The Orbiting Geophysical Observatories

The Orbiting Geophysical Observatories are systems designed to fulfill a primary objective of conducting large numbers of significant, diversified experiments for making scientific and technological measurements within the earth´s atmosphere, the magnetosphere, and cislunar space to obtain a better understanding of earth-sun relationships and the earth as a planet. Configured to meet scientific requirements, the observatories include six appendages of different lengths for experiments requiring locations at a distance from the main body. Five degrees of freedom allow the capability of continuously orienting solar and antisolar, geocentric and antigeocentric, and orbital experiments within relatively close limits. Designed to include five basic subsystems of structure, stabilization and control, power, communications and data handling, and thermal control, the observatories have well-defined interfaces for experiments. Five of the six observatories in the program have already been launched and have returned significant scientific information. The last observatory is scheduled for launch in Spring 1969. Weights of the observatories range from 1073 to 1400 lb, including as many as 390 lb of experiments. One hundred six experiments have already been orbited on the five spacecraft, with 26 experiments scheduled for the last mission. Orbits have included three highly eccentric orbits inclined initially approximately 31° and two low-altitude nearly circular polar orbits. The orbit for the last mission, OGO-F, is of the latter type.