Orbital Sciences' Glenn Weigle and Brett Gladish take the GN2 flow reading on NASA's Orbiting Carbon Observatory at Vandenberg Air Force Base.

With the fairing door off, Orbital Sciences' Glenn Weigle and Brett Gladish take the GN2 flow reading on NASA's Orbiting Carbon Observatory, or OCO, spacecraft on Launch Complex 576-E at Vandenberg Air Force Base in California. The encapsulated OCO tops Orbital Sciences' Taurus XL rocket, which is scheduled to launch Feb. 24. The spacecraft sits atop Orbital Sciences' Taurus XL rocket. At right is a portion of the umbilical tower attached to the upper stack. The spacecraft sits atop Orbital Sciences' Taurus XL rocket. At right is a portion of the umbilical tower attached to the upper stack. The spacecraft will collect precise global measurements of carbon dioxide (CO2) in the Earth's atmosphere. Scientists will analyze OCO data to improve our understanding of the natural processes and human activities that regulate the abundance and distribution of this important greenhouse gas. Photo courtesy of Jim Stowers, Orbital Sciences