How do you stop a spacecraft traveling at 47,500 mph? Well if you're NASA you fire its rockets and that's exactly what the space agency did this week to slow down its Stardust satellite to ultimately let it snap better pictures of the Tempel 1 comet it will pass by next year.
NASA this week said Stardust-NeXT fired its engines for 22 minutes 53 seconds on Feb. 17 to purposely delay its arrival at comet Tempel 1 by 8 hours 21 minutes, altering the spacecraft's speed by 54 miles per hour. The spacecraft's velocity relative to the sun is 47,500 mph, NASA said.
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The Lockheed Martin-built spacecraft will still fly by the comet on Feb. 14, 2011, Valentines' Day but hopefully the delay will let the satellite get better high-resolution images of the comet.
NASA said that's important because the comet rotates, allowing different regions of the comet to be illuminated by the sun's rays at different times. Mission scientists want to maximize the probability that areas of interest previously photographed by NASA's Deep Impact Deep Impact mission in 2005 will also be covered by the sun's rays and visible to Stardust's camera when it passes by.
According to the NASA, the comet's surface features three pockets of thin ice. The area the ice covers is small. The surface area of Tempel is roughly 45 square miles or 1.2 billion square feet. The ice, however, covers roughly 300,000 square feet. And only 6% of that area consists of pure water ice. The rest is dust.
Along with new high-resolution images of the comet's surface, Stardust-NExT will also measure the composition, size distribution, and flux of dust emitted into the coma, and provide new information on how Jupiter family comets evolve and how they formed 4.6 billion years ago, NASA said.
NASA launched the satellite on Feb. 7, 1999 and it was the first spacecraft in history to collect samples from a comet and return them to Earth for study. While its sample return capsule parachuted to Earth in January 2006, mission controllers were placing the still viable spacecraft on a trajectory that would let NASA the re-use the already-proven flight system if a target of opportunity presented itself, NASA said.
In January 2007, NASA re-christened the mission "Stardust-NExT" (New Exploration of Tempel), and the Stardust team began a four-and-a-half year journey to comet Tempel 1. This will be humanity's second exploration of the comet - and the first time a comet has been "re-visited," NASA stated.
The spacecraft has completed it 4,000th days of flight and traveled approximately 3.4 billion miles since its launch.
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