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ASTRONOMERS and telescope builders have come up with a plan to give the
ageing Hubble Space Telescope a new lease of life. Instead of building an
entirely new space telescope, they propose sending up just huge mirrors, and
then letting Hubble look through them.

According to Jim Crocker of Johns Hopkins University in Baltimore, a
feasibility study has shown that it is possible to turn the 2.4-metre Hubble
into a giant 8-metre space observatory. 鈥淭he cost will be some $250
million,鈥� says Crocker, 鈥渓ess than half the cost of building a new space
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The idea was proposed by Bob Woodruff of Ball Aerospace and Roger Angel of
the University of Arizona in Tucson. At first, Crocker recalls, it sounded
鈥渞idiculous鈥�. But a study group of more than 20 engineers, set up by Crocker,
found no obvious show-stoppers. 鈥淭hese people have a lot of experience with
Hubble,鈥� says Crocker. 鈥淚f they say it can be done, you can鈥檛 dismiss that
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An upgraded Hubble would be able to see planets orbiting nearby
stars鈥攃urrently these can only be detected indirectly鈥攁nd search for
signs of oxygen in their atmospheres. Also, with 10 times as much sensitivity
and a fourfold improvement in resolution, the new Hubble could peer back in
space and time to the era before the first galaxies were born. 鈥淭he science case
is pretty compelling,鈥� says Crocker.

To build the 8-metre telescope, the team proposes using a spare mirror
鈥渂lank鈥� left over from building the European Southern Observatory鈥檚 four-mirror
Very Large Telescope. After polishing the parabolic surface, the back would be
ground away to leave a meniscus-shaped mirror only 2 millimetres thick and
weighing less than 1 tonne. Five thousand actuators on its back would control
the shape of the ultra-thin mirror. For launch, it would be cut in three, stowed
in the cargo bay of the space shuttle, and installed during a number of
spacewalks. Astronaut consultants say the job is feasible, and the mirror could
be launched as early as 2006.

But in a recent report from the US National Research Council on astronomy
priorities for the next decade, a review committee led by Joe Taylor of
Princeton University, New Jersey, and Chris McKee of the University of
California in Berkeley says it has 鈥渘ot recommended any new moderate or major
missions for space-based ultraviolet or optical astronomy for the coming
decade鈥�. The main reason is that infrared wavelengths offer greater research
opportunities and these wavelengths will be well covered by the Next Generation
Space Telescope, a $500 million observatory with an 8-metre mirror due
for launch in 2009 or 2010.

鈥淭he idea is very smart and the team that proposes it has to be taken
seriously,鈥� says Piero Benvenuti, director of the Space Telescope European
Coordinating Facility in Garching, Germany. 鈥淏ut given the current budget
situation, both in the US and Europe, I think it will remain an excellent and
technically extremely interesting academic exercise.鈥