[FPSPACE] Dawn Journal for March 28, 2010
ljk4 at msn.com
Tue Mar 30 03:21:56 EDT 2010
March 28, 2010
Dawn continues patiently forging through the asteroid belt, its permanent residence, as it climbs away from Earth and the Sun. Having thrust with its ion propulsion system for more than 1.5 years, the spacecraft remains healthy and on target for its rendezvous with alien worlds.
Our interplanetary adventurer still has a great deal of ion thrusting to complete before it can begin its orbital exploration of Vesta next year. Although it will suspend thrusting for a few weeks this summer to conduct some special activities (to follow along, be sure to renew your subscription to these logs the first time our helpfully persistent telemarketers call), it will devote most of the time until early August 2011 in powered flight, continuously reshaping its orbit around the Sun.
In addition to keeping the ship sailing smoothly and on course, Dawn’s engineers (who reside and work on distant Earth) are developing the detailed instructions that will guide it into orbit around Vesta and throughout its year of operations there. This process began last month and will continue even as the probe begins executing the first of the commands in May 2011.
Mission controllers compile Dawn’s instructions by assigning a time to each individual command. Groups of these timed commands are known as a “sequence.” During the current interplanetary cruise phase of the mission, sequences generally extend for 5 weeks, but some special activities may use sequences as short as a few hours. Usually more than one sequence is executing at a time, but like all the instruments in an orchestra, they are carefully synchronized and coordinated so the overall score accomplishes the composer’s artistic intent.
Readers may recall that the mission is separated into phases. Following the “launch phase” was the 80-day “checkout phase”. The current “interplanetary cruise phase,” which began on December 17, 2007, is the longest. It ends when the “Vesta phase” begins.
(Other phases may occur simultaneously with those phases, such as the “oh man, this is so cool phase,” the “what clever name are we going to give this phase phase,” and the “lunch phase.”) Because the mission at Vesta is so complex, it is further divided into sub-phases. The Vesta sequences that are being developed now are for the “approach phase.”
Approach begins in early May 2011 and concludes 3 months later when Dawn has maneuvered to the first orbit from which it will conduct intensive science observations, known as survey orbit.
Full journal entry here:
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