In an orbital first, astronauts opened up and installed new electronics on one of the Hubble Space Telescope鈥檚 most important instruments on Saturday. But NASA must now wait for the results of a battery of tests to see if the ambitious repair job was a success.
The space shuttle Atlantis is currently orbiting Earth on an 11-day mission to refurbish Hubble and extend its life until at least 2014. This is the fifth and last mission to service the telescope, which NASA hopes will leave Hubble with its best vision yet.
After two days of spacewalks that ran over-schedule, astronauts John Grunsfeld and Andrew Feustel made short work of the repair of Hubble鈥檚 Advanced Camera for Surveys (ACS), expected to be one of the most challenging tasks of the mission.
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The instrument, which is actually a set of three cameras, or 鈥渃hannels鈥, was one of Hubble鈥檚 most widely-used devices, producing some of the telescope鈥檚 most breathtaking images. But a series of electrical problems in 2006 and 2007 left it with just one working channel, sensitive to ultraviolet light.
The ACS was not designed to be repaired in orbit. To access the camera鈥檚 interior, Grunsfeld had to use specialised tools to cut through a screen-like grid protecting the instrument and remove 32 screws to open a face plate. Once inside, Grunsfeld removed four circuit boards and installed a specially-designed electronics box and an external power supply.
Iconic images
If the repair proves successful, it should restore the camera鈥檚 wide-field channel, used for survey work. This is responsible for some of Hubble鈥檚 most iconic images, including the Ultra-Deep Field, the deepest visible-light image of the universe yet taken, which revealed galaxies as they were just 700 million years after the big bang.
NASA hopes that the new electronics will also indirectly restore the camera鈥檚 high-resolution channel, used for more detailed pictures with a narrower field of view.
鈥淚t simply couldn鈥檛 have gone more smoothly,鈥 Hubble senior scientist David Leckrone told reporters on Saturday. 鈥淲e have demonstrated the very first internal repair of a scientific instrument in space today.鈥
鈥淭his was an instrument that was dead and it has now been demonstrated to be alive, at least electrically,鈥 Leckrone continued. But the ACS must undergo four hours of tests this evening before the repair can be declared a success.
Glasses removed
Before beginning the sensitive repair work, Grunsfeld and Feustel removed Hubble鈥檚 corrective 鈥済lasses鈥, a set of lenses installed in 1993 to counteract blurring created by Hubble鈥檚 misshapen primary mirror. All of the instruments on Hubble now have built-in corrective optics to counteract the flaw, so the device is no longer needed.
In its place, the astronauts installed a new instrument called the . It can measure the spectrum of objects at ultraviolet wavelengths, revealing more about the diffuse gas that floats between galaxies and the web-like distribution of matter in the universe.
On Sunday, astronauts Mike Massimino and Michael Good will attempt to repair the Space Telescope Imaging Spectrograph (STIS) which failed in 2004.
