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Laser Tracking Reflector

NSSDCA ID: 1968-002A-02

Mission Name: GEOS 2
Principal Investigator:Dr. Henry H. Plotkin


Laser corner reflectors, composed of 322 fused quartz cubes with silvered reflecting surfaces, were used for determining the spacecraft range and angle. The cubes, which were mounted on fiberglass panels on the bottom rim of the spacecraft, provided a total reflecting area of 0.18 sq m. The reflectors conserved the narrow beamwidth of incoming light and provided a maximum signal to the ground almost exactly to where it originated. Fifty percent of the light that struck the prism area at a 90-deg angle was reflected within a beam of 20 arc-s. Reflected light received by ground telescopes was amplified by a photomultiplier tube that converted the optical impulse to an electrical signal. The time required for the beam to return to earth was recorded by a digital counter. The reflected laser pulse was also photographed against the stellar background, and the total time traveled by the light pulses was considered in the optical laser tracking system. Laser tracking was the responsibility of AFCRL, SAO, GSFC Optical Research, and international laser stations.

Alternate Names

  • GEOS2/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. StephanidesOther InvestigatorNASA Goddard Space Flight Center
Dr. Henry H. PlotkinPrincipal InvestigatorNASA Goddard Space Flight Center
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