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Laser Tracking Reflector

NSSDCA ID: 1975-027A-04

Mission Name: GEOS 3
Principal Investigator:Mr. Chris C. Stephanides


Laser corner reflectors, composed of 264 35-mm cubes, and ground-based laser systems were used to obtain precise satellite tracking information. The Applied Physics Laboratory provided the laser cube reflector panels. The cubes were configured on the lateral surface of a conic frustum, with the lateral surface of the frustum adjoining the bottom, earth-oriented surface of the spacecraft at a 45-deg angle. The base of the frustum measured approximately 0.9 meter in diameter. When illuminated by a laser light pulse from the ground, each retroreflector cube in the array reflected the light ray back to a special telescope receiver on the ground. The reflected light was picked up by the telescope, and the optical impulses converted to an electrical signal. A digital counter recorded the time when the light beam was returned to the ground. The total travel time of the light pulses, from ground to satellite and back to the ground, measured the distance to the satellite, thus forming the basis of the satellite optical laser system. The following observational systems acquired the necessary data: NASA/Wallops Laser Ranging Systems, SAO (Smithsonian Astrophysical Observatory) Laser Ranging Systems, GSFC Laser Ranging Systems, and other national and international laser stations as determined.

Alternate Names

  • GEOS3/LaserTrackingReflector


  • Earth Science: Geophysics/Geodesy

Additional Information

Questions and comments about this experiment can be directed to: Coordinated Request and User Support Office



NameRoleOriginal AffiliationE-mail
Mr. Chris C. StephanidesPrincipal InvestigatorNASA Goddard Space Flight Center
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