Mission Overview

The fifth Orbiting Geophysical Observatory, OGO-5, was launched on 4 March 1968. The satellite, primarily devoted to Earth observation, was in a highly elliptical initial orbit with a 272 km perigee and an 148,228 km apogee. The orbital inclination was 31.1 degrees. The satellite took 3796 minutes to complete one orbit. Two experiments aboard OGO-5 produced cosmic high- energy results, although their intended target was the Sun. The spacecraft attitude control failed on 6 August 1971 and it was placed in a standby mode on 8 October 1971. Three experiments (none of which were related to cosmic high-energy detection) were reactivated from 1 June to 13 July 1972. Operation of OGO 5 terminated completely on 14 July 1972.

Launch Information
Launch Date: 1968-03-04 at 13:12:00 UTC
Launch Vehicle: Atlas-Agena D
Launch Site: Cape Canaveral, United States
Decay Date: 2011-07-02

Trajectory Details
Type: Orbiter
Central Body: Earth
Epoch start: 1968-03-04 13:12:00 UTC

Orbital Parameters
Periapsis 272.0 km
Apoapsis 148228.0 km
Period 3796.0 minutes
Inclination 31.100000381469727째
Eccentricity 0.9174659848213196


The Anderson et al. (University of California, Berkeley) Energetic Radiations from Solar Flares experiment was operational from March 1968 - June 1971. Primarily devoted to solar observations, it detected at least 11 cosmic X-ray bursts in time coincidence with gamma-ray bursts seen by other instruments. The detector was a 0.5 cm thick NaI(Tl) crystal with a 9.5 cm2 area. Data were accumulated into energy ranges of: 9.6-19.2, 19.2-32, 32-48, 48-64, 64-80, 80-104, 104-128, and › 128 keV. The data were sampled for 1. 15 seconds once every 2.3 seconds.

The gamma-ray instrument on-board, sensitive to energies from 25-100 MeV, was a six gap spark chamber with an effective area of ~ 100 cm2. It was called the Energetic Photons in Primary Cosmic Rays experiment (Hutchinson et al., Southampton University). It had an angular resolution of ~ 30 degrees (FWHM).


Spherical Electrostatic Probe
Plasma Temperature, Density and Flux
Low-Energy Integral Spectral Measurement
Energetic Radiations from Solar Flares
Study of Protons, Electrons, Positrons, and Gamma Rays
Electron and Proton Spectrometer
Low-Energy Proton and Electron Differential Energy Analyzer (LEPEDEA)
Energetic Photons in Primary Cosmic Rays
Cosmic Ray Electrons
Galactic and Solar Cosmic Ray Studies
Triaxial Electron Analyzer
Measurement of the Absolute Flux and Energy Spectrum of Electrons
Particle Wave Study
Triaxial Fluxgate Magnetometer
Magnetic Survey using Two Magnetometers
Triaxial Search-Coil Magnetometer
Plasma Spectrometer
Light Ion Mass Magnetic Spectrometer
50 kHz to 3.5 mHz Solar Radio Astronomy in Eight Steps
Ultraviolet Airglo
Geocoronal Lyman-Alpha Measurement
Solar X-Ray Emissions
Plasma Wave Detector
OPEP 2-Scan Mechanism
Electric Field Measurement
Low-Energy Heavy Cosmic Ray Particles


The satellite was Earth-pointing and passed regularly through the radiation belts, which led to severe restrictions on the sky regions which could be examined by the gamma-ray instrument. Other problems, such as an efficiency reduction in the anti-coincidence shield and data system difficulties, severely degraded the scientific return from the experiment. Data collection ceased altogether after 5 months. Gamma-ray emission from the galactic plane was monitored. No point sources were detected.