Astronauts aboard the Space Shuttle Columbia have successfully completed all their planned repairs and upgrades to the Hubble Space Telescope. The orbiting observatory now has more electrical power and more discovery power than at any time since its launch 12 years ago.
For astronomers, the climax of this fourth Hubble house call was the installation on Thursday of the Advanced Camera for Surveys (ACS), a state-of-the-art imager with a wider field of view and higher sensitivity than any of the telescope's earlier instruments. To make room for the ACS, space-walkers James Newman and Michael Massimino first removed the Faint Object Camera (FOC), the last component of Hubble's original scientific arsenal.
During three earlier space walks, Columbia's crew replaced Hubble's twin solar-cell arrays and the power control unit that distributes electricity to the observatory's systems. For this latter task, the telescope had to be shut off completely, something that hadn't been done since it reached orbit in April 1990. Fortunately everything went according to plan. With its new solar arrays and electronics, Hubble now has some 30 percent more power than before enough to operate several scientific instruments at once.
On the mission's fifth and final space walk, carried out earlier today, John Grunsfeld and James Newman restored the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) to operation by hooking up a new cooling system. Installed during the second servicing mission in 1997 and intended to last at least five years, NICMOS ran into problems and depleted its original supply of cryogenics in less than half that time. With the new cooler, the instrument should once again be able to make observations of high-redshift galaxies, cool stars, and dusty nebulae.
Once Grunsfeld and Newman were safely back inside Columbia, commander Scott Altman and pilot Duane Carey raised the shuttle's and the telescope's orbit by about 6 kilometers (3.7 miles). Robotic-arm operator Nancy Currie is scheduled to release Hubble back into free flight on Saturday. The first images from the new ACS and revitalized NICMOS should be available within a few weeks.