OGO 5

Description

The objectives of the OGO 5 spacecraft, the fifth of a series of six Orbiting Geophysical Observatories, were to conduct many diversified geophysical experiments for a better understanding of the earth as a planet and to develop and operate a standardized observatory-type spacecraft. OGO 5 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 earth pointing (Z-axis), and the line connecting the two solar panels (X-axis) was 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 that was parallel to the Z-axis that was attached to the main body. At launch, the initial local time of apogee was 0944 h. OGO 5 carried 25 experiments, 17 of which were particle studies, and two were magnetic field studies. In addition, there was one each of the following types of experiments: radio astronomy, UV spectrum, Lyman-alpha, solar X ray, plasma waves, and electric field. Real-time data were transmitted at 1, 8, and 64 kbs depending on the distance from the spacecraft to the earth. Playback data were tape recorded at 1 kbs and transmitted at 64 kbs. Two wide-band 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 wide-band data in real time only. Tracking was accomplished by using radio beacons and a range and range-rate, S-band transponder. The spacecraft attitude control failed on August 6, 1971, after 41 months of normal operation. The spacecraft was placed in a standby status on October 8, 1971. Four experiments (Meyer, Blamont, Thomas, and Simpson) were reactivated for the period from June 1 to July 13, 1972, after which all operational support terminated. Spacecraft orbit parameters changed significantly over the spacecraft life. By April 1971, spacecraft perigee had increased to 26,400 km and inclination had increased to 54 deg.