Dawn shuts off motor, will encounter Mars soon

Saturday, November 22, 2008

Dawn just finished thrusting to it's right at that red mark on the map. After the encounter with Mars it'll have one more orbit around the sun before arriving at the first real target, Vesta.

All is good with Dawn, NASA's most exciting probe at the moment. It has just shut off its motor ahead of an encounter with Mars, and then after that there'll be some more thrusting for half an orbit or so after which it will make its way to an encounter with Vesta in August 2011. Vesta is going to be extremely interesting in being the largest asteroid to be encountered for such a long period of time, but Ceres is the real prize as it seems to be a good target for human colonization as well. Here's part of the press release:

NASA's Dawn spacecraft shut down its ion propulsion system today as scheduled. The spacecraft is now gliding toward a Mars flyby in February of next year.

"Dawn has completed the thrusting it needs to use Mars for a gravity assist to help get us to Vesta," said Marc Rayman, Dawn's chief engineer, of NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Dawn will now coast in its orbit around the sun for the next half a year before we again fire up the ion propulsion system to continue our journey to the asteroid belt."


Dawn's ion engines are vital to the success of the misson's 8-year, 4.9-billion-kilometer (3-billion-mile) journey to asteroid Vesta and dwarf planet Ceres. One of these extremely frugal powerhouses can generate more than 24 hours of thrusting while consuming about .26 kilograms (about 9 ounces) of the spacecraft's xenon fuel supply -- less than the contents of a can of soda. Over their lifetime, Dawn's three ion propulsion engines will fire cumulatively for about 50,000 hours (over five years) -- a record for spacecraft.

Dawn will begin its exploration of asteroid Vesta in 2011 and the dwarf planet Ceres in 2015. These two icons of the asteroid belt have been witness to so much of our solar system's history. By utilizing the same set of instruments at two separate destinations, scientists can more accurately formulate comparisons and contrasts. Dawn's science instrument suite will measure shape, surface topography, tectonic history, elemental and mineral composition, and will seek out water-bearing minerals. In addition, the Dawn spacecraft itself and how it orbits both Vesta and Ceres will be used to measure the celestial bodies' masses and gravity fields.
Here are the two next to the Moon for comparison:


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