Explorer 49

Explorer 49

Artist's impression of Explorer 49 in orbit around the Moon
Mission type	Radio astronomy
Operator	NASA
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
Launch site	Cape Canaveral LC-17B
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.

Launch

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.

Orbit

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

• 1973 in spaceflight
• Timeline of artificial satellites and space probes

External links

• Astronautix.com Page on the Radio Astronomy Explorers
• National Space Science Data Center Page on RAE-B (Explorer 49)
• Delta-95, RAE-B Operations Summary
• On Obtaining Lunar Mission Launch Opportunities (Report on Launch/Trajectory planning for the RAE-B mission)
• RAE-B antenna aspect system (Report on the camera system used to verify the antenna deployment of Explorer 49)
• RAE-B antenna aspect processor (Report on the processing hardware for the RAE-B Camera system)
• Proposed gravity-gradient dynamics experiments in lunar orbit using the RAE-B spacecraft

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