Like its predecessor, the Vela (meaning "watchman" in Spanish) , the Advanced Vela series of spacecraft were designed to monitor world-wide compliance with the 1963 nuclear test ban treaty. The Vela Nuclear Detection Satellites were launched in pairs into high altitude orbits to detect possible nuclear explosions in space and on earth. The original Vela satellites were so successful, each operating for at least 5 years, that a planned acquisition of a fourth and fifth set of pairs was cancelled. Instead, TRW was awarded a further contract in March 1965 for an Advanced Vela spacecraft series. The Advanced series added atmospheric nuclear detonation detection to its capabilities. Additionally, it monitored solar activity (providing radiation warnings for manned missions), terrestrial lightning activity and celestial X/gamma-ray radiation. The project was directed by the Advanced Research Projects Agency of the Department of Defence; the USAF Space and Missile Systems organisation was responsible for the development of the-spacecraft. Prime Contractor was TRW Systems Group of TRW Inc. The first of a pair of Advanced Velas was launched in April 1967. All six spacecraft operated for more than 10 years. Their nuclear detection role was assumed by IMEWS in the 1970s. Touted as the longest continuously operating space system in 1985 when USAF shut down the last 3 spacecraft. Spacecraft: First dual-spin, zero momentum attitude control system. In launch configuration, two 26-sided polyhedron spacecraft were connected by a central cylinder containing an apogee motor. Body mounted solar cells generated 120 watts. Advanced Velas were 26-sided polygons 1.42 m in diameter and 1.17 m high, weighed 231 kg in orbit. Payload: Total payload mass was 63 kg. Two optical bhangmeters observing Earth. Twelve external X-ray detectors and 18 internal neutron and gamma-ray detectors.

Design Life: 18 months. Maximum Diameter: 1.5 m. Total Mass: 317 kg.

The Advanced series added atmospheric nuclear detonation detection to its capabilities. Additionally, it monitored solar activity, terrestrial lightning, and celestial X/gamma-ray radiation.

Space craft engaged in investigation of spaceflight techniques and technology (US Cat A).

Solar flare particle detectors. Space craft engaged in investigation of spaceflight techniques and technology (US Cat A).

Space craft engaged in investigation of spaceflight techniques and technology (US Cat A).

• 2 - McDowell, Jonathan, The United Nations Registry of Space Objects, Harvard University, 1997. HTML when accessed: http://hea-www.harvard.edu/QEDT/jcm/space/un/un.html
• 6 - JPL Mission and Spacecraft Library, Jet Propulsion Laboratory, 1997. HTML when accessed: http://msl.jpl.nasa.gov/home.html
• 405 - Aerospace Yearbook, 1966, .