Remember when the Hubble Space Telescope was more punchline than science powerhouse?
30 years ago astronauts embarked on ambitious mission to fix Hubble ... and NASA's reputation
Today is the thirtieth anniversary since NASA launched the first servicing mission for the stricken Hubble observatory, a record that lands just as the the space telescope faces a fresh round of fixes.
On December 4, 1993, at 0926 UTC, the Hubble Space Telescope (HST) was secured in the payload bay of Space Shuttle Endeavour, ready to be serviced in a mission on which the future of NASA depended.
After decades of stunning imagery and science, it is difficult to imagine the HST being the punchline of a bad joke... a very, very expensive bad joke. However, 30 years ago, the HST was in fact a disappointment. A flaw in its main mirror had reduced the space telescope's capabilities, and since its launch in April 1990 aboard the Space Shuttle Discovery, the flagship observatory had returned images that were not as sharp as scientists – or the media – had been promised.
This meant that NASA's reputation was on the line as the hugely ambitious mission to service the HST and correct its optics got underway. After all, how could the agency be trusted with billions of taxpayer dollars to build its new space station if this was its idea of quality control?
Perhaps this view was harsh, yet there was a real danger that the HST might have to be abandoned or scientists accept the degraded capability if the servicing mission did not go to plan.
NASA's mission history includes a quote from John Bahcall, an astrophysicist who had advocated for the telescope. Bahcall told the New York Times in 1993: "If the Hubble repair is a failure, we can write off space science for the foreseeable future."
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The crew consisted of veteran astronauts, including one from the European Space Agency (ESA). Five spacewalks were required, with alternating astronauts. As well as the corrective optics – dubbed COSTAR for Corrective Optics Space Telescope Axial Replacement – the Shuttle also carried the Wide Field and Planetary Camera 2 (WFPC2), some replacement gyroscopes, upgrades for the HST's flight computer, and new solar arrays.
The latter was the result of a discovery that the existing solar arrays would expand and contract excessively as the telescope orbited, causing yet another headache for scientists in the form of a jitter. And the gyros? Three of the six onboard had already broken down. It was decided that four would be replaced to restore full redundancy.
The gyros were replaced in the first spacewalk, the solar arrays in the second, the WFPC in the third – the WFPC2 included its own optical correction system, and COSTAR went in on the fourth alongside the computer upgrades. For COSTAR, the High Speed Photometer had to be sacrificed; while it had proven helpful in identifying the problem with the HST's main mirror, its mission had been compromised by the optical issues.
Things were tidied up on the fifth spacewalk, including replacing the HST's solar array drive electronics.
On the ninth day of the mission – December 9, 1993 – the HST was released. The Shuttle made a successful landing a few days later.
Looking back 30 years, it isn't easy to appreciate the scale of the mission's success. Just over a week later, on December 18, 1993, astronomers gathered at the Space Telescope Science Institute in Baltimore to view the first new image from the telescope – a star, free of the blurring from the HST's flawed primary mirror.
According to the NASA Hubble Mission Team: "The new images were so dramatically different that even though the telescope needed around 13 weeks for adjustment to reach its full capabilities, NASA released them early."
"It's fixed beyond our wildest expectations," said Ed Weiler, Hubble chief scientist during SM1 [Servicing Mission 1], at a January 1994 press conference.
The HST would receive four subsequent servicing missions between 1997 and 2009, updating its instruments and replacing hardware.
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For NASA, the mission demonstrated the agency's and its engineers' competency. The experience gained also fed into future programs.
"A lot of the knowledge that was developed there transferred directly to construction of the International Space Station and it'll transfer to the things we do with [the future orbiting lunar space station] Gateway someday," said Kenneth Bowersox, associate administrator for NASA's Space Operations Mission Directorate, who was also an astronaut on Servicing Mission 1.
The first Hubble servicing mission showed that NASA was still as adept at snatching victory from the jaws of defeat – other missions such as the Skylab recovery and Apollo 13 spring to mind – even as it reeled from its unwanted status as punchline to a dozen terrible jokes.
The latest challenge facing Hubble came last month when the telescope went into safe mode on three separate occasions following ongoing issues with the gyroscope, which is clearly in need of a fix. NASA is running tests ®