Shuttle group (4)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">shuttle group</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for nasa that I've seen before include "rocket launcher" , "US agency responsible for space flight" , "US headquarters for space exploration" .)