A water flow problem on Tuesday forced the US space agency to postpone the launch of a satellite to track atmospheric carbon dioxide, a leading greenhouse gas.
The Orbiting Carbon Observatory-2 was due to take off atop a Delta 2 rocket at 2:56 am Pacific time (0956 GMT) from Vandenberg Air Force Base in California. But the operation was halted 46 seconds before scheduled liftoff time due to an issue with water flow to the rocket, NASA said.
The launch window on Tuesday was quite short, just 30 seconds.
The timing had to be precise so that the satellite could join the A-Train, a constellation of five other international Earth-observing satellites.
More details on the nature of the problem and a time for the next launch attempt were expected later Tuesday, NASA commentator George Diller said.
The Orbiting Carbon Observatory-2 is a replacement for a similar satellite that was lost during a launch malfunction in 2009.