|Mission type||Radio astronomy|
|Mission duration||4 years and 2 months (launch date to last contact)|
|Launch mass||328 kilograms (723 lb)|
|Start of mission|
|Launch date||June 10, 1973, 14:13:00UTC|
|Launch site||Cape Canaveral LC-17B|
|End of mission|
|Last contact||August 1977|
|Periselene altitude||1,123 kilometers (698 mi)|
|Aposelene altitude||1,334 kilometers (829 mi)|
|Epoch||June 15, 1973|
|Orbital insertion||June 15, 1973, 07:21 UTC|
Explorer 49 (also called Radio Astronomy Explorer-B (RAE-B)) was a 328-kilogram (723 lb) satellite launched on June 10, 1973, for long wave radio astronomy research. It had four 230-metre-long (750 ft) X-shaped antenna elements, which made it one of the largest spacecraft ever built.
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 orbital mission until the launch of Clementine spacecraft in 1994. It was launched on June 10, 1973, 14:13:00 UTC in the Rocket Delta 1913 from the Launch site Cape Canaveral LC-17B.
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 was a problem for the mission scientists.
Explorer 49 was placed in lunar orbit to record radio measurements from 25 kHz to 13.1 MHz of the Milky Way galaxy. Explorer 49 was placed in to lunar orbit so that radio waves from Earth would not be as big of an interference as Explorer 38 had discovered.
The principal investigator for all the experiments was Dr. Robert G. Stone.
Data were returned to Earth via either a low-power UHF/(400 MHz) transmitter, in real time, or stored in an onboard tape recorder and transmitted to Earth via a high-power UHF transmitter (400 MHz). Two tape recorders provided backup storage.
The third burst receiver on the dipole antenna failed after the first week, and no data resulted from the receiver.
A mechanical flaw in the lower V-antenna caused the leg to only deploy to a length of 183 metres (600 ft) instead of 229 metres (751 ft). This was corrected in November 1974, and the leg extended to the full intended length.