Scientific Research SatellitesNumerous
Satellites are orbited to observe the space environment of the Earth or to study the
Sun, stars, and extragalactic objects over a wide range of wavelengths. Among those whose tour of active duty has been concluded are the Orbiting Geophysical Observatories (OGO); Orbiting Solar Observatories (OSO); Orbiting Astronomical Observatories (OAO); High Energy Astronomical Observatories (1977-79); the International
Ultraviolet Explorer (see ultraviolet astronomy); the X-ray astronomy
satellites Uhuru (1970-79) and Exosat (1983-86); and the IRAS infrared astronomy satellite. Current programs include further satellite entries for infrared, ultraviolet, and X-ray research, as well as the highly successful Hubble Space Telescope for optical astronomy.