Scientists call it one of the most important scientific instruments ever made by man, taking pictures of the universe that look back in time and show us how it looked billions of years ago.
So in January, many people were stunned when NASA Administrator Sean O'Keefe came to a conclusion that, in effect, condemned Hubble to a premature death. Correspondent Ed Bradley reports.
It was two years ago that the shuttle Columbia flew into space carrying a new camera to improve the Hubble space telescope's vision.
It was installed by astronauts making a "house call" to Hubble to service the telescope and upgrade its hardware.
"The amazing thing about these shuttle visits to Hubble is this concept of renewing it by using human space flight has worked out sensationally well," says Dr. Bruce Margon, the associate director of science for the Hubble space telescope.
"Each time Hubble has been visited in one of these missions, the new instruments not only make it almost as good as new but make it vastly more powerful."
Just how powerful was clear a few days ago when NASA unveiled a picture revealing 10,000 galaxies and showing the universe the way it looked near the dawn of time.
For the last two years, engineers have been making preparations for one final servicing mission -- to sharpen Hubble's vision and extend its life into the next decade. Without it, Hubble can't survive for more than a few years.
But in January, NASA cancelled that servicing mission. O'Keefe, NASA administrator, says his decision was because of last year's shuttle disaster, which made safety his primary concern: "While we might have gotten away with it, we might have gotten lucky. Lucky is not a management option, or a leadership option that I can buy into. We'll never eliminate the risks, but you sure can mitigate it as much as possible."
O'Keefe's decision – that a mission to Hubble was just too risky -- was based on a recommendation in last summer's report on the Columbia disaster.
If there's anyone who understands the risks, it's astronaut John Grunsfeld, an astronomer who has made two flights to Hubble and who is now NASA's chief scientist.
"I still think that Hubble is a tremendous resource and was worth risking my life for," says Grunsfeld. "But Columbia changed all of that in a very fundamental way. We now know more about the risks of the space shuttle than we ever knew before."
Does he think that flying to Hubble is more dangerous than flying to the space station?
"If everything goes perfectly on a mission, I would say it's comparable risk," says Grunsfeld. "But we've seen from Columbia that things don't always go perfectly. And it's that fundamental difference that on a Hubble flight if something goes wrong you run out of options very quickly. And on these space station flights we have lots of options."
O'Keefe's decision landed like a bombshell at the Space Telescope Science Institute in Baltimore, where Hubble's data is analyzed. What's the mood there been since?
"Many of our staff are still in shock, because these were Hubble's best years," says Margon. "It wasn't an issue of the declining years, but rather the years where Hubble was expected to do the very best science it ever would."
"People plan their life ahead of them," says Dr. Mario Livio, a senior scientist with the Hubble space telescope. "I mean, you have your scientific plans ahead of you, and then, just in one second, you know, all those plans are gone. So it's almost like a feel of, you know, when somebody's dying."
O'Keefe says he's not fond of the position he's in right now: "I'm not happy with the unpopularity of it. But nonetheless, it's a judgment call. and it's part of this responsibility I have and there is nothing in this that says you may only make decisions when they're popular."
In the scientific world, there has been an unprecedented storm of protest in reaction to O'Keefe's decision.
A "Save the Hubble" petition was launched on the Internet. Newspapers across the country have editorialized their support of Hubble and criticized O'Keefe's decision. And a congressional resolution was introduced calling for an opinion by "an independent panel of expert scientists and engineers."
Why is Hubble so important? "Hubble is truly the greatest instrument that ever was," says Livio.
The Hubble space telescope is the size of a Greyhound bus. It weighs 10 tons and flies 400 miles above the earth moving 5 miles a second. Its cameras and scientific instruments are so sophisticated that they can capture light that began traveling through space some 14 billion years ago.
By the time that light finally enters the telescope and is transformed into an image, the picture it shows is of the universe as it was back when the light began its journey in the unimaginably distant past -- answering questions that humans have pondered since the beginning of mankind.
