Geoscience Laser Altimeter System - Laser Pickoff System

Time period

December 1998 to March 2001

Project description

The Laser Pickoff System couples laser light into optical detectors throughout the GLAS instrument for on-orbit calibrations. As the 1.18-inch (30-millimeter) square laser beam leaves the GLAS instrument for the earth's surface, the Laser Pickoff System routes 2% of the outgoing laser energy into six fiber optics that perform these functions:

• One is routed to a single fiber optic delay line that acts as a yardstick for comparison to the laser pulse time of flight.
• One is routed to an energy monitor for checking laser health.
• Two are routed to the altimetry detectors to carry the start pulses.
• A 3.3-micron diameter single-mode fiber optic is used as a collimator reference system because its tiny size simulates a point source.
• The sixth fiber is used for tracking purposes in the etalon filter in the GLAS Lidar system.
• The seventh barrel is for mounting an input test fiber.

This system survived thermal cycling from -40F (-40C) to 115F (46C) and vibration testing. The GLAS instrument with the Laser Pickoff system launched on January 12, 2003 from Vandenberg Air Force Base. The system has worked without problems since launch.

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