No, really, umbrellas in space:

The demand for high-speed, non-line-of-sight mobile communications - with the military tagging along behind the commercial market - has led to the "outing" of a fascinating set of technologies that were long confined to the world of black programs.
...
The challenge is to furl [a signal] antenna into the tight confines of a launch vehicle's payload fairing and have it open, with 100 per cent reliability, into exactly the right shape, and the video shows how it is done. These are large antennas - as the video notes, the most complex hoop-type structures are needed only when the antenna is more than 18 m (60 feet) in diameter. Harris' facilities can handle 30 m (100 foot) antennas.

I think it's always fun to hear about stuff nobody was ever supposed to hear about, even if it's decades after the fact.