What has it taught us about the history of the universe?
"Well, for one thing, how big is the place we live in? How old is the place we live in? That used to be the subject of furious arguments amongst astronomers," says Margon. "It's almost an obsolete question now. Hubble has solved that."
And then there are the pictures Hubble takes. The images are like nothing ever seen before -- as much art as science, visions of a universe more violent and fantastic than anyone had dared to imagine.
Images reveal everything from razor-sharp views of the planets in our own solar system to the vast stellar nurseries where stars and planets are born. Some show us the explosive outbursts of dying suns; others show the swirling masses of stars that make up the galaxies.
But Hubble hasn't just given us extraordinary pictures. It's helped astronomers determine that the age of the universe is some 14 billion years.
"Everyone is interested in their origins. It's a natural human yearning to sort of just look around and say, 'I wonder how that got there,'" says Margon. "We know how we came to be. I mean, how much more fundamental a self-quest can you imagine?"
In the last decade, Hubble's discoveries have revolutionized astronomy and astrophysics -- providing the deepest insights yet into the origins and the fate of the universe.
One of its most important contributions to science was nailing down the discovery that the expansion of the universe - that began with the Big Bang -is not slowing down.
Dr. Ed Weiler is the head of space science for NASA and the person in charge of the Hubble space telescope.
"Not only isn't the universe slowing down, it's speeding up," says Weiler. "It means that we don't understand gravity. This implies there's some negative energy force, some antigravity that's actually pushing things apart. We don't understand it. It's not supposed to be there."
Two years ago, Dr. Livio told us that the discovery that the expansion of the universe is accelerating is one of the most stunning and important discoveries in the history of science.
"Suppose I'll take my keys and I throw them up. They come back to my hand. Why did that happen? The gravity of the earth was able to slow these keys here, and then finally even reverse the motion," says Livio.
"So what we naturally thought was that this expansion ought to slow down, in the same way as these keys slowed down. What we discovered is that this expansion is in fact speeding up, accelerating. It would be like I throw these keys up, and instead of falling back into my hand, they actually speed up, upwards."
Scientists now believe that dark energy --- the force driving that acceleration -- accounts for more than 70 percent of everything in the universe. And they have no idea what it is.
"Hubble is absolutely the only telescope that can do that work, that can determine the nature of this dark energy," says Livio. "It's absolutely the only telescope that can do that."
Yet, if O'Keefe's cancellation of the next servicing mission to Hubble stands, that work will be disrupted.
President Bush spoke at NASA on Jan. 14: "The shuttle's chief purpose over the next several years will be to help finish assembly of the international space station."
He laid out his program to finish the international space station by 2010, and shift NASA's focus to returning astronauts to the moon and ultimately to Mars. Two days later, O'Keefe aborted the shuttle's trip to Hubble.
"The O'Keefe decision is irrevocable, and it's like surgery. If you're going to do an irrevocable decision, you want a second opinion. And that's why I asked for a second opinion -- on the risk factors," says Sen. Barbara Mikulski, who sits on the senate committee that controls NASA's budget.
"I believe that the decision was premature. The decision on the future of the Hubble must be done by a variety of expert opinions. We cannot cancel the Hubble, or decide the fate of the Hubble on the basis of one man's decision."
Without a major overhaul, engineers believe Hubble has a 50/50 chance of surviving another three and a half years.
They're trying to come up with ways to extend its life, but at some point, Hubble will fail. It will be a victim of old age and neglect, closing humanities most famous eye on the universe.
"If we don't go back to Hubble, we will have wasted an opportunity," says Mikulski. "And we will shut down a telescope of such stunning value, that if Galileo were alive, he would weep."
"Ask any person the name of a playwright. Most of them would say Shakespeare," says Livio. "Ask them the name of a scientist. Most of them would say Einstein. Ask the name of a telescope. They will all say Hubble."
On Thursday, NASA agreed to Sen. Mikulski's request for a second opinion. The National Academy of Sciences will examine the question of the future of Hubble.