The Vela 5B spacecraft: long-term X-ray astronomy.

The Vela spacecraft 5A and 5B, which contained a considerable array of detectors, for gamma-rays, X-rays, charged particles, and visible light are described. Launched in 1969, these spacecraft comprised the fifth in a series of launches undertaken by the USAF in 1963 to monitor possible violations of the Limited Test Ban treaty. Vela 5B, in particular, produced a complete and lengthy survey of the X-ray sky, covering the ten years to June 1979.