Magellan was an unmanned spacecraft designed to help scientists develop an understanding of the geological structure of Venus which was launched on May 4, 1989. It was named in honor of the Portuguese explorer who was the first person to circumnavigate the Earth. The usual 4 month journey to Venus was extended to 15 months in order to avoid a cosmic traffic jam. The craft's main objective was to provide detailed topographic maps of Venus' surface using a synthetic aperture radar to penetrate the planet's thick cloud cover. Magellan also conducted studies of Venus' surface altitude and its gravitational field.
The Magellan spacecraft was made almost completely out of spare parts left over from the other explorer satellites' construction. It had four radio antennas that were vital to its mission. The most important feature of this craft was the disk-shaped high-gain antenna located at the front of Magellan. This antenna was 12.1 feet (3.7 m) wide and served not only as a mapping radar, but as its main communications link with scientists from Earth. This antenna would map the surface of Venus and then point the antenna toward Earth and transmit that data. The medium-sized antenna measured the topography of the planet's mountains and valleys. The smaller low-gain antenna was used to communicate with Magellan while it was close to Earth. Three momentum wheels were used to steer Magellan instead of rocket power, this helped to conserve fuel.
Magellan was the first interplanetary probe to be launched into space aboard the space shuttle. Magellan was mounted in the cargo bay on springs and then released and sent on its way to Venus. It arrived and began to orbit Venus in August of 1990. Magellan slowly scanned the surface of the planet creating a detailed map of 98% of the surface, finishing this task on September of 1992. Scientists then used Magellan's orbital data to plot Venus' gravitational field. Magellan's mission came to an end on October 12, 1994 when scientists allowed it to burn up in the atmosphere of Venus. One of the most amazing statistics about this flight was that Magellan collected more data on its visit to Venus than all the previous explorer satellites combined.