After 25 years, the Hubble Space Telescope is still surprising us.
Against all odds, it’s 25 years and counting for the Hubble Space Telescope.
Few icons of science have had such a perilous existence, surviving political storms, physical calamities and the simple passage of time in the service of cosmic exploration.
In 1946, the astronomer Lyman Spitzer Jr. had a dream. A telescope in space, above the unruly atmosphere, would be able to see stars unaffected by the turbulence that blurs them and makes them twinkle. It would be able to see ultraviolet and infrared emissions that are blocked by the atmosphere and thus invisible to astronomers on the ground.
A look at Hubble
The Hubble Space Telescope is a joint project between NASA and the European Space Agency (ESA). Some basic facts:
Name: The telescope is named after U.S. astronomer Edwin Hubble, who, among other things, determined that the universe extended beyond the borders of Milky Way. He died in 1953.
Launch: It was launched on April 24,1990. It was deployed by the space shuttle Discovery on April 25,1990. It cost more than $2.5 billion to build. Its cumulative costs are estimated to be more than $10 billion.
NASA, ESA, Space Telescope Science Institute, Space.com
It took more than three decades for the rest of the astronomical community, the National Aeronautics and Space Administration (NASA) and Congress to buy into this dream, partly as a way to showcase the capabilities of the space shuttle, still in development then, and the ability of astronauts to work routinely in space.
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By the time the telescope was launched aboard the shuttle Discovery on April 24, 1990, it had been almost canceled at least twice and then delayed after the Challenger explosion in 1986.
When the Hubble was deployed, NASA’s spinmasters were instantly at the top of their game, hailing it as the greatest advance in astronomy since Galileo.
And it might have been except for one problem: The telescope couldn’t be focused. Instead, within days it became a laughingstock — a “technoturkey,” in the words of some critics.
Hubble, designed using spy-satellite technology, had an 8-foot mirror, just small enough to fit into the shuttle cargo bay.
But because of a measuring error during a testing process that was hurried to save money, that big mirror wound up misshapen, polished four-millionths of an inch too flat, leaving the telescope with blurry vision. It was the kind of mistake, known as a spherical aberration, that an amateur astronomer might make, to the disbelief and then the dismay of the engineers and contractors working for NASA.
For bright objects, astronomers could correct for the flaw with image-processing software. But for the fainter parts of the universe, the Hubble needed glasses.
NASA scientists shrugged off their heartbreak and figured out a way to provide corrective lenses.
Three years later, the space shuttle Endeavour and a repair crew led by Story Musgrave — astronaut, pilot, surgeon, spacewalker and Zen gardener — rode to the rescue.
Length: 43.5 feet
Weight: 24,500 pounds
Maximum diameter: 14 feet
Orbit: Average altitude of 353 miles, inclined 28.5 degrees to the equator.
Time to complete one orbit: 97 minutes.
Speed: 17,500 mph.
Hubble transmits about 120 gigabytes of science data every week. That would be roughly 3,600 feet of books on a shelf. The collection of pictures and data is stored on magneto-optical disks.
Astronomers using Hubble data have published more than 9,400 scientific papers, making it one of the most productive scientific instruments ever built.
Energy source: The sun
Mechanism: Two 25-foot solar panels
Batteries: 6 nickel-hydrogen (NiH), with a storage capacity equal to 20 car batteries.
NASA, ESA, Space Telescope Science Institute, Space.com
In five tense days of spacewalks, the crew replaced the telescope’s main camera and installed tiny mirrors designed to correct the Hubble’s vision.
The universe snapped into crystalline focus. And NASA could stop holding its breath.
The Hubble was the first big-deal telescope of the Internet age, and its cosmic postcards captivated the world. Trained on a patch of sky known as the Hubble Ultra Deep Field in 2010, the telescope’s eye discerned swarms of baby galaxies crawling out of the primordial darkness as early as only 600 million years after the Big Bang.
It also took one of the first visible-light photos of a distant planet, Fomalhaut b, orbiting its star.
In perhaps its most iconic image, “Pillars of Creation,” the Hubble recorded baby stars burning their way out of biblical-looking mountains of gas and dust in a stellar nursery known as the Eagle nebula.
These postcards were not without controversy regarding artistic license. The Hubble’s camera records in black and white, through filters that isolate the characteristic light from different atoms, such as sulfur, hydrogen and oxygen. Then the different layers are assigned whatever colors look good to the eye and best show off the underlying astrophysics, rather than their natural colors.
“Pillars of Creation,” for example, is presented in earth tones of green and brown and is oriented to look like a Turner landscape, while the natural emissions from the nebula are shades of red.
Technological hiccups have also continued. In 1999, four of the six gyroscopes that keep the telescope pointed failed, and the Hubble went into “safe mode.” A crew was hastily dispatched to replace the gyros. That was the first of what would be three trips to the telescope by John Grunsfeld, an astronaut, astronomer and now NASA’s associate administrator for science, who would win the sobriquet “Hubble Repairman” for his feats.
The telescope has been reborn again and again over the years, thanks to the efforts of astronaut servicing crews. Astronauts wearing the equivalent of boxing gloves have gradually learned how to do things the telescope’s designers had never dared dream of, fiddling with its innards, replacing circuit boards and performing the equivalent of eye surgery and computer repairs in space.
Hubble was hitting its stride, getting better and better, when the Columbia space shuttle disintegrated in 2003, killing all seven astronauts on board. That presaged the end of NASA’s space-shuttle program.
The agency’s administrator, Sean O’Keefe, canceled what was to be the final Hubble servicing mission on the grounds that it was too risky. Without it, the telescope would be doomed to die in orbit within two or three years when its batteries and gyros failed again.
The decision was announced and defended by Grunsfeld, who was then NASA’s chief scientist. “Being an astronaut, there are not a lot of things that have really shocked me in my life,” Grunsfeld recalled later. “But I don’t think anybody could ever prepare themselves for, you know, trying to bury something that they have said, ‘Hey, this is worth risking my life for.’ ”
O’Keefe’s decision ignited a national outcry. Schoolchildren offered to send their pennies to NASA to help pay for the telescope.
Behind the scenes, however, Grunsfeld and other astronomers and NASA engineers were working on ways to save Hubble, perhaps by sending robots to work on it.
The robotic approach was eventually rejected by a National Academy of Sciences panel, but it had served as a placeholder to keep the teams of engineers together. In the end, O’Keefe resigned, and his successor, Michael Griffin, reinstated a servicing mission.
In 2009, Grunsfeld led one last mission to the Hubble. He was the last human to touch the telescope, patting it as the shuttle Atlantis prepared to let it go again. But that does not mean the telescope has ceased to touch humanity. On the contrary, it continues to deliver news about this thing we are all part of — a universe — but barely understand.
This spring, astronomers announced that the Hubble had seen a sort of cosmic mirage known as an Einstein ring, in which they could view multiple reruns of a star that died in a stupendous supernova explosion more than 9 billion years ago on the other side of the cosmos.
NASA is making a big deal of the Hubble anniversary, with a weeklong symposium in Baltimore, where the Space Telescope Science Institute is based.
“This is a celebration partly about the telescope and partly about NASA,” Grunsfeld said, “but much of it is a celebration of people doing science.”
The Hubble today is more powerful than its designers ever dreamed, and it has a good chance of living long enough to share the universe with its designated successor, the James Webb Space Telescope, due to be launched in 2018. The Hubble’s longevity is something few would have imagined 10 years ago, yet NASA is planning a 30th-anniversary celebration in 2020, Grunsfeld said.
After a quarter-century, the telescope’s future and promise are still as big as the sky and our ignorance of what lies behind it.