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Proceedings Paper

Geoscience Laser Altimeter System (GLAS) spaceflight instrument fiber optic system
Author(s): Mark C. Flanegan
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Paper Abstract

GLAS is a satellite laser altimeter designed to measure ice- sheet topography and cloud and atmospheric properties. The onboard laser is an Nd:YAG with doubler, emitting 1064 nm and 532 nm light. The reflected light from the Earth and atmosphere is collected by a telescope and analyzed to produce the altimetry results. Fiber optics are used to route timing and calibration signals within the instrument as well as to provide calibrated delays. The fiber optic system includes free space to fiber coupling optics, cables and connectors, diode laser and LED fiber pigtails and a 2 kilometer fiber optic delay line. Since these signals are received and processed as analog values, it is necessary to preserve the magnitude, timing and pulse shape as much as possible in the thermal, mechanical and radiation environment of space. This is in contrast to many onboard fiber optic systems which are used for digital communication and can accept wide variations in these parameters as long as the thresholds for accurate detection of a bit aren't exceeded. The requirements include a stability of up to 1% in signal magnitude and 20 ps timing stability in the timing signals and fiber optic delay line over the whole mission, including all environmental effects. Meeting these requirements with the spacecraft resources available has proven challenging. Fiber optic components have been chosen and tested to accomplish this as best as possible. The system design, components selected and testing performed will be discussed in this paper.

Paper Details

Date Published: 2 February 2001
PDF: 7 pages
Proc. SPIE 4216, Optical Devices for Fiber Communication II, (2 February 2001); doi: 10.1117/12.414116
Show Author Affiliations
Mark C. Flanegan, NASA Goddard Space Flight Ctr. (United States)


Published in SPIE Proceedings Vol. 4216:
Optical Devices for Fiber Communication II
Dilip K. Paul; Michel J. F. Digonnet; Osman S. Gebizlioglu; Osman S. Gebizlioglu; Roger A. Greenwell; Roger A. Greenwell; Dennis N. Horwitz; Dennis N. Horwitz; Dilip K. Paul, Editor(s)

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