A famously mysterious military space plane operated by the US Air Force has launched from Florida, the third flight in a secretive test programme.
The reusable, unmanned craft is designed to operate in Earth orbit for extended periods. Its prior missions in 2010 and 2011 lasted 224 and 469 days.
The US government kept the timing of Tuesday's launch secret and has not said how long the mission will last.
That has prompted fevered speculation as to the craft's ultimate purpose.
NASA is gearing up for the Monday (Feb. 11) launch of an Earth-observation satellite that will continue a celebrated 40-year project to monitor our planet's surface from space.
The Landsat Data Continuity Mission is slated to blast off Monday at 1:02 p.m. EST (1802 GMT/10:02 a.m. PST) from Vandenberg Air Force Base in California. The LDCM satellite is the eighth overall in the Landsat program, which has been scrutinizing Earth from orbit continuously since Landsat 1 launched in 1972.