ASK OCE — May 10, 2006 — Vol. 1, Issue 8
On May 4, 1989, Magellan was carried aloft by the shuttle Atlantis from Kennedy Space Center, marking the first time that a planetary spacecraft was launched via the space shuttle.
This Atlantis took Magellan into low Earth orbit and then released it from the shuttle’s cargo bay. Magellan’s solid-fuel Inertial Upper Stage (IUS) then sent the spacecraft on a 15-month mission to Venus. After flying one and a half times around the sun, the spaceship arrived at Venus on August 10, 1990. At this point, another solid-fuel motor fired, putting the spacecraft into orbit around Venus.
Magellan’s polar orbit was very elliptical, taking it as close as 182 miles from Venus’s surface and as far away as 5,296 miles. The craft completed one orbit every 3 hours, 15 minutes.
When its orbit brought it closest to Venus, Magellan’s radar mapping equipment imaged a swath of the planet’s surface approximately 10 to 17 miles wide. After each orbit, the spacecraft radioed back a long ribbon-like strip of mapping data of the planet’s surface captured during the low-level pass. As the planet rotated under the spacecraft, Magellan collected strip after strip of radar image data, eventually covering the entire globe by the end of the planet’s 243-day annual orbital cycle.
Between September 1990 and May 1991, Magellan sent back detailed images of 84% of Venus’s surface. From May 1991 to September 1992, its radar mapped Venus on two more eight-month cycles. The end results were high-resolution maps of 98% of the planet’s surface, allowing scientists to construct three-dimensional views of the planet’s surface. Scientists were also able to compile a detailed gravity map of Venus.
In May 1993, NASA flight controllers lowered the spacecraft’s orbit using an untried technique called “aerobraking.” This novel maneuver slowed down Magellan and lowered its orbit by dipping Magellan into Venus’s atmosphere once every orbit, utilizing atmospheric drag.
In April 1994, Magellan began a sixth and final orbital cycle, collecting gravity data and conducting radar and radio science experiments. It captured high-resolution gravity data for an estimated 95% of the planet’s surface.
In early October 1994, with its mission completed, Magellan’s orbit was lowered to take readings of Venus’s outer atmosphere. Although much of the craft was vaporized, some sections are believed to have hit the planet’s surface intact.
Built partially from spare parts from other missions, the Magellan spacecraft was 15.4 feet long, with 12-foot high-gain antenna. The entire craft, including its retrorocket and a full propellant tank, weighed 7,612 pounds at launch.
