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Explorer 26



Explorer 26 was a spin-stabilized, solar-cell-powered spacecraft instrumented to measure trapped particles and the geomagnetic field. A 16-channel PFM/PM time-division multiplexed telemeter was used. The time required to sample the 16 channels (one frame period) was 0.29 s. Half of the channels were used to convey eight-level digital information. The other channels were used for analog information. During ground processing, the analog information was digitized with an accuracy of 1/800th of full scale. One analog channel was subcommutated in a 16-frame-long pattern and used to telemeter spacecraft temperatures, power system voltages, currents, etc. A digital solar aspect sensor measured the spin period and phase, digitized to 0.036 s, and the angle between the spin axis and sun direction to about 3-deg intervals. The spacecraft systems functioned well, except for some undervoltage turnoffs, until May 26, 1967, when the telemeter failed. The initial spin rate was 33 rpm, and the spin axis direction was right ascension 272.8 deg and declination 21.5 deg. The spin rate decreased with time to 2 rpm on September 9, 1965. For the balance of its life, the spacecraft was coning or tumbling at a rate of about 1 rpm.

Alternate Names

  • EPE-D
  • 00963

Facts in Brief

Launch Date: 1964-12-21
Launch Vehicle: Delta
Launch Site: Cape Canaveral, United States
Mass: 45.8 kg

Funding Agency

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


  • Space Physics

Additional Information

Questions or comments about this spacecraft can be directed to: Dr. John F. Cooper.



NameRoleOriginal AffiliationE-mail
Mr. Gerald W. LonganeckerProject ManagerNASA Goddard Space Flight Center 
Mr. Leo R. DavisProject ScientistNASA Goddard Space Flight Center 
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