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 Defense; the USAF Space and Missile Systems organization 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.

The spacecraft used 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. Advanced Velas were 26-sided polygons 1.42 m in diameter and 1.17 m high, weighed 231 kg in orbit. Total payload mass was 63 kg. Two optical bhangmeters observed the Earth. Twelve external X-ray detectors and 18 internal neutron and gamma-ray detectors detected high-altitude or space nuclear explosions.

Design Life: 18 months. Typical orbit: Average 102,000 km, 38 deg inclination. Maximum Diameter: 1.50 m (4.90 ft). Mass: 317 kg (698 lb). Associated Launch Vehicle: Titan 3C.

• 1965 March 1 - TRW awarded contract for the Advanced Vela spacecraft -

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

• 1967 April 28 - Vela 8 - Launch Site: Cape Canaveral. Launch Vehicle: Titan. Mass: 317 kg (698 lb). Perigee: 107,372 km (66,717 mi). Apogee: 114,578 km (71,195 mi). Inclination: 33.10 deg. Period: 6,668.10 min.

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

• 1967 April 28 - Vela 7 - Launch Site: Cape Canaveral. Launch Vehicle: Titan. Mass: 317 kg (698 lb). Perigee: 108,948 km (67,697 mi). Apogee: 112,627 km (69,983 mi). Inclination: 32.10 deg. Period: 6,652.10 min.

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

• 1969 May 23 - Vela 9 - Launch Site: Cape Canaveral. Launch Vehicle: Titan. Mass: 317 kg (698 lb). Perigee: 77,082 km (47,896 mi). Apogee: 145,638 km (90,495 mi). Inclination: 61.60 deg. Period: 6,700.90 min.

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

• 1969 May 23 - Vela 10 - Launch Site: Cape Canaveral. Launch Vehicle: Titan. Mass: 317 kg (698 lb). Perigee: 72,080 km (44,780 mi). Apogee: 150,633 km (93,598 mi). Inclination: 61.00 deg. Period: 6,700.70 min.

  Radiation, low-energy particle, solar flare data. Space craft engaged in investigation of spaceflight techniques and technology (US Cat A).

• 1970 April 8 - Vela 12 - Launch Site: Cape Canaveral. Launch Vehicle: Titan. Mass: 317 kg (698 lb). Perigee: 101,261 km (62,920 mi). Apogee: 121,227 km (75,326 mi). Inclination: 61.20 deg. Period: 6,691.00 min.

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

• 1970 April 8 - Vela 11 - Launch Site: Cape Canaveral. Launch Vehicle: Titan. Mass: 317 kg (698 lb). Perigee: 103,570 km (64,350 mi). Apogee: 119,313 km (74,137 mi). Inclination: 57.40 deg. Period: 6,707.90 min.

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