Coutdown... 10,9,8,....
by Jim Fanson, Kepler, JPL Project Manager
All of the technical and programmatic reviews leading to the release of the dust cover from Kepler are now successfully completed. This has resulted in formal approval from NASA Headquarters to release the cover.
The project team will spend the day today ensuring that all final planned work is complete and that no new issues have arisen following the formal reviews that have been convened. If everything checks out, the team will begin the procedure to release the cover, which will occur no earlier than about 6:30 p.m. Pacific Time this evening (April 7), with a backup opportunity tomorrow evening.
The spacecraft will be maneuvered into the proper orientation so that the cover, when released, will enter an orbit that will never take it into the field of view of the telescope. When this maneuver is complete, reaction control thruster firings will remove momentum stored in the reaction wheels. This will reduce the wheel speeds to a low level so that they will be able to absorb the momentum imparted when the cover is released.
NASA's Deep Space Network will establish communication with the spacecraft using three large communication antennas in Goldstone, Calif., and Madrid, Spain. The navigation team will prepare to track the motion of the spacecraft using radio-frequency Doppler shifts. The operations team will then send a command to the spacecraft to send a current pulse through a burn-wire in the cover latch release mechanism, and the cover will spring free of the spacecraft. Telemetry from the spacecraft will independently confirm the motion of the cover. At that point, starlight will enter the telescope for the first time, and engineers will begin the process of evaluating the star images and collecting further calibration data.
und hier eine Animation dazu:
This artist's animation illustrates how the dust cover on NASA's Kepler telescope will be ejected. Engineers will send a command up to the space telescope to pass an electrical current through a "burn wire." The burn wire will break and a latch holding the cover closed will be released. The spring-loaded cover will swing open on a fly-away hinge, before drifting away from the spacecraft and entering its own orbit around the sun. (Kepler is also orbiting the sun in what's called an Earth-trailing orbit.)
With the cover off, starlight will enter Kepler's science instrument, the photometer, and be imaged onto its focal plane. Engineers will continue to calibrate the instrument using images of stars for another several weeks, after which science observations will begin.
Image credit: NASA/Ames/JPL-Caltech
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Low resolution animation (7MB mov)
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