Goals: Magellan was designed to make quality radar maps of at least 70 percent of Venus' surface, providing a clear look at the topography below the planet's thick, perpetual cloak of clouds.
Accomplishments: Magellan mapped 98 percent of Venus' surface at a resolution of 100 to 150 meters (about the length of a football or soccer field), using synthetic aperture radar, a technique that simulates the use of a much larger radar antenna. It found that 85 percent of the surface is covered with volcanic flows and showed evidence of tectonic movement, turbulent surface winds, lava channels and pancake-shaped domes. Magellan also produced high-resolution gravity data for 95 percent of the planet and tested a new maneuvering technique called aerobraking, using atmospheric drag to adjust its orbit.
The spacecraft was commanded to plunge into Venus' atmosphere in 1994 as part of a final experiment to gather atmospheric data.
4 May 1989: Launch
10 Aug 1990: Venus Orbit Insertion
12 Oct 1994: Final Contact
Mission Type: Orbiter
Launch Vehicle: Space Shuttle Atlantis, STS-30R
Launch Site: Cape Canaveral, Fla., launch complex 39B
NASA Center: Jet Propulsion Laboratory
Spacecraft Mass: 3,445 kg
Spacecraft Instruments: 1) synthetic aperture radar; 2) gravimetry experiment; and 3) Magellan radio science occultation experiment
Spacecraft Power: Solar panels and rechargeable nickel-cadmium batteries
Maximum Power: 1029 W
Antenna Diameter: 3.7 m high-gain antenna
Total Cost: Aboout $680 million
Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, Monographs in Aerospace History No. 24, by Asif A. Siddiqi
National Space Science Data Center, http://nssdc.gsfc.nasa.gov/
Solar System Log by Andrew Wilson, published 1987 by Jane's Publishing Co. Ltd.
Magellan was the first deep space probe launched by the United States in almost eleven years, and it was also the first launched by the Space Shuttle. The spacecraft was designed to use a synthetic aperture radar (SAR) to map 70 percent of the Venusian surface down to a resolution of 120 to 300 meters.
Magellan was deployed by the STS-30R crew and released at 01:01 UT on 5 May 1989 from the payload bay of Atlantis. One hour later, a two-stage Inertial Upper Stage (IUS) fired to send the spacecraft on a trajectory to rendezvous with Venus. After three en route trajectory corrections (the first two on 21 May 1989 and 13 March 1990), Magellan arrived in Venus orbit on 10 August 1990. Orbital parameters were 297 x 8,463 kilometers at 85.5° inclination.
Six days after entering orbit, Magellan suffered a communications outage lasting 15 hours. After a second 17-hour interruption on 21 August, the ground sent up new preventative software to reset the system in case of such anomalies.
Beginning 15 September 1990, the spacecraft began returning high-quality radar images of the Venusian terrain that showed evidence of vulcanism, tectonic movement, turbulent surface winds, kilometers of lava channels, and pancake-shaped domes.
Magellan completed its first 243-day cycle (the time it took for Venus to rotate once under Magellan's orbit) of radar mapping on 15 May 1991, providing the first clear views of 83.7 percent of the surface. The spacecraft returned 1,200 gigabits of data, far exceeding the 900 gigabits of data from all NASA planetary missions combined at the time.
The spacecraft's second mapping cycle, already beyond the original goals of the mission, ended on 15 January 1992, raising coverage to 96 percent. A third cycle that focused on stereo imaging ended on 13 September 1992 and finished coverage at 98 percent. Further investigations focused on obtaining gravimetric data and performing aerobraking exercises (in 1993).
Contact was lost after 10:04 UT on 12 October 1994 as the spacecraft was commanded to plunge into the atmosphere to gather aerodynamic data. The spacecraft burned up in the Venusian atmosphere the following day at about 08:00 UT, after one of the most successful deep space missions.
Magellan found that at least 85 percent of the Venusian surface is covered with volcanic flows. Despite the high surface temperatures (475°C) and high atmospheric pressures (92 atmospheres), the complete lack of water makes erosion an extremely slow process. As a result, surface features can persist for hundreds of millions of years.