Astronauts Prepare To Spruce Up Hubble Telescope Outdated Instruments To Be Replaced In Series Of Midnight Space Walks

As sleepless astronomers held their breath, two astronauts prepared late Thursday to start an exacting orbital house call on the $2 billion Hubble Space Telescope, culminating two years of painstaking rehearsals for one of the most demanding tasks in NASA’s manned space program.

In a six-hour spacewalk scheduled to end early today, the astronauts planned to replace two out-dated instruments in the bus-sized orbital telescope with more sophisticated sensors designed to dramatically improve its color vision and expand its ability to perceive infrared light.

The crew of the space shuttle Discovery, parked in orbit 370 miles above Earth, will conduct three more midnight spacewalks over the weekend to complete a $350 million refurbishment of NASA’s orbital eye, replacing vintage 1970s technology with the best the 1990s has to offer.

The new equipment will allow astronomers to stare with clearer, more discerning eyes at a universe of wonders, from the dense dust clouds in which stars and planets are born, to the voracious black holes devouring the hearts of many galaxies. “We’re salivating,” said one University of Michigan stargazer.

Later today, astronauts again will don their bulky white spacesuits, start deep-breathing their special oxygen mix and squeeze through Discovery’s airlock into the cargo bay for another six-hour, slow-motion ballet with the towering, 43-foot-high telescope, as the Earth speeds by below at 17,500 miles per hour.

Astronauts Gregory J. Harbaugh and Joseph R. Tanner plan to replace a failing guidance sensor with an $8 million device designed to ensure the telescope can stay aimed properly.

First they must install handrails and footrails to protect the instrument as they work. After wiggling the recorder into place, they must undo six bolts and 18 delicate electrical connectors, with fingers made stiff and clumsy by space gloves, to replace an engineering data recorder.

Drawing from a collection of 150 tools and crew aids especially designed for the mission, the crew will ratchet into place a variety of other upgrades on Saturday and Sunday, including protective lens caps and a grab-bag of new electronics. The shuttle also will nudge the observatory gently into a slighter higher orbit to extend its lifetime.

It is the second time in three years that NASA has launched a service mission to the Hubble. The telescope was designed to allow new instruments to be installed as old ones become obsolete. Two more servicing missions are planned to keep the telescope operational well into the next century.