Trace the space telescope's triumphs and setbacks, as described by the experts most familiar with Hubble's history.
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Hubble telescope's highs and lows
The Hubble Space Telescope has circled Earth once every 97 minutes since it was launched in 1990, peering into deep space and sending back digital postcards that have wowed the world. But it hasn't always been smooth sailing for the world's best-known eye in the sky. Click through this slideshow to learn about the space telescope's highs and lows, as described by the experts most familiar with Hubble's history.
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A long road
After decades of dreaming and technical planning, and years of political debates over budgets and schedules, the shuttle Discovery released the Hubble Space Telescope into orbit on April 25, 1990. The deployment came 12 years after Congress approved funding for the telescope and four years after the Challenger explosion, which dealt a huge setback to NASA and the Hubble project. "You had to sit and wait years to do something you were about ready to do," said David Leckrone, NASA's senior project scientist for the Hubble Space Telescope. "You had to postpone gratification."
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A flawed mirror on a serviceable telescope
A few months after Hubble was delivered, astronomers realized the "telescope didn't work well," Leckrone said. "It had a flaw in the optics - and that, of course, was everybody's deepest valley." But Hubble was designed to be fixed in orbit, and in 1993 astronauts installed a new camera and corrective optics that compensated for the flaws. "That was a high, high peak, maybe the highest peak in all Hubble history," Leckrone said. The fixes unlocked Hubble's full potential, as shown in this before-and-after image of the galaxy M100.
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Eagle Nebula wins hearts
Even before the corrective optics were installed, "Hubble revolutionized the way we do astronomy and revolutionized the role of astronomy in culture," said David DeVorkin, a senior curator in the space history division at the Smithsonian Institution in Washington. The revolution kicked into high gear with the 1995 release of this image of three pillarlike structures in the Eagle Nebula, said Robert Smith, a historian of science and technology at the University of Alberta. Hubble's wildly popular images turned it into "the people's telescope," he said.
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Seeing galaxies far, far away
For 10 days in December 1995, Hubble's mirror was trained on a speck of sky to gain a view on the farthest reaches of the visible universe. The Hubble Deep Field shed light on the formation of galaxies. "It really started showing the galaxies were built by accretion, from little bits to bigger bits to bigger and bigger and bigger," DeVorkin said. Smith noted that Hubble has continued to make deep field images, "but that first one shows the kind of thing that could be done. And so that was a very important event for the telescope."
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Hubble helps determine the age of the universe
In the late 1990s, Hubble's observations of distant supernovae led astronomers to realize that the expansion of the universe has not slowed down since the big bang. "That was the complete shock," Leckrone said. The finding helped astronomers determine that the expansion is accelerating. The Hubble observations produced an estimate of around 13 billion years for the age of the universe. Later, another space telescope, the Wilkinson Microwave Anisotropy Probe, narrowed down that estimate to 13.7 billion years.
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Instrument makes discovery, then dies
In 2001, an astronomer using Hubble's spectrograph, which measures the properties of light, detected the telltale signature of sodium in the atmosphere of a planet in orbit around a distant star. This artist's rendering shows the hot Jupiterlike planet around its star, HD 209458. It was the first step down a long path that scientists hope will lead to the detection of signs of life in the atmosphere of an Earthlike planet around another star. A few weeks after the discovery, the spectrograph broke. "The timing was just awful, but at least we got the one case," Leckrone said.
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Disaster strikes
On Feb. 1, 2003, the shuttle Columbia disintegrated during re-entry, killing all seven astronauts aboard. The tragedy came as a heavy blow to NASA, and one of the consequences was that a long-planned final service call to Hubble was canceled. The main concern was safety: Shuttle astronauts lacked a backup rescue plan should they run into trouble. "It was deep, deep depression," Leckrone said, "stacked on top of the normal depression that would come from the loss of a crew and a shuttle and the tragedy of that, that makes everybody mourn. And then to have this piled on top of it - it just didn't seem rational."
— Robert Mccullough / 2003 THE DALLAS MORNING NEWS
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The dark side
Hubble's Advanced Camera for Surveys, installed in 2002, has shown how a substance called dark matter distorts the light of distant galaxies. Astronomers combined Hubble's power with the Chandra X-ray Observatory's imagery to make this image of a collision between two galaxy clusters in 2006. "The ordinary matter (mostly hydrogen and helium gas) piles up, but the dark matter doesn't do anything except it keeps going," Leckrone said. Dark matter is the blue stuff on either side of the galaxies. Astronomers say this image ranks among the best evidence for dark matter's existence.
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Course change: All systems go
Leckrone and his colleagues were not the only people upset by NASA's decision to cancel the final servicing mission to Hubble. With images such as the Pillars of Creation in mind, the public rallied to save the telescope. "I don't think it would have happened had there not been this series of spectacular images," Smith said. "We got our mission back, and so that was a high," Leckrone said. NASA drew up a backup plan that calls tor launching a second shuttle if the first shuttle experiences problems. Here, Atlantis and the potential rescue shuttle, Endeavour, stand side-by-side on their launch pads.