NASA said the countdown stopped at 46 seconds because of the failure of the launch pad water suppression system and added that the launch team has completed troubleshooting the snag.
A valve that is part of the pulse suppression water system had failed to function properly during the final minutes of the launch yesterday, the space agency said.
"The failed valve has been replaced with a spare, and the system is being tested in preparation for Wednesday's launch attempt," it said.
"The observatory will study how these sources and sinks are distributed around the globe and how they change over time," NASA said.