NASA's Stardust-NExT mission spacecraft is within a quarter-million miles (402,336 kilometers) of its quarry, comet Tempel 1, which it will fly by tonight. The spacecraft is cutting the distance with the comet at a rate of about 10.9 kilometers per second (6.77 miles per second or 24,000 mph).
The flyby of Tempel 1 will give scientists an opportunity to look for changes on the comet's surface since it was visited by NASA's Deep Impact spacecraft in July 2005. Since then, Tempel 1 has completed one orbit of the sun, and scientists are looking forward to discovering any differences in the comet.
The closest approach is expected tonight at approximately 8:40 p.m. PST (11:40 p.m. EST).
During the encounter phase, the spacecraft will carry out many important milestones in short order and automatically, as the spacecraft is too far away to receive timely updates from Earth. These milestones include turning the spacecraft to point its protective shields between it and the anticipated direction from which cometary particles would approach. Another milestone will occur at about four minutes to closest approach, when the spacecraft will begin science imaging of the comet's nucleus.
The nominal imaging sequence will run for about eight minutes. The spacecraft's onboard memory is limited to 72 high-resolution images, so the imaging will be most closely spaced around the time of closest approach for best-resolution coverage of Tempel 1's nucleus. At the time of closest encounter, the spacecraft is expected to be approximately 200 kilometers (124 miles) from the comet's nucleus.
The mission team expects to begin receiving images on the ground starting at around midnight PST. Transmission of each image will take about 15 minutes. It will take about 10 hours to complete the transmission of all images and science data aboard the spacecraft.
Live coverage on NASA TV and via the Internet begins at 8:30 p.m. PST from mission control at NASA's Jet Propulsion Laboratory in Pasadena, Calif. Coverage also will include segments from the Lockheed Martin Space System's mission support area in Denver. A post-flyby news conference is planned on Feb. 15 at 10 a.m. PST .
The live coverage and news conference will also be carried on one of JPL's Ustream channels. During events, viewers can take part in a real-time chat and submit questions to the Stardust-NExT team at: http://www.ustream.tv/user/NASAJPL2 .
During its 12 years in space, Stardust became the first spacecraft to collect samples of a comet , which were delivered to Earth in 2006 for study. The Stardust-NExT mission is managed by JPL for NASA's Science Mission Directorate in Washington. Lockheed Martin Space Systems in Denver built the spacecraft and manages day-to-day mission operations.