A Thor-Agena launch vehicle, ready to launch the Discoverer 37 (KH-3) spacecraft, 13 January 1962
FunctionExpendable launch system
Country of originUnited States
HeightThor-Agena A: 28 m (92 ft)
Thor-Agena B: 31 m (102 ft)
Thor-Agena D: 31 m (102 ft)
Diameter2.44 m (8 ft 0 in)
MassThor-Agena A: 53,130 kg (117,130 lb)
Thor-Agena B: 56,507 kg (124,577 lb)
Thor-Agena D: 56,507 kg (124,577 lb)
Launch history
Launch sitesVandenberg Air Force Base
Total launches145
First flight21 January 1959
Last flight17 January 1968

Thor-Agena was a series of orbital launch vehicles.[1] The launch vehicles used the Douglas-built Thor first stage and the Lockheed-built Agena second stages. They are thus cousins of the more-famous Thor-Deltas, which founded the Delta rocket family. The first attempted launch of a Thor-Agena was in January 1959. The first successful launch was on 28 February 1959, launching Discoverer 1. It was the first two-stage launch vehicle to place a satellite into orbit.


Among other uses, the clandestine CORONA program used Thor-Agena from June 1959 until January 1968 to launch United States military reconnaissance satellites operated by the Central Intelligence Agency (CIA). During this program, Thor-Agena launch vehicles were used in 145 launch attempts,[2] now known to have been part of satellite surveillance programs.

Also, Alouette 1, Canada's first satellite, was launched on a Thor-Agena B.

1963 Mystery Cloud

On 28 February 1963, a Thor-Agena launch vehicle carrying a spy satellite into orbit was launched from Vandenberg Air Force Base. The launch vehicle went off course and mission control detonated the launch vehicle at an altitude of 44 km (27 mi) before it could reach orbit. The launch vehicle detonation produced a large circular cloud that appeared over the southwestern United States. Due to its mysterious nature, appearing at a very high altitude and being visible for hundreds of miles, the cloud attracted widespread attention and was published by the news media. The cloud was featured on the cover of Science Magazine in April 1963, Weatherwise Magazine in May 1963, and had a full page image published in the May issue of Life Magazine.[3][4] Prof. James MacDonald at the University of Arizona Institute for Atmospheric Physics investigated the phenomena and linked the it to the Thor launch vehicle launch after contacting military personnel at Vandenberg Air Force Base. When the launch records were later declassified, the United States Air Force released a memo explaining that the cloud was the result of a military operation.[5][6]


Thor-Agena A:[7]

Thor-Agena B:[9][10]

Thor-Agena D:[11][12]


  1. ^ Krebs, Gunter D. "Thor Agena". Gunter's Space Page.
  2. ^ Day, Dwayne; Logsdon, John; Latell, Brian (1998). Eye in the Sky: The Story of the Corona Spy Satellites. Smithsonian Institution Press. pp. 236–245. OCLC 36783934.
  3. ^ MacDonald, James (19 April 1963). "Stratospheric Cloud Over Northern Arizona". Science Magazine. Vol. 140, no. 3564. pp. 292–294. doi:10.1126/science.140.3564.292.b.
  4. ^ "Mystery Cloud". Life Magazine. 14 May 1963. p. 73.
  5. ^ Jackson, Jeff G. (26 January 1995), 30th Space Wing History, Vandenberg AFB, California: Department of the Air Force, pp. 1–2
  6. ^ MacDonald, James (15 June 1963). "Cloud Ring In The Upper Stratosphere" (PDF). Weatherwise. pp. 99–148.
  7. ^ Gunter D., Gunter D. "Thor-DM18 Agena-A". Gunter's Space Page.
  8. ^ "Display: Discoverer-14 1960-010A". NASA. 28 October 2021. Retrieved 5 November 2021. Public Domain This article incorporates text from this source, which is in the public domain.
  9. ^ Krebs, Gunter D. "Thor-DM21 Agena-B". Gunter's Space Page.
  10. ^ Krebs, Gunter D. "Thor-SLV2A Agena-B". Gunter's Space Page.
  11. ^ Krebs, Gunter D. "Thor-SLV2A Agena-D". Gunter's Space Page.
  12. ^ Krebs, Gunter D. "Thor-DM21 Agena-D". Gunter's Space Page.