The Hubble Space Telescope, one of the greatest scientific instruments of all time, is about to get an extreme makeover — an overhaul so delicate and risky that NASA astronaut John Grunsfeld likens it to "brain surgery."
At 19 years old, the famous telescope is showing its age. Three of its scientific instruments are broken. Half of its six gyroscopes, which keep the Hubble pointed in the right direction, aren't working. And its batteries are slowly dying.
The seven-member crew of space shuttle Atlantis is scheduled to blast off Monday in an attempt to fix it.
It will be the fifth, final and most difficult mission to service the Hubble — a mission that was judged so risky to astronauts it was canceled in 2004 before safety precautions were added to ease the concerns.
If the work succeeds, it will mean a glorious rebirth of the Hubble. The telescope would be 90 times more powerful than when it was launched in 1990. If the mission fails, astronomy's crown jewel could become a $6.9 billion "piece of space junk" with no chance to save it, astronaut and mission commander Scott Altman says.
No other flights to Hubble are planned. That's because the shuttle — the only vehicle that can reach the telescope — is 17 months from retirement.
There had always been the possibility of "another shot" at Hubble, says Mike Weiss, the telescope's deputy program manager.
That's no longer the case.
"This is the last opportunity," Weiss says. "There's no margin for error."
Even if Hubble were to blink off tomorrow, it would leave a legacy richer and more vast than that of any other astronomy tool. It has more discoveries to its credit than any other observatory, NASA's Jon Morse says.
It "has already earned its place in history as a triumph of science in our modern era," says Heidi Hammel, an astronomer at the Space Science Institute, a research institute. "Hubble brings the heavens down to us."
• Helped narrow the age of the universe to 12 billion to 14 billion years, rather than the 10 billion to 20 billion years known previously.
• Captured the farthest pictures of deep space ever taken, showing early galaxies born in the era when the first stars were forming.
• Detected exploding stars in a pattern that suggested a mysterious "dark energy" is propelling galaxies apart.
•Provided the first analysis of the atmosphere of planets in other solar systems and taken the first picture of such a planet.
For all those accomplishments, the Hubble's potential is perhaps even more tantalizing. The period after the mission will be "the grand finale of the Hubble symphony," says David Leckrone, Hubble project scientist at NASA.
"Everything we've done up to this point," he says, "has been in preparation for these final five years, where Hubble is at its peak of capability."
Viewing deep into space
Hubble's namesake is the late U.S. astronomer Edwin Hubble, who discovered that our galaxy is only one of countless others.
The observatory owes its scientific achievements mostly to one simple fact: It's out in space. Images snapped by telescopes on the ground are distorted by the Earth's atmosphere, as if they had been taken though a grimy windshield. Hubble sits comfortably above the atmosphere, offering a stunningly clear view of the universe.
That vantage point makes it possible for Hubble to produce pictures such as the famous Ultra Deep Field: a snapshot showing 10,000 galaxies, some not long after they emerged from the Big Bang.