [Molecule/Wavelength (nm)/Bandpass (nm)] water vapor/407.5/0.25
liquid water/403.2/6.0
oxygen/375/0.3 or CO2/371.6/0.3
elastic unpolarized/354.7/0.3
elastic parallel polarized/354.7/0.3
elastic perpendicular polarized/354.7/0.3
Detectors Hamamatsu R1924 (Raman) and R7400 (aerosol) PMTs
Field of View 0.25 mrad

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RASL Instrument Close-Up

Isometric view of current RASL design.
For scale reference, the telescope outer diameter is 28 inches.

Diagram of Raman Airborne Spectroscopic Lidar
Diagram of NASA GSFC's Raman Airborne Spectroscopic Lidar.
(Click on image for full view)

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Photo Gallery

RASL telescope
RASL telescope ready
for testing
RASL data acquisition electronics
RASL data acquisition

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Martin Cadirola, Ecotronics Digital Media
NASA Official:
Dr. David Whiteman,
Last Updated:
Friday, January 20, 2006

Go to Code 613.1 Raman Lidar Group home page