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Emily LakdawallaAugust 10, 2007

Phoenix and New Horizons updates

The Phoenix spacecraft, which launched a week ago, has just successfully accomplished its first and largest trajectory correction maneuver. When they are launched, Mars spacecraft are intentionally targeted to miss Mars by a substantial margin, to make sure that the launch vehicle's third stage -- which is traveling on the same trajectory as the spacecraft, just a bit behind it -- cannot possibly crash onto Mars. This allows space agencies to avoid the rigorous sterilization procedures that are necessary to prevent Earth critters from hitching a ride to Mars when spacecraft land there, either intentionally (as in the case of Phoenix) or unintentionally (as in the case of Mars Climate Orbiter). Phoenix' launch trajectory was biased away from Mars by nearly a million kilometers. This trajectory correction maneuver (commonly abbreviated as "TCM") and another one scheduled for mid-October will correctly target Phoenix for its Mars arrival on May 25, 2008. You can watch Phoenix' progress on JPL's Solar System Simulator, which currently defaults to a view of Phoenix' course.New Horizons apparently had a difficult week, but all is okay now. According to Principal Investigator Alan Stern, the spacecraft transmitted its first "red" (as opposed to "green") beacon during a routine check-in, which appears to have resulted from a reset of a command and data handling computer. With additional time on the Deep Space Network and a lot of lost sleep the team managed to return the spacecraft to its nominal hibernation state early this morning. These kinds of events will happen from time to time on long missions, and it's good that the team recovered so quickly; but it will be better once the team figures out why the reset happened in the first place and how to prevent it from happening again in the future.

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Emily Lakdawalla

Senior Editor and Planetary Evangelist for The Planetary Society
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