Looks like the infamous Space Core from Portal 2

The Portal 2 blog has a picture of the panel, which was evidently sent in by an anonymous NASA technician. It will be aboard a resupply craft that launches on Friday at 10.06 EST.

"In spaaaaaaace!"

"When we mentioned an 'anonymous tech at NASA' we weren't kidding: NASA in no way officially endorses secretly laser-engraving characters from Portal onto their spacecraft," clarified the Valve blog. Now, let's all enjoy some classic space-babble (if you've finished Portal 2, that is - otherwise, be wary of spoilers):