NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Performance of the Lidar Design and Data Algorithms for the GLAS Global Cloud and Aerosol MeasurementsThe Geoscience Laser Altimeter System (GLAS) launched in early 2003 is the first polar orbiting satellite lidar. The instrument design includes high performance observations of the distribution and optical scattering cross sections of atmospheric clouds and aerosol. The backscatter lidar operates at two wavelengths, 532 and 1064 nm. For the atmospheric cloud and aerosol measurements, the 532 nm channel was designed for ultra high efficiency with solid state photon counting detectors and etalon filtering. Data processing algorithms were developed to calibrate and normalize the signals and produce global scale data products of the height distribution of cloud and aerosol layers and their optical depths and particulate scattering cross sections up to the limit of optical attenuation. The paper will concentrate on the effectiveness and limitations of the lidar channel design and data product algorithms. Both atmospheric receiver channels meet and exceed their design goals. Geiger Mode Avalanche Photodiode modules are used for the 532 nm signal. The operational experience is that some signal artifacts and non-linearity require correction in data processing. As with all photon counting detectors, a pulse-pile-up calibration is an important aspect of the measurement. Additional signal corrections were found to be necessary relating to correction of a saturation signal-run-on effect and also for daytime data, a small range dependent variation in the responsivity. It was possible to correct for these signal errors in data processing and achieve the requirement to accurately profile aerosol and cloud cross section down to 10-7 llm-sr. The analysis procedure employs a precise calibration against molecular scattering in the mid-stratosphere. The 1064 nm channel detection employs a high-speed analog APD for surface and atmospheric measurements where the detection sensitivity is limited by detector noise and is over an order of magnitude less than at 532 nm. A unique feature of the GLAS is a full acquisition of the surface return pulse, which has important application to the atmospheric transmission retrieval.
Document ID
20080039555
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Spinhirne, James D.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Palm, Stephen P.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Hlavka, Dennis L.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Hart, William D.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 24, 2013
Publication Date
July 22, 2007
Subject Category
Meteorology And Climatology
Meeting Information
Meeting: IGARSS 2007 Symposium
Location: Barcelona
Country: Spain
Start Date: July 22, 2007
End Date: July 28, 2007
Sponsors: Institute of Electrical and Electronics Engineers
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

Available Downloads

There are no available downloads for this record.
No Preview Available