Re: "from the GPS system work out the wind speed on the surface." How?
From the Wikipedia article, they are using " bi-static scatterometry". "Bi-static" merely means the transmitter and receiver are not co-located. "scatterometry" is the extraction of information from the ways in which a radio wave is modified by a surface that reflects it. Use of the GPS satellite as the transmitter is clever: the receiving satellite uses the GPS system itself to learn the position of the transmitter and of itself with extreme precision. However, the GPS signal is quite weak even before it hits the surface and is reflected, so I'm sure they must integrate over a long time. The GPS signal is intended to be used for exactly this type of signal integration (i.e., spread spectrum), but the reflected signal has got to be at least another 30 dB down in the dirt, so this is pretty impressive.
"Scatterometry" is apparently a well-developed discipline. I assume they get loads of calibration against physical surface measurements, probably pretty much continuously, as they measure the conditions near monitoring buoys.
Pegasus is pretty much ideal for this very specific satellite's size/weight/orbit parameters, probably because the design team chose to stay within Pegasus' parameters. Expensive in terms of $/lb-to-orbit, but very inexpensive on a $/launch basis, so they can launch more to extend coverage or extend mission life.