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Laser Tracking Reflector

NSSDCA ID: 1965-089A-02

Mission Name: GEOS 1
Principal Investigator:Dr. Henry H. Plotkin


Laser corner reflectors, composed of fused quartz cubes with silvered reflecting surfaces, were used for determining the spacecraft's range and angle. The 322 cubes were mounted on fiberglass panels on the bottom rim of the spacecraft and provided a total reflecting area of 0.18 sq m. The reflectors conserved the narrow beamwidth of incoming light and reflected a maximum signal to the ground, almost exactly to where it originated. Fifty percent of the light which 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 for the beam to return to the earth was recorded by a digital counter. The reflected laser pulse was also photographed against the stellar background. Total time traveled by the light pulses was also considered in the optical laser tracking system.

Alternate Names

  • GEOS1/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
Dr. Henry H. PlotkinPrincipal InvestigatorNASA Goddard Space Flight Center
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