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The purpose of the OGO 3 spacecraft, the third of a series of six Orbiting Geophysical Observatories, was to conduct many diversified geophysical experiments to obtain a better understanding of the earth as a planet. OGO 3 consisted of a main body that was parallelepipedal in form, two solar panels, each with a solar-oriented experiment package (SOEP), and two orbital plane experiment packages (OPEP). One face of the main body was designed to be earth pointing (Z axis), and the line connecting the two solar panels (X axis) was intended to be perpendicular to the earth-sun-spacecraft plane. The solar panels were able to rotate about the X axis. The OPEPs were mounted on, and could rotate about, an axis which was parallel to the Z axis and attached to the main body. Due to a failure in the attitude control subsystem on July 23, 1966, the spacecraft was put into a permanent spin mode about the Z axis. Both the orientation of the spin axis and the spin period were variable, the latter usually in the range 90 s to 125 s. At launch, the local time of apogee was 2300 h. OGO 3 carried 21 experiments. Thirteen of these were particle studies, and two were magnetic field studies. In addition, there was one each of the following types of experiments: interplanetary dust, VLF, Lyman-alpha, gegenschein, atmospheric composition, and radio astronomy. Real-time data were transmitted at 1, 8, or 64 kbs depending on the distance from the spacecraft to earth. Playback data were tape recorded at 1 kbs and transmitted at 64 kbs. Two wideband transmitters, one feeding into an omnidirectional antenna and the other feeding into a directional antenna, were used to transmit data. A special purpose telemetry system, feeding into either antenna, was also used to transmit wideband data in real time only. Tracking was accomplished by using radio beacons and a range and range-rate S-band transponder. Routine spacecraft operation was discontinued on December 1, 1969, after which only data from Heppner's experiment (E-11) was acquired. All spacecraft support terminated on February 29, 1972. By March 1971 spacecraft perigee had increased to 16,400 km and the inclination had increased to 75.8 deg.

Alternate Names

  • EOGO 3
  • S 49A
  • OGO-B
  • 02195
  • OGO3

Facts in Brief

Launch Date: 1966-06-07
Launch Vehicle: Atlas-Agena B
Launch Site: Cape Canaveral, United States
Mass: 514.8 kg

Funding Agency

  • NASA-Office of Space Science Applications (United States)


  • Planetary Science
  • Space Physics
  • Solar Physics
  • Astronomy

Additional Information

Questions and comments about this spacecraft can be directed to: Dr. H. Kent Hills



NameRoleOriginal AffiliationE-mail
Ms. Della StewartGeneral ContactNASA Goddard Space Flight Center
Mr. John J. QuannGeneral ContactNASA Goddard Space Flight Center
Dr. James P. HeppnerGeneral ContactNASA Goddard Space Flight Center
Mr. Wilfred E. ScullProject ManagerNASA Goddard Space Flight Center
Dr. George H. LudwigProject ScientistNASA Goddard Space Flight Center
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