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Radar Altimeter

NSSDCA ID: 1962-012A-03

Mission Name: Ranger 4
Principal Investigator:Mr. Walter E. Brown, Jr.


A radar altimeter was included in the experiment package to initiate capsule separation and retrorocket ignition 19 to 25 km above the lunar surface and to measure the radar reflectivity of the lunar surface and study its properties. The instrument was a standard pulse-type radar with peak power output from the magnetron transmitter of between 150 and 400 w. The instrument had a frequency of 9400 mHz and a pulse repetition rate of 500 to 600 pps. The superheterodyne receiver bandwidth was 12 to 16 mHz, and its noise figure was 11 to 12 db. Antenna beamwidth was 4.5 deg. The altimeter was designed to begin measurements on command from earth at 198 to 55 km from the moon (nominally 137 km). The planned lifetime of measurement was 9 sec to 2 min. Because of a spacecraft communcations failure early in the flight, the experiment returned no data.

Alternate Names

  • Ranger4/RadarAltimeter


    Additional Information

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



    NameRoleOriginal AffiliationE-mail
    Mr. Walter E. Brown, Jr.Principal InvestigatorNASA Jet Propulsion Laboratory
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