The first mirror segment of the James Webb Space Telescope, the all-purpose instrument that will take the mantle of "most awesome" telescope from Hubble in 2014, is polished.

There are 18 mirror segments to go, but it still marked a milestone on the telescope's march towards flight-readiness.

The huge mirrors require incredible precision for collecting the tiny amounts of photons arriving at Earth from distant objects. Even the tiniest mistakes can kill the performance of a telescope.

Recall that an erroneously polished mirror fouled up Hubble's launch. The telescope got into orbit before researchers realized that things weren't working quite right.

It took a separate Shuttle mission – STS-61 – to get the telescope working properly.

Clearly, NASA doesn't want a repeat of that experience, so the agency and its contractors are taking special care polishing up its latest space observatory. This time around, everyone is taking their own measurements.

"For validation purposes, we’re planning four sets of completely different cross checks and verification tests to authenticate the outcome of the mirror cryotests," said Scott Texter, Northrop Grumman Webb Optical Telescope Element Manager. "If any discrepancies surface, we can then investigate and re-verify."

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