Explorer 49

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Explorer 49
RAE B.jpg
Artist's impression of Explorer 49 in orbit around the Moon
Mission type Radio astronomy
Operator NASA[1]
COSPAR ID 1973-039A
SATCAT № 6686
Mission duration 2 years
Spacecraft properties
Launch mass 328 kilograms (723 lb)
Start of mission
Launch date 10 June 1973, 14:13:00 (1973-06-10UTC14:13Z) UTC
Rocket Delta 1913[2]
Launch site Cape Canaveral LC-17B[2]
End of mission
Last contact August 1977 (1977-09)
Orbital parameters
Reference system Selenocentric
Periselene 1,123 kilometers (698 mi)
Aposelene 1,334 kilometers (829 mi)
Inclination 61.3 degrees
Epoch 15 June 1973
Lunar orbiter
Orbital insertion 15 June 1973, 07:21 UTC

Explorer 49 (also called RAE-B) was a 328 kilogram satellite launched on June 10, 1973 for longwave radio astronomy research. It had four 230-meter long X-shaped antenna elements, which made it one of the largest spacecraft ever built.[2]


Explorer 49 was launched after the termination of the Apollo program, and although it did not examine the Moon directly, it became the last American lunar mission until the launch of Clementine spacecraft in 1994.


This mission was the second of a pair of Radio Astronomy Explorer (RAE) satellites, Explorer 38 or RAE-A being the first. Explorer 49 was placed into lunar orbit to provide radio astronomical measurements of the planets, the Sun, and the galaxy over the frequency range of 25 kHz to 13.1 MHz. Since the spacecraft's design used gravity gradient booms, the lumpy lunar gravity field made for some interesting problems for the mission scientists.

See also[edit]


  1. ^ Nick Greene. "Explorer 49 Information". About.com. Retrieved 25 December 2010. 
  2. ^ a b c Gunter Dirk Krebs. "Explorer: RAE B". Retrieved 25 December 2010. 

External links[edit]