Explorer 21

Explorer 21
Explorer 21 satellite
NamesIMP-B
IMP-2
Interplanetary Monitoring Platform-2
Mission typeSpace physics
OperatorNASA
COSPAR ID1964-060A Edit this at Wikidata
SATCAT no.00889
Spacecraft properties
BusIMP
ManufacturerGoddard Space Flight Center
Launch mass138 kg (304 lb)
Power4 deployable solar arrays and batteries
Start of mission
Launch date4 October 1964, 03:45:00 GMT[1][2]
RocketThor-Delta C
(Thor 392 / Delta 026)
Launch siteCape Canaveral, LC-17A[3]
ContractorDouglas Aircraft Company
Entered service4 October 1964
End of mission
Last contact13 October 1965
Decay date1 January 1966[4]
Orbital parameters
Reference systemGeocentric orbit[4]
RegimeHighly elliptical orbit
Perigee altitude917 km (570 mi)
Apogee altitude94,288 km (58,588 mi)
Inclination33.70°
Period2080.00 minutes
Instruments
← IMP-A
IMP-C →

Explorer 21, also called IMP-B, IMP-2 and Interplanetary Monitoring Platform-2, was a NASA satellite launched as part of Explorer program. Explorer 21 was launched on 4 October 1964, at 03:45:00 GMT from Cape Canaveral (CCAFS),[5] Florida, with a Thor-Delta C launch vehicle. Explorer 21 was the second satellite of the Interplanetary Monitoring Platform, and used the same general design as its predecessor, Explorer 18 (IMP-A), launched the previous year, in November 1963. The following Explorer 28 (IMP-C), launched in May 1965, also used a similar design.[6]

  1. ^ "Jonathan's Space Report". 21 July 2021. Retrieved 7 November 2021.
  2. ^ "Letter dated 22 December 1964 from the Permanent Representative of the United States of America addressed to the Secretary-General" (PDF). COMMITTEE ON THE PEACEFUL USES OF OUTER SPACE (64-28156). Retrieved 5 December 2022.
  3. ^ "NASA'S YEAR". Flight International. Retrieved 9 June 2018.
  4. ^ a b Cite error: The named reference Trajectory was invoked but never defined (see the help page).
  5. ^ "Explorer-21 Satellite Falls Far Short Of Orbital Goal". The Palm Beach Post. Vol. 56, no. 202. UPI. 5 October 1964. p. 8. Archived from the original on 25 January 2024. Retrieved 9 June 2018 – via Newspapers.com.
  6. ^ "Explorer-series reference images". Retrieved 4 July 2021.