Astronauts Swap Hubble Cameras in Swift Work

In the most crucial phase of the effort to restore the Hubble space telescope--and rectify one of NASA’s most embarrassing mistakes--astronauts late Monday installed a camera that will help the $1.5-billion observatory live up to its promise.

If a spacewalk planned tonight also goes as smoothly, the Hubble space telescope for the first time will have a clear, unobstructed view of the universe.

In the mission’s third arduous excursion outside the space shuttle this week, payload commander F. Story Musgrave and mission specialist Jeffrey A. Hoffman installed Monday night a $101-million camera built by the Jet Propulsion Laboratory. They worked so confidently that they kept almost an hour ahead of their schedule.

“Look at that baby,” said Hoffman as he unlimbered the new camera. “We’ll take some nice pictures with that.”

The new camera’s advanced sensors, among other things, will allow the Hubble to peer deeper into ultraviolet wavelengths hidden to astronomers on Earth and enable scientists to explore the origins of the cosmos.

Bouyed by the astronauts’ success so far, NASA officials said Monday that Endeavour’s seven-member crew has proved that people can service and rebuild satellites in orbit, validating an important idea underlying the design of the space station and other structures NASA hopes one day to maintain in space for decades.

“It is clear we can service the Hubble; we’ve now done it,” said Edward J. Weiler, Hubble project scientist at NASA’s Office of Space Sciences. “Now we have to see whether we can get the Hubble up to the telescope we promised the American people 3 1/2 years ago.

“Now we start fixing the science,” he said.

Astronauts Musgrave and Hoffman, making their second overnight spacewalk of the 11-day mission, gingerly unbolted the original camera, about the size of a baby grand piano, and parked it in the shuttle’s payload bay Monday evening for return to Earth. They then slid the 629-pound replacement camera into the empty service bay like a bureau drawer.

In the most crucial step, they delicately removed a bright red protective cover from the mirror that directs light from the telescope’s main beam into the camera. If they had accidentally touched the exposed mirror, they could have thrown the optics out of alignment or ruined its reflecting surface.

To preserve the camera’s pristine surfaces during assembly, engineers took extraordinary measures, said Larry Simmons, the JPL project manager who oversaw the camera’s design and construction. “We stopped paving roads (on the JPL campus) because we were worried about contamination. We stopped roofing buildings.”

Even before Hubble’s problems were apparent, NASA had intended to replace the original Wide-Field Planetary Camera, as the JPL instrument is called, with a more advanced model when the opportunity arose, to keep the telescope from becoming outmoded during its 15 years in space.

The corrections needed to compensate for the manufacturing flaws in the Hubble’s primary mirror, however, added $23.8 million to the camera’s cost, project officials said. To keep costs down, they also reduced by half the number of camera sensors designers could install.

Even so, the new camera system, which is really four cameras in one, will allow astronomers to examine the universe in unprecedented detail and offer the unique ability to explore the ultraviolet spectrum, JPL officials said.

“That is a big step for science because you simply cannot take ultraviolet images from the ground (because of atmospheric interference),” said Simmons.

While most Americans slept early Monday, mission specialists Kathryn C. Thornton and Thomas D. Akers replaced the 39-foot solar panels that supply the Hubble with electricity, talking each other through their checklists in a flow of amiable chatter.

One defective panel, twisted and bent during its 3 1/2 years in space, could not be rolled up for storage, a contingency mission planners had predicted and rehearsed. NASA flight directors abandoned plans to bring it back to Earth for study and told Thornton to jettison it overboard. As Endeavour passed into sunrise over southern Egypt, she stood on the end of the shuttle’s mechanical arm and carried the bent panel aloft and released it, dropping both hands at once in a flourish worthy of a circus rider.

Tumbling gently in Endeavour’s exhaust, the broad rectangular blanket of plastic began to flex, flapping like it had wings as it moved into the distance.

NASA officials watching from the Johnson Space Center were transfixed by the sight.

“There are images that are burned into your brain for your life,” said Hubble senior scientist David S. Leckrone of NASA’s Goddard Space Flight Center. “The mythic, Wagnerian image of Kathryn Thornton holding the solar array up toward the rising sun is something I’ll never forget.”

The only problems the two astronauts encountered during their six-hour and 36-minute spacewalk involved Thornton’s stopped-up ears and a temperamental suit radio.

“The solar arrays went on like a dream,” said Derek Eaton, Hubble program manager for the 13-nation European Space Agency, which designed and built the replacement panels. “I was thoroughly impressed with the whole thing. I feel thrilled to bits.”

Tonight’s Task: The COSTAR

Details of tonight’s spacewalk, sometime between 9 p.m. and 3 a.m. Pacific time.

Astronauts: Kathryn C. Thornton and Thomas D. Akers

Main Goal: Remove the high-speed photometer and replace it with COSTAR, the Corrective Optics Space Telescope Axial Replacement. This instrument contains corrective mirrors for three Hubble instruments.

Work Location: Toward the back (“bottom”) of the telescope, inside a set of double doors in the aft shroud.

Procedure: After unfastening four bolts to open the double doors to the service bay that will hold this instrument, the astronauts will loosen the latches holding the high-speed photometer in place and disconnect four electrical plugs and a ground wire. Using guide rails, they will slide the 487-pound, phone booth-size photometer out of the telescope and the mechanical arm will lower it into temporary storage. The astronaut standing in foot restraints on the end of the arm will then grab the 640-pound COSTAR in its cargo-bay container and hang on as the arm is raised and the instrument is lifted up. The mechanical-arm operator inside the shuttle will them maneuver the astronaut and COSTAR into place alongside the telescope and the spacewalkers will slide the instrument inside. The four electrical connections will then be reattached and the support latches secured. The service-bay door will then be closed and bolted shut, and the photometer will be placed in the cargo-bay container.

Where to watch: CNN and C-SPAN will offer live coverage.

Source: NASA