Tuesday, March 03, 2009

Trivia! Good Stuff about the HST

I was reading an absolutely fascinating op-ed piece about what was once called the biggest waste of money NASA had ever omitted. TechRepublic's Jay Garmon was writing about the Hubble Space Telescope and some really good back story. As we are all aware, the Hubble was launched with a significant flaw in it's primary mirror. This error crippled Hubble to near uselessness. Lots of bad words were thrown around but for the most part the fault has to fall at the feet of the manufacturer of the mirror assembly, Perkin-Elmer. The original mirror was checked for accuracy by a device called a null corrector. The problem was that Perkin-Elmer's corrector was faulty. To compound the problem, they used another null corrector to check the mirror at the end of production and THAT device caught the error. Perkin-Elmer chose however to believe the defective corrector's readings and therefor pass the ill fated mirror. You want to know how big the error was that crippled a multi-million dollar telescope? 2.3 microns. 1/3 the width of a human blood cell or 1/50th the width of a human hair. Unbelievable huh? Did you know that there were in fact 3 mirrors ground for NASA? Yep, the last 2 were perfectly ground....imagine!
Obviously they would not ever be used on the Hubble so they were "recycled". One is on display at the Smithsonian National Air and Space Museum and since these mirrors are among the finest ground mirrors in existence, as Jay puts points out, it would be a shame not to build a telescope around it. From the article:
  • The second backup to the Hubble’s primary mirror is now the central optic of the 2.4 meter SINGLE Telescope at the Magdalena Ridge Observatory in New Mexico.
  • The SINGLE went online Sept. 1, 2008 and is currently under contract with NASA to track Low Earth Orbit (LEO) objects and to support the operations and observations of the Fermi Gamma-ray Space Telescope.
Of course what makes all this ironic is why NASA had 3 mirrors made - you ready? NASA wanted to guard against a problem in the manufacturing process.

Want more irony? Kodak and Itek put in a bid to make the mirror. They would each build one and then check each other's work. Perkin-Elmer was touting a computer controlled manufacturing process that was guaranteed to produce highly accurate mirrors. But NASA required Perkin to sub contract for conventionally ground backup mirror. Guess who they sub contracted with....oh yeah...Kodak / Itek. The final irony is that the sub contracted mirrors were perfect and it was the flawed computer controlled ground mirror that flew.

And that is why I like trivia!

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