Like its predecessor, the Vela, the Advanced Vela series of
spacecraft were designed to monitor worldwide compliance with the 1963 nuclear test ban
treaty. The Advanced series added atmospheric nuclear detonation detection to its
capabilities. Additionally, it monitored solar activity (providing radiation warnings for
crewed missions), terrestrial lightning activity and celestial X/gamma-ray radiation. 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.
The spacecraft featured the 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.
Total payload mass was 63 kg. Two optical bhangmeters observing Earth. Twelve external
X-ray detectors and 18 internal neutron and gamma-ray detectors.
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