The Hubble Space Telescope was alive and well today after a pair of space-walking astronauts finished a risky repair job that NASA compared to a heart transplant.
"Hubble has a heartbeat," said NASA spokesman Mr Rob Navias, moments after the first streams of data arrived at ground stations.
Mission controllers were powering up and testing Hubble's systems one by one and were expected to be finished by mid-afternoon. All the systems so far had returned in good shape, and NASA managers said they expected the rest would be OK.
NASA managers had feared the operation to replace a faulty power control unit might have ended with Hubble no more than a costly piece of space junk if they could not restore power to the orbiting observatory.
It was not without drama, which included a leaking spacesuit, but NASA in the end had what it wanted - an orbiting observatory that may someday see to the very edge of the universe.
Astronauts Mr John Grunsfeld and Mr Rick Linnehan from the space shuttle Columbia had the difficult task of replacing the aging observatory's power control unit, a 160-pound box that distributes electricity to all the satellite's instruments and flight systems.
NASA had to turn off Hubble's power for the first time since it sat at the Kennedy Space Center in 1990 awaiting liftoff. Since satellites are rarely turned off after launch, and Hubble had never been turned off, NASA counted the mission among its most risky and challenging.
The old power unit was meant to be a permanent component, never to be handled 563 kilometres above Earth by men in bulky pressure suits, big white helmets and stiff, thick gloves.
"I can tell you there were a lot of people who thought we were crazy to even try it," said Mr Preston Burch, NASA's Hubble program manager.
Comparing the procedure to a heart transplant, Mr Dave Leckrone, the Hubble program scientist for NASA, said yesterday that major surgery entails a certain degree of risk.
Mr Linnehan had to disconnect most of the three dozen power couplings that led to various Hubble systems, much of the time using a special tool designed just for that job, since his gloved hand could not reach some of the cables and couplings.
Mr Grunsfeld had the job of installing the new system, which because of its size presented many of the same obstacles.
As the last of 36 connections were made to the new unit, a cheer went up in the Customer Service Room at Houston's Johnson Space Center, where some of Hubble's astronomers had gathered.
Preparations for the mission began in 1993, when power fluctuations were traced to a loose screw in the control unit.