WASHINGTON: NASA was set to blast off probes yesterday on a landmark lunar exploration mission to scout water sources and landing sites in anticipation of leading man back to the moon.

The US space agency, hoping to send astronauts to Earth's natural satellite by 2020 for the first visit since 1972, announced it is on course to launch the dual LRO and LCROSS missions atop an Atlas V rocket from Florida's Kennedy Space Center.

A day after scrubbing the shuttle Endeavour launch for the second time in a week because of a nagging hydrogen fuel leak, NASA said it has three launch windows over 20 minutes starting from 5:12 pm (2112 GMT; 5:12 am Beijing time). If none work out, officials have inked in three more opportunities for today.