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ERS 27



The primary objectives of the spacecraft were (1) to monitor soft x rays (2 to 14 A) and high-energy x rays (33 to 90 KeV) emanating from the sun, and (2) to measure solar protons resulting from solar flares. The secondary mission objectives was to measure energetic particles in near-earth space over the energy ranges 1 to 80 MeV for protons and 0.04 to 3.3 MeV for electrons. The spacecraft was a spin-stabilized regular octahedron that weighed 6.3 kg and measured 29.2 cm along each triangular edge. Each of the eight triangular faces contained 102 solar cells, and the total average power output was about 4 w. The spin rate was about 12 rpm. The experiment complement consisted of six GM tubes, two plastic scintillation counters, one sodium iodide scintillation counter, one lithium drifted silicon detector, and one surface barrier detector to measure charged particles, x rays, gamma rays, and cosmic rays in the near-earth environment. All detector counting rates were converted to analog signals by logarithmic count rate meters and were transmitted over irig channel 5 with a PAM/FM/PM system that radiated 1 w of RF power. Twenty-three different measurements, including housekeeping data, were time commutated by a 16-channel commutator which had one segment subcommutated eight times. Each measurement was sampled for 4.4 sec, and the response of the overall system was limited by a 0.1-sec low pass filter in the subcarrier oscillator. The spacecraft also contained a solar aspect sensor system to determine the angle between the satellite-sun line and the satellite spin axis to within 7.5 deg. The spacecraft operated successfully from launch until June 1968, when a preset timer turned off the transmitter. However, no data were collected after November 1, 1967.

Alternate Names

  • 02769
  • ERS27
  • ORS 3(F)
  • OV5-1

Facts in Brief

Launch Date: 1967-04-28
Launch Vehicle: Titan III-C
Launch Site: Cape Canaveral, United States
Mass: 6.3 kg

Funding Agency

  • Department of Defense-Department of the Air Force (United States)


  • Space Physics
  • Solar Physics
  • Astronomy

Additional Information

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



NameRoleOriginal AffiliationE-mail
Mr. H. T. SliffProject ManagerNASA Goddard Space Flight Center
Dr. Louis S. WalterProject ScientistNASA Goddard Space Flight Center
Dr. James B. GardnerProject ScientistTRW Systems Group
Maj R. A. BenaProgram ManagerPhillips Laboratory (nee USAF Geophysics Lab, nee Cambridge Labs)
Mr. R. J. MartinProject EngineerTRW Systems Group
Dr. G. Kenneth YatesProgram ScientistPhillips Laboratory (nee USAF Geophysics Lab, nee Cambridge Labs)
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