— Some of the most distant galaxies ever seen appear in the Hubble Ultra Deep Field North, a portion of which is shown here. If a new servicing mission is approved, a new instrument called the Wide Field Camera 3 would spot galaxies even more distant, and therefore further back in time (Image: NASA/ESA/S Beckwith/HUDF team)
The Hubble Space Telescope will be able to see further back in time than ever before if it is fitted with two new instruments in a shuttle servicing mission.
Hubble needs new gyroscopes and batteries to keep it working properly. Its existing gyroscopes, which allow Hubble to point steadily at a target, could expire by 2008 and its batteries could die by 2010.
NASA is considering sending astronauts on a space shuttle mission to replace these parts in early 2008. A decision is expected to be announced at 1000 EST (1500 GMT) on Tuesday (see Hubble's fate being decided by NASA).
A servicing mission would not only extend Hubble's lifetime to at least 2013 but would also see two powerful new instruments installed that would give Hubble unprecedented abilities.
One, called the Wide Field Camera 3 (WFC3), can see a broad range of wavelengths including ultraviolet, visible and infrared and should be especially useful in studying the early universe. To make room for it, the Wide Field Planetary Camera 2, which was installed on Hubble in 1993, would be removed.
WFC3's sensitivity and wide field of view would make it 15 to 20 times more efficient at searching for faint, distant galaxies than Hubble's Near Infrared Camera and Multi-Object Spectrometer (NICMOS), which has previously been used for this sort of work.
That would allow it to see fainter, more distant and more ancient objects than any previous Hubble instrument. Currently, there is tentative evidence it has observed objects that appear as they were about 800 million years after the big bang, says Hubble scientist Malcolm Niedner of NASA's Goddard space Flight Center in Greenbelt, Maryland, US.
"With WFC3 all this would be a lot more definitive and crisper and in much greater numbers," he told New Scientist.
WFC3 would also be useful for trying to understand what caused primordial hydrogen gas to be stripped of its electrons early in the universe's history in a process called reionisation. This crucial turning point made the universe more transparent to light and affected the growth of early galaxies.
"The WFC3 infrared channel would be just the right instrument for this investigation and, in fact, perhaps the only way of studying the end of reionisation until the James Webb Space Telescope is launched in 2013," says Massimo Stiavelli of the Space Telescope Science Institute in Baltimore, Maryland, US.
The second instrument that would be installed, called the Cosmic Origins Spectrograph (COS), would measure the light spectrum of objects at ultraviolet wavelengths.
It would restore some abilities lost when Hubble's Space Telescope Imaging Spectrograph (STIS) stopped working in 2004 (see Shelved instrument could restore Hubble's UV vision).
COS would be especially useful for studying the gas that floats between galaxies, Niedner says. This would help astronomers survey the diffuse gas in space and understand how star formation and supernovae have affected it. The instrument would also help astronomers study developing stars.
Martin Barstow, an astronomer at the University of Leicester, UK, and a member of Hubble's user committee, says a servicing mission would give Hubble "a dramatic new lease on life".
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