Deep Impact – A Review of the World's Pioneering Hypervelocity Impact Mission☆

Abstract On July 4th, 2005, in celebration of our nation's birthday, NASA's Deep Impact Impactor spacecraft collided with comet Tempel1 at 10 km/sec – marking the first hypervelocity impact of a celestial body by a human-made spacecraft. With closing speeds of 23,000 mph, the Impactor's active guidance system steered it to impact on a sunlit portion of the comet's surface. As it closed in on Tempel 1, the Impactor's camera relayed close-up images of the comet's surface to the Flyby spacecraft for downlink to Earth. Meanwhile, the Flyby spacecraft used its two instruments to image the impact and then continued to photograph the comet as it followed its orbital path around the Sun. The primary science data was returned to Earth in near real-time, and all data was returned to Earth within 24 hours of the encounter. For the NASA Discovery-class Deep Impact mission, a two-part Deep Impact spacecraft was constructed: the Impactor spacecraft and the impact characterization (flyby) spacecraft, and an associated suite of surveillance instruments. These instruments included one high resolution visible imager, two identical medium-resolution visible imagers (one on the flyby and one on the Impactor) and one infrared spectrometer. The two-part spacecraft launched together in January 12, 2005 and separated on July 3 rd , 24 hours before reaching its Tempel 1 target. The Impactor separated from the flyby spacecraft and autonomously positioned itself directly in front of the encroaching Tempel 1 comet for a spectacular hypervelocity impact. This paper highlights portions of the article Deep Impact: Excavating Comet Tempel 1 written by the Deep Impact science team and published in Science as well as on-line by Science Express, 09/08/05.