[dedward]

"NanoSail-D will remain closer to home. "Our mission is to circle Earth and investigate the possibility of using solar sails as a tool to de-orbit old satellites and space junk," explains Alhorn. "As the sail orbits our planet, it skims the top of our atmosphere and experiences aerodynamic drag. Eventually, this brings it down.""

Pretty clearly not a solar sail...

[51Cards]

"They'd also like to measure the pressure of sunlight on the sail, although atmospheric drag could overwhelm that effect."

Dual purpose study.