A security guard waits to clear NASA's Operational Environmental Satellite System Preparatory Project NPP satellite.

A security guard waits to clear NASA's National Polar-orbiting Operational Environmental Satellite System Preparatory Project (NPP) satellite through the gates of Vandenberg Air Force Base in California.

NPP represents a critical first step in building the next-generation of Earth-observing satellites. NPP will carry the first of the new sensors developed for this satellite fleet, now known as the Joint Polar Satellite System (JPSS), to be launched in 2016. NPP is the bridge between NASA's Earth Observing System (EOS) satellites and the forthcoming series of JPSS satellites. The mission will test key technologies and instruments for the JPSS missions. NPP is targeted to launch Oct. 25 from Space Launch Complex-2 aboard a United Launch Alliance Delta II rocket. For more information, visit http://www.nasa.gov/NPP.

Photo credit: NASA/Dave Uveges, VAFB