Nasa Messenger Spacecraft To Become 1St Spacecraft To Orbit Mercury Tonight
After more than a dozen laps through the inner solar system, NASA's MESSENGER spacecraft will move into orbit around Mercury on March 17, 2011. The durable spacecraft - carrying seven science instruments and fortified against the blistering environs near the sun - will be the first to orbit the innermost planet. At 8:45 p.m. EDT, MESSENGER - having pointed its largest thruster very close to the direction of travel - will fire that thruster for nearly 14 minutes, with other thrusters firing for an additional minute, slowing the spacecraft by 862 meters per second (1,929 mph).

The orbit insertion will place the spacecraft into a 12 hour orbit about Mercury with a 200 kilometer (124 mile) minimum altitude. At the time of orbit insertion, MESSENGER will be 46.14 million kilometers (28.67 million miles) from the sun and 155.06 million kilometers (96.35 million miles) from Earth.

MESSENGER has been on a 6.6 year mission to become the first spacecraft to orbit Mercury. The spacecraft followed a path through the inner solar system, including one flyby of Earth, two flybys of Venus, and three flybys of Mercury. This impressive journey is returning the first new spacecraft data from Mercury since the Mariner 10 mission over 30 years ago.

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