What is the Pentagon’s secret space drone doing?

http://nypost.com/2014/09/28/what-is-the-pentagons-secret-space-drone-doing/

For almost two years, an unmanned space plane bearing a remarkable resemblance to NASA’s space shuttle has circled the Earth, performing a top-secret mission. It’s called the X-37B Orbital Test Vehicle — but that’s pretty much all we know for certain.