Discoverer 21
Mission typeTechnology
OperatorUS Air Force/ARPA
Harvard designation1961 Zeta 1
COSPAR ID1961-006A
SATCAT no.00084Edit this on Wikidata
Spacecraft properties
BusAgena-B
ManufacturerLockheed
Launch mass1,110 kilograms (2,450 lb)
Start of mission
Launch date18 February 1961, 22:58 (1961-02-18UTC22:58Z) UTC
RocketThor DM-21 Agena-B 261
Launch siteVandenberg LC-1 launch pad 75-3-5
End of mission
Decay date20 April 1962 (1962-04-21)
Orbital parameters
Reference systemGeocentric
RegimeLow Earth
Perigee altitude243 kilometers (151 mi)
Apogee altitude1,026 kilometers (638 mi)
Inclination80.7 degrees
Period97.4 minutes
 
The launch of Discoverer 21

Discoverer 21, also known as RM-2, was an American satellite which was launched in 1961. It was a technology demonstration spacecraft, based on an Agena-B.[1]

The launch of Discoverer 21 occurred at 22:58 UTC on 18 February 1961. A Thor DM-21 Agena-B rocket was used, flying from launch pad 75-3-5 at the Vandenberg Air Force Base.[2] Upon successfully reaching orbit, it was assigned the Harvard designation 1961 Zeta 1.

Discoverer 21 was operated in a low Earth orbit, with a perigee of 243 kilometres (151 mi), an apogee of 1,026 kilometres (638 mi), 80.7 degrees of inclination, and a period of 97.4 minutes.[3] The satellite had a mass of 1,110 kilograms (2,450 lb),[4] and was used to demonstrate an engine restart,[5] and to test infrared sensors for the Midas programme.[4] It remained in orbit until 20 April 1962,[3] when it decayed and reentered the atmosphere.

References

  1. ↑ Krebs, Gunter. "RM 1, 2 (Discoverer 19, 21)". Gunter's Space Page. Retrieved 30 June 2010.
  2. ↑ McDowell, Jonathan. "Launch Log". Jonathan's Space Page. Retrieved 30 June 2010.
  3. 1 2 McDowell, Jonathan. "Satellite Catalog". Jonathan's Space Page. Retrieved 30 June 2010.
  4. 1 2 Wade, Mark. "Midas". Encyclopedia Astronautica. Archived from the original on 20 November 2010. Retrieved 30 June 2010.
  5. ↑ "Discoverer 21". NSSDC Master Catalog. NASA. Retrieved 30 June 2010.


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