[FPSPACE] Dawn Journal for November 26, 2008
ljk4 at msn.com
Wed Nov 26 22:14:19 EST 2008
November 26, 2008
Dear Indawnviduals, The Dawn spacecraft is healthy and on course for its flyby of Mars early next year. The planet’s gravity will help boost the probe on its way to rendezvous with Vesta. While the spacecraft has its sights set on the asteroid belt (via Mars), its path is now bringing it closer to Earth. Meanwhile, from Earth’s perspective, Dawn appears to be approaching a blindingly close encounter with the Sun. With so much happening in the solar system, all readers, whether local or not, are invited to turn their attention here. In the last log, we saw that Dawn was nearing the end of an extended period of thrusting with is ion propulsion system that began on December 17, 2007. When it left Earth on September 27, 2007, the Delta II rocket deposited the spacecraft into a carefully chosen orbit around the Sun. By October 31, 2008, the spacecraft had completed the thrusting it needed to change that orbit so it would encounter Mars at just the right time, location, and angle to sling it on its way to Vesta. During this interplanetary cruise phase, Dawn thrust for 270 days, or 85% of the time. Expending less than 72 kilograms (158 pounds) of xenon propellant, the spacecraft changed its speed by about 1.81 kilometers per second (4050 miles per hour). Although controlling an interplanetary probe across hundreds of millions of kilometers (or miles) of deep space and guiding it accurately enough to reach its remote destination seems as if it should be a very simple task, readers may be surprised to know that it is not. Let’s consider just one aspect of the problem.
Full entry here:
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