A series of 6 Orbiting Geophysical Observatories (OGOs) were put into orbit by NASA between 1964 and 1969. They were intended to study the Earth's atmosphere, magnetosphere, and the space between the Earth and Moon.

OGO 1 was successfully launched from Cape Kennedy on 5 September 1964 and placed into an initial orbit of 281 x 149,385 km at 31 degrees inclination. Two experiment booms failed to properly deploy, with one of the booms obscuring a horizon scanner's view of earth. As a result, the spacecraft attitude could not be earth oriented and OGO 1 remained spin stabilized at 5 rpm. Nevertheless, data from all 20 experiments on board was received, although at a “less than expected capacity” from some of them. During September 1964, acceptable data were received over 70% of the orbital path. Spacecraft operation was restricted to Spring and Fall due to power supply limitations. There were 11 such 3-month periods prior to the spacecraft being put into stand-by mode on 25 November 1969. OGO 1 was completely terminated on 1 November 1971.


On board was the Positron Search and Gamma-Ray Spectrum experiment of Cline et al. It was designed to determine whether low-energy (0-3 MeV) positrons are trapped temporarily or permanently in the Van Allen regions and whether low-energy solar and interplanetary positrons exist at the edge of the Earth's magnetic field. A secondary objective was to detect gamma-ray bursts from the Sun in the energy range 80 keV - 1 MeV. The experiment consisted of 3 CsI crystals surrounded by a plastic anti-coincidence shield. The output of the whole unit was monitored by 3 PMTs. Once every 18.5 seconds, integral intensity measurements were made in each of 16 energy channels which were equally spaced over the .08-1 MeV range.


Triaxial Search-Coil Magnetometer
Magnetic Survey using Two Magnetometers
Spherical Ion and Electron Trap
Planar Ion and Electron Trap
Radio Propagation
Positive Ion Composition
Interplanetary Dust Particles
Wideband and Narrow-Band Step Frequency VLF Receivers
Radio Astronomy
Geocoronal Lyman-Alpha Scattering
Gegenschein Photometry
Solar Cosmic Rays
Electrostatic Plasma Analysis (Protons .1-18 keV)
Plasma Probe, Faraday Cup
tPositron Search and Gamma Ray Spectrum
Trapped Radiation Scintillation Counter
Cosmic-Ray Isotopic Abundance
Cosmic-Ray Spectra and Fluxes
Trapped Radiation and High-Energy Protons
Ionization Chamber
Electron Spectrometer

Launch-Orbit Information

Trajectory Details

Type: Orbiter
Central Body: Earth
Epoch start: 1964-09-05 01:23:00 UTC

Orbital Parameters

Periapsis Apoapsis Period Inclination Eccentricity
281 km 149,385 km 3,839 minutes 31.2° 0.91795


The experiment did not achieve its goals due to electrical interference and secular degradation of the PMT responses. However, searching back through the data after the discovery of cosmic gamma-ray bursts by the Vela satellites revealed the detection of one or more such events in the OGO 1 data.