Post by Chicago Astronomer - Astro Joe on Jan 23, 2007 22:18:36 GMT -6
Repairing The Hubble one last time
Time is running out for Hubble. The batteries are nearly depleted, its steer-controlling gyroscopes are shutting down one-by-one and the wear and tear from years in space is taking its toll. Without some serious TLC—tasks slated in the proposed service mission—Hubble might cease to function as a science instrument anytime in the next year or two. Eventually, without installation of a mechanism to bring the telescope back to Earth safely it would spin out of control.
Over a series of five spacewalks, astronauts will complete nuts-and-bolts work to keep Hubble alive.
They will also install two new instruments: the Wide Field Camera 3, which has visible, near-UV and near-infrared capabilities; and the Cosmic Origins Spectrograph (COS), which will use ultraviolet vision to study the formation and evolution of galaxies and ultimately how the universe’s structure has changed over time.
For Grunsfeld, the most significant and trickiest task will be to revive the Space Telescope Imaging Spectrograph (STIS), which conked out after a power failure in August 2003.
Installed on Hubble in February 1997, the STIS separates incoming light into its constituent colors, giving astronomers a chemical map of a distant object. Since deployed, STIS has been critical in the confirmation of black holes at the centers of galaxies, made the only discovery of an atmosphere around an exoplanet and helped confirm the age of the universe.
The repair job would typically be completed in a clean room, where mechanics would don sterile garbs and be equipped with tiny screwdrivers. The instrument is too bulky to even move it into the shuttle for repairs.
“The first problem is that the power supplies are deep in the instrument and behind covers," Grunsfeld said. "If we could take STIS out of Hubble and bring it to the shuttle it would be relatively straightforward, but you can’t do that."
The most optimal power supply for replacement is beneath a cover plate mounted to the instrument with more than 100 tiny screws and washers. “And that’s the kind of thing we have no capability to do with the current set of tools," he said. "So we’ve developed a new power tool— a mini power screwdriver—and ways of grabbing these screws so they don’t get loose inside the telescope, which could be disastrous."
Once this sweat-dripping operation is complete, the astronaut can change out the power-supply card—and the real fun begins.
“The card has 300 or so tiny gold pins on the back for replacement that we have to slide in. But you can’t really see it because we have on these huge bubble helmets. You can’t get your head in there with a tiny flashlight. So it’s going to be hard,” he said.
Grunsfeld and other service team members have practiced the repairs for hours and hours in a simulated environment. With a background in ballooning, Grunsfeld said he has experience reaching into instruments and completing repairs like this one without stereo vision.
Source: www.space.com/scienceastronomy/070123_hubble_hugger.html
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I wish it were sooner, but ok...
