Did you know...
...that the Magellan mission generated more digital data than all previous U.S. planetary missions combined?
...that during mapping, Magellan's radar sensor comsumes 200 watts of electricity? This is roughly the equivalent of a bright floor lamp.
...that this project was named after Ferdinand Magellan, the man who almost circumnavigated the world?
...that 99% of Magellan's trip through space was unpowered?
Magellan was the first planetary spacecraft to be launched by a space shuttle when it was carried aloft by the shuttle Atlantis from Kennedy Space Center in Florida on May 4, 1989. Atlantis took Magellan into low Earth orbit, where it was released from the shuttle's cargo bay. A solid-fuel motor called the Inertial Upper Stage (IUS) then fired, sending Magellan on a 15-month cruise looping around the sun 1-1/2 times before it arrived at Venus on August 10, 1990. A solid-fuel motor on Magellan then fired, placing the spacecraft in orbit around Venus.
Magellan's initial orbit was highly elliptical, taking it as close as 294 kilometers (182 miles) from Venus and as far away as 8,543 kilometers (5,296 miles). The orbit was a polar one, meaning that the spacecraft moved from south to north or vice versa during each looping pass, flying over Venus's north and south poles. Magellan completed one orbit every 3 hours, 15 minutes.
During the part of its orbit closest to Venus, Magellan's radar mapper imaged a swath of the planet's surface approximately 17 to 28 kilometers (10 to 17 miles) wide. At the end of each orbit, the spacecraft radioed back to Earth a map of a long ribbon-like strip of the planet's surface captured on that orbit. Venus itself rotates once every 243 Earth days. As the planet rotated under the spacecraft, Magellan collected strip after strip of radar image data, eventually covering the entire globe at the end of the 243-day orbital cycle.
By the end of its first such eight-month orbital cycle between September 1990 and May 1991, Magellan had sent to Earth detailed images of 84 percent of Venus's surface. The spacecraft then conducted radar mapping on two more eight- months cycles from May 1991 to September 1992. This allowed it to capture detailed maps of 98 percent of the planet's surface. The follow-on cycles also allowed scientists to look for any changes in the surface from one year to the next. In addition, because the "look angle" of the radar was slightly different from one cycle to the next, scientists could construct three-dimensional views of Venus's surface.
During Magellan's fourth eight-month orbital cycle at Venus from September 1992 to May 1993, the spacecraft collected data on the planet's gravity field. During this cycle, Magellan did not use its radar mapper but instead transmitted a constant radio signal to Earth. If it passed over an area of Venus with higher than normal gravity, the spacecraft would slightly speed up in its orbit. This would cause the frequency of Magellan's radio signal to change very slightly due to the Doppler effect--much like the pitch of a siren changes as an ambulance passes. Thanks to the ability of radio receivers in the NASA/JPL Deep Space Network to measure frequencies extremely accurately, scientists could build up a detailed gravity map of Venus.
At the end of Magellan's fourth orbital cycle in May 1993, flight controllers lowered the spacecraft's orbit using a then-untried technique called aerobraking. This maneuver sent Magellan dipping into Venus's atmosphere once every orbit; the atmospheric drag on the spacecraft slowed down Magellan and lowered its orbit. After the aerobraking was completed between May 25 and August 3, 1993, Magellan's orbit then took it as close as 180 kilometers (112 miles) from Venus and as far away as 541 kilometers (336 miles). Magellan also circled Venus more quickly, completing an orbit once every 94 minutes. This new, more circularized orbit allowed Magellan to collect better gravity data in the higher northern and southern latitudes near Venus's poles.
After the end of that fifth orbital cycle in April 1994, Magellan began a sixth and final orbital cycle, collecting more gravity data and conducting radar and radio science experiments. By the end of the mission, Magellan captured high-resolution gravity data for an estimated 95 percent of the planet's surface.
In September 1994, Magellan's orbit was lowered once more in another test called a "windmill experiment." In this test, the spacecraft's solar panels were turned to a configuration resembling the blades of a windmill, and Magellan's orbit was lowered into the thin outer reaches of Venus's dense atmosphere. Flight controllers then measured the amount of torque control required to maintain Magellan's orientation and keep it from spinning. This experiment gave scientists data on the behavior of molecules in Venus's upper atmosphere, and lent engineers new information useful in designing spacecraft.
On October 11, 1994, Magellan's orbit was lowered a final time. Within two days after that maneuver, the spacecraft became caught in the atmosphere and plunged to the surface. Although much of Magellan would was vaporized, some sections hit the planet's surface intact.
Magellan - mission overview, some images
Magellan Image Server - tons of images, extremely thorough
Magellan Mission to Venus - detailed mission info, news, images
* Picture credit - JPL
* This text was adapted from the JPL Magellan Project Home Page.