The Hubble Space Telescope has survived 20 years in space ? including unprecedented surgical repairs to its mechanical eyes, heart and brain ? to become one of the most beloved astronomical icons in history.
But it wasn't always the crown jewel of space-based astronomy. In fact, just after it reached orbit on April 24, 1990, the Hubble Space Telescope was on the verge of becoming a national embarrassment. It had a flawed mirror and took fuzzy pictures that were a far cry from the crisp views deep into the universe that astronomers expected.
Ed Weiler, NASA's associate administrator for science, was there at the beginning. It was he who ? as Hubble's program scientist at the time ? broke the news the press and the world that Hubble's main mirror had a major defect ? a spherical aberration caused by a manufacturing error. It would take three years before NASA was ready to mount a repair mission in 1993, but Weiler was also there on Dec. 18 of that year when the first new images from Hubble reached Earth.
Those photos were crystal clear.
"It was just vindication," Weiler told SPACE.com, adding that it was most cathartic moment in his life since the birth of his two children. "We realized immediately that we had nailed the prescription."
Hubble surgery in space
What NASA and a crew of space shuttle astronauts had done was effectively perform eye surgery on Hubble ? a 12 1/2 ton space telescope that flies more than 350 miles (563 km) above Earth. The mission was a desperate bid to salvage a space telescope built by NASA and the European Space Agency which has since swelled into a two-decade, $10 billion-mission to explore the universe.
Two new cameras, including the Wide-Field Planetary Camera 2 (WFPC-2) ? which took many of Hubble's most famous photos ? were installed during the fix. You can see them today at the Smithsonian Air & Space Museum in Washington, D.C., a short walk from Weiler's office at NASA headquarters.
"I call it the camera that saved Hubble," Weiler said of the WFPC-2. "I really give it credit for putting Hubble on the world map, so to speak. And now being able to go up to it and almost touch it ? is really quite incredible. "
The new cameras corrected Hubble's vision completely by counteracting the spherical aberration mirror defect afflicting the space telescope.
"Spherical aberration happens when the primary mirror is polished incorrectly," John Trauger, WFPC-2 principal investigator at NASA's Jet Propulsion Laboratory in Pasadena, Calif., explained last year just before the last Hubble flight. "You can think of the mirror as a very shallow bowl. With spherical aberration it's just a little too shallow, a little too flat."
Faulty test equipment used during the manufacture of Hubble's 8-foot (2.4-meter) mirror was later blamed as the cause. All of the later instruments installed on Hubble during subsequent servicing flights were built to automatically take the mirror flaw into account while observing the universe.
Legacy in the stars
The 1993 repair mission saved Hubble from going down in history books as a colossal cosmic flop. The drama surrounding the telescope's triumph over blurry vision ? as well as the stunning photos that followed ? have endeared it to scientists and the public ever since.
Hubble has uncovered countless mysteries of the cosmos, including supermassive black holes, dark matter and dark energy, the existence of planetary systems beyond our own.
The orbital observatory has also helped rewrite astronomy textbooks and shown that stars formed much sooner after the universe began than previously thought, and that the process that forms planets like Earth and its solar system are relatively common. Weiler, for one, is thrilled.
"I always like things that show we humans don't know everything we think we know," he said.
Hubble has also peered back to just 600,000 years after the birth of the universe, which is 13.7 billion years old. Still, its longevity has surprised even its creators.
"If you would have told me in 1990 that Hubble was going to do everything we promised ? that we'd go way beyond those capabilities, and go beyond 15 years to get to 20 years, and probably have 25 or 30 to look forward to, I would have told you we were on the wrong medication," Weiler said.
Weiler has added his own take to the Hubble story in the new book "Hubble: A Journey Through Space And Time," which was released this month on the heels of a new IMAX film ? "Hubble 3-D" ? which chronicles the space telescope's legacy and final overhaul.
Made for space repairs
Hubble was the first of NASA's Great Observatories in space. It was named after renowned astronomer Edwin Hubble.
But unlike the space observatories that followed, only Hubble alone was built to be visited by astronauts again and again. In all, astronauts flew five Hubble servicing missions ? most recently in May 2009 ? to swap out old, worn out parts and install new state-of-the-art instruments.
"I had Hubble in my hands, literally. We all did and that's a tremendous responsibility," former astronaut John Grunsfeld, who flew to Hubble three times (including the last flight), told SPACE.com in a recent interview. "Rule number one was 'Don't Break Hubble.'"
After the first servicing mission in 1993, astronauts returned to Hubble in 1997, 1999, 2002 and 2009. They performed brain surgery to replace old main computer parts, and mechanical heart surgery to upgrade Hubble's power and solar array battery systems.
NASA initially cancelled the final servicing mission to Hubble after finding it too risky following the tragic loss of shuttle Columbia and seven astronauts in 2003. After toying with the idea of sending a robot to fix Hubble, NASA decided to send one last crew instead on the STS-125 mission, which included Grunsfeld. ?
Not your grandfather's telescope
During the last mission to Hubble, Grunsfeld and his crewmates fixed broken cameras that were never built to be repaired in space. The astronauts removed hundreds of tiny screws, ripped a handhold bar off to get to one broken instrument and performed five grueling back-to-back spacewalks knowing that if something went horribly wrong, they'd have to wait until a second space shuttle could be launched on a rescue flight.
Despite those daunting odds, the Hubble repair marathon was a complete success. In the late summer of 2009, the first new photos from Hubble revealed spectacular new views of the universe.
With the final upgrades, Hubble is just about a completely new space telescope. Its new instruments should make it 90 times more powerful than when it launched, NASA officials have said.
"This isn't your grandfather's telescope like it was in 1990," Weiler said.
Since leaving Hubble for the last time, Grunsfeld has since retired from spaceflight. He left NASA's astronaut corps to join Hubble's science team at the Space Telescope Science Institute in Baltimore, Md., where he serves as deputy director.
It's Hubble every day, not a bad trade, he has said.
"The observations that Hubble makes, and the ability of astronomers and the scientists to figure out how the universe works from these observations is even more amazing than anyone has ever imagined," Grunsfeld said.
NASA is now working on its next great space observatory ? the infrared James Webb Space Telescope ? slated for launch in 2014. Weiler and other astronomers hope Hubble will still be going strong by then in order to work in tandem with the new space telescope. ??
But for now, Weiler said he plans to spend Hubble's 20th birthday at home, most likely cutting his grass and dreaming of the distant parts of the universe the telescope has seen. And, of course, he will think of the American people who made the space telescope possible, then funded efforts to focus its vision and keep the cosmic window on the universe wide open.
"It was the American taxpayers that made Hubble possible," Weiler said. "And I thank them for all that they could do."
- Images - 20 Years of the Hubble Space Telescope, Part 2
- Top 10 Most Amazing Hubble Discoveries
- Why Are Space Telescopes Better Than Earth-Based Telescopes?