A Long and Bumpy Road
In 1946, Yale astronomy professor Lyman Spitzer wrote a paper detailing the advantages of an Earth-orbiting telescope for deep observations of the universe.4 The concept had been floated even earlier, in 1923, by Hermann Oberth, one of the pioneers of modern rocketry. In 1962, the U. S. National Academy of Sciences gave its imprimatur to the idea, and a few years later Spitzer was appointed chair of a committee to flesh out the scientific motivation for a space observatory. The young space agency NASA was to provide the launch vehicle and support for the mission. NASA cut its teeth with the Orbiting Astronomical Observatory missions from 1966 to 1972.5 They demonstrated the great potential of space astronomy, but also the risks—two of the four missions failed. We’ve already encountered Spitzer since he gave his name to NASA’s infrared Great Observatory. Spitzer worked diligently to convince his colleagues around the country of the benefits of such a risky and expensive undertaking as an orbiting telescope.
After the National Academy of Sciences reiterated its support of a 3-meter telescope in space in 1969, NASA started design studies. But the estimated costs were $400-500 million and Congress balked, denying funding in 1975. Astronomers regrouped, NASA enlisted the European Space Agency as a partner, and the telescope shrunk to 2.4 meters. With these changes, and a price tag of $200 million, Congress approved funding in 1977 and the launch was set for 1983. More delays followed. Making the primary mirror was very challenging and the entire optical assembly wasn’t put together until 1984, by which time launch had been pushed back to 1986. The whole project was thrown into limbo by the tragic loss of the Challenger Space Shuttle in January 1986. When the shuttle flights finally resumed, there was a logjam of missions so another couple of years slipped by.6
Hubble was launched on April 24, 1990, by the shuttle Discovery. A few weeks after the systems went live and were checked out, euphoria turned to dismay as scientists examined the first images and saw they were slightly blurred. The telescope could still do science but some of the original goals were compromised. Instead of being focused into a sharp point, some of the light was smeared into a large and ugly halo. This symptom indicated spherical aberration, and further in-flight tests confirmed that the primary mirror had an incorrect shape. It was too flat near the edges by a tiny amount, about one-fiftieth of the width of a human hair. Such was the intended precision of Hubble’s optics that this tiny flaw made for poor images.7 Hubble’s mirror was still the most precise mirror ever made, but it was precisely wrong.
The spherical aberration problem may be ancient history and in the rearview mirror now, but at the time it was a public relations nightmare for NASA. Its flagship mission could only take blurry images. Commentators and talk show hosts lampooned the telescope and David Letterman presented a Top Ten list of “excuses” for the problem on the Late Show with David Letterman.8 More seriously, the episode became fodder for case studies in business schools around the country. The fundamental error was the result of poor management, not poor engineering. The Space Telescope project had two primary contractors: Perkin-Elmer, who built the optical telescope assembly, and Lockheed, who built the support systems for the telescope. There was also a network of two dozen secondary contractors from the aerospace industry. The mission was jointly executed by Marshall Space Flight Center and Goddard Space Flight Center, whose relationship involved rivalry and was not always harmonious, with overall supervision from NASA Headquarters. Complexity of this degree can be a recipe for disaster without tight and transparent management, and clear communication among the best technical experts.
When the primary mirror was being ground and polished in the lab by Perkin-Elmer, they used a small optical device to test the shape of the mirror. Because two of the elements in this device were mis-positioned by 1.3 millimeters, the mirror was made with the wrong shape. This mistake was then compounded. Two additional tests carried out by Perkin-Elmer gave an indication of the problem, but those results were discounted as being flawed! No completely independent test of the primary mirror was required by NASA, and the entire assembled telescope was not tested before launch, because the project was under budget pressure. Also, NASA managers didn’t have their best optical scientists and engineers looking at the test results as they were collected. The agency was embarrassed and humbled by the failure. Their official investigation put it succinctly: “Reliance on a single test method was a process which was clearly vulnerable to simple error.”9 In this way a multi-billion-dollar mission was hamstrung by a millimeter-level mistake and the failure to do some relatively cheap tests. In the old English idiom: penny wise, pound foolish. The propagation of a small problem into a huge one recalls another aphorism from England, where a lost horseshoe stops the transmission of a message and the result affects a critical battle: for the want of a nail, the war was lost.