Diagram from the Allen report.
It was a misalignment of about 1.3mm. "Holy Christ," says Pellerin. "In an optical system this is like missing by a thousand miles."
The review board had considered three possibilities when it came to the null corrector, according to the Allen report:
"(1) The field lens was inserted backward.
"(2) The index of refraction of the field lens was incorrect (i.e., the wrong glass was used).
"(3) The optical elements were incorrectly spaced (a circumstance that seemed highly unlikely because of the method used to set the lens spacings)."
After an analysis of the null corrector, which had been stored by the contractor after the mirror was finished, number three turned out to be the culprit,"
"So the next thing that happened was really kind of interesting," Pellerin says.
"Being a technically trained person and completely unaware of the power of social constructs, I thought 'Great it's a technical failure.' I mean it's not my fault, I wasn't even there. I'm off the hook — that's what I'm thinking. Because these things are usually unpleasant when you're responsible for them."
But the chair of the failure review board wanted to look into it further. What he found was that when the mirror was removed from the bed of nails and put in its three point mount, it was tested again. "We tested that mirror over and over and over with a different kind of device, the old style refractive null corrector," Pellerin says.
The results? "Half wave of error, half wave of error, half wave of error."
"So some people sat down and said, 'What's going on?" Pellerin recalls. "The mindset was that the mirror can not be other than perfect. So something else is happening. They concluded that the mirror was sagging under the force of gravity in the three point mount rather than being on the bed of nails by half a wave.
"Well it turned out that was wrong. But they rationalised, rationalised, rationalised. What kind of minds does a project like Hubble attract? The best. So [Allen] said, 'I want to understand why the smart guys working on it didn't go dig in and find out what's going on.'"
The project had suffered other challenges beyond fabricating and mounting the mirror; staff were being "hammered" all the time, Pellerin says. In addition there was constant angst about how far the project had gone over budget. "Hubble's initial budget was $434 million we closed it at $1.8 billion just for the flight segment; big overruns."
"So the way it works is you tend to blame the people doing the work," Pellerin says. "So we're hammering on them, hammering on them so they had no free time or no inclination to track down anything that wasn't a critical problem because we have other critical problems. Difficult technical things that we couldn't solve yet."
The review board also found that a hostile environment had been created for the contactor, which meant "they told us about any problem at their peril," Pellerin says.
When the board's findings were reported to Congress, it was found that the question of leadership had been at the centre of the project's failure. "Now you might have thought that would have heaped criticism on me, but everybody else around me is technical too. The whole NASA management chain is technical people. They all did just like I did with Challenger: They heard that but it didn't register, didn't register on me."
In the wake of the Hubble disaster, Pellerin found himself in the office of the congresswoman who headed NASA appropriations. She wasn't happy. "When she got through throwing newspapers, she's screaming at me and there's spittle collecting on my glasses. We just stood there and she puts her finger in my chest and says this is done. We're going to forget this ever happened. You've humiliated me with this, you've made me look like an idiot with what you've done. And so there will not be any servicing for [Hubble]. Ever."