Explorer 49 (RAE-B)
Explorer 49 (Radio Astronomy Explorer B) — a NASA radio telescope placed in orbit around the Moon on 15 June 1973, with antennas 229 m long. Each time it passed behind the Moon, the Moon blocked Earth's own radio noise, and its observations showed the far side to be the quietest radio location in the Earth–Moon system. Contact was lost in August 1977. (Its orbit is drawn to its published height; its plane and position on it are representative.)
Key facts
Mission & specifications
Mission
- Operator
- NASA
- Launched
- June 10, 1973
- Status
- Completed
Mission
Explorer 49, the second Radio Astronomy Explorer (RAE-B), was a NASA radio telescope for the long radio waves that Earth's atmosphere blocks — 25 kHz to 13.1 MHz — coming from the Sun, the planets and the galaxy. It was launched on 10 June 1973 and put into lunar orbit on 15 June by a 20-second burn of its kick motor, about 1,100 km above the surface. Its antennas were enormous for so small a craft: two V-shaped antennas 229 m long, one pointing toward the Moon and one away, a 37 m dipole and a 192 m damper boom that kept it steady. The Moon was part of the instrument. Earth is a surprisingly loud radio source, and every time the spacecraft passed behind the Moon, Earth's radio noise dropped by factors of 10 to 1,000. That showed the lunar far side to be the quietest radio location in the Earth–Moon system. It observed the galaxy, solar and Jovian radio bursts and Earth's own auroral radio emission until contact was lost in August 1977.
- 1973Explorer 49 launches toward the Moon on a Delta rocketLaunch
A radio telescope for waves that Earth's atmosphere blocks.
- 1973Into lunar orbitArrival
A 20-second burn of its kick motor, about 1,100 km above the surface.
- 1973Observations beginMilestone
At first with only its 37 m dipole antenna out; the 229 m antennas follow.
Images
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