Vela 1B was one of two spin stabilized (2.1 rev/sec) 134-kg satellites comprising the first launch in a series of six Vela launches. The orbits of the two satellites on each launch were basically circular at about 17 earth radii and were spaced 180 deg apart. Their objectives were to monitor nuclear weapons explosions in space and to study x-rays, gamma-rays, neutrons, and charged particles as the satellites passed through interplanetary space, the bow shock, the magnetosheath, and the magnetotail. The satellite operated in either a real-time mode (one data frame/sec) or a memory store mode (one data frame every 256 sec). The spacecraft was operated in the real-time mode about 40 percent of the time and in the store mode for the rest of the time until the next Vela launch. At this time, tracking priority was given to the new spacecraft, and the older spacecraft was operated in the store mode only. There had been less and less data coverage of these satellites with each succeeding launch.