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]

Discoverer 21

Mission type	Technology
Operator	US Air Force/ARPA
Harvard designation	1961 Zeta 1
COSPAR ID	1961-006A
SATCAT no.	00084
Spacecraft properties
Bus	Agena-B
Manufacturer	Lockheed
Launch mass	1,110 kilograms (2,450 lb)
Start of mission
Launch date	18 February 1961, 22:58 (1961-02-18UTC22:58Z) UTC
Rocket	Thor DM-21 Agena-B 261
Launch site	Vandenberg LC-1 launch pad 75-3-5
End of mission
Decay date	20 April 1962 (1962-04-21)
Orbital parameters
Reference system	Geocentric
Regime	Low Earth
Perigee altitude	243 kilometers (151 mi)
Apogee altitude	1,026 kilometers (638 mi)
Inclination	80.7 degrees
Period	97.4 minutes

The launch of Discoverer 21

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. McDowell, Jonathan. "Satellite Catalog". Jonathan's Space Page. Retrieved 30 June 2010.
4. 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.