Identification of Satellites Possibly Active during the IMS and their Orbital Configurations

Abstract

A survey has been made to identify presently operating as well as planned spacecraft which may contribute measurements of the magnetosphere or interplanetary medium during the IMS. Fifty-one have been identified. Twenty-three are presently operating. The others are planned for launch prior to 1979. The total set consists of 25 scientific Earth-orbiting, 9 heliocentric and 17 communication, navigation or meteorological spacecraft, which carry environmental monitoring experiments. The orbital elements of each are displayed. In addition, techniques for the display of positions in various orbits are presented to illustrate how interesting configurations can be determined during the IMS. The positions of presently orbiting heliocentric spacecraft are shown at various intervals with respect to the nominal interplanetary magnetic field spiral and the Earth. Plots of the latest ISEE-A orbit in solar magnetospheric coordinates are presented to determine neutral-sheet crossing. The angular separation if IMP-H and -J approaches zero around the end of 1975. Periods where the separation is less than 10 R _E are given, other characteristics of the spacecraft orbits are discussed, and plans for the distribution of this information through the Satellite Situation Center are presented.