Dawn finishes Mars phase
Fri Feb 27, 2009 at 08:17 UTC
With Mars disappearing in its metaphorical rearview mirror, NASA's Dawn spacecraft's next stop is the asteroid belt and the giant asteroid Vesta. Dawn got as close as 549 kilometers (341 miles) to the Red Planet during its Tuesday, Feb. 17, flyby.
Dawn's navigators placed the spacecraft on a close approach trajectory with Mars so the planet's gravitational influence would provide a kick to the spacecraft's velocity. If Dawn had to perform these orbital adjustments on its own, with no Mars gravitational deflection, the spacecraft would have had to fire up its engines and change velocity by more than 9,330 kilometers per hour (5,800 miles per hour).
The achieved goal of the flyby was to obtain this orbital pick-me-up, making possible its voyage to asteroid Vesta and, later, the dwarf planet Ceres. But Dawn's science teams used this massive target of opportunity to also perform calibrations of some of the scientific instruments. Calibration images were taken by Dawn's framing camera, and the Gamma Ray and Neutron Detector also observed Mars for calibration. These data will be compared to similar observations taken by spacecraft orbiting Mars.
Further observations were planned during the flyby, but fault detection software canceled the data collection and put the spacecraft into safe mode, a limited-activity precautionary status. The cause was determined to be an inappropriate software response to an expected temporary loss of valid data from the spacecraft's star tracker in the vicinity of Mars, and engineers were able to restore the spacecraft to normal operations within 48 hours.
While the spacecraft will never be back in the vicinity of Mars again, the Dawn team is using the event to fine-tune its software.
The spacecraft has already traveled about 1.8 million kilometers (1.1 million miles) beyond Mars. It has 30 months and 1.8 billion kilometers (1.1 billion miles) to go before its rendezvous with Vesta in 2011.
Credit: NASA/JPL/MPS/DLR/IDA, and the Dawn Flight Team
This near-infrared image from the framing camera on NASA's Dawn spacecraft was taken near the point of closest approach to Mars on Feb. 17, 2009, during Dawn's gravity assist flyby. The image, taken for calibration purposes, shows a portion of the fretted and cratered northwest margin of Tempe Terra, Mars. The scarp of the highlands/ lowlands boundary is illuminated by the light of dawn, and traces of fog appear in the lower portion. The area covered by the image is about 55 kilometers (34 miles) across.
| Source: Jet Propulsion Laboratory | |
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