CAPE CANAVERAL, US - Space Exploration Technologies will try again Tuesday to launch a Falcon 9 rocket with a US satellite intended to watch for threatening solar storms, NASA said on Monday.
Liftoff from Cape Canaveral Air Force Station in Florida had been planned for Sunday, but was called off two minutes before launch because of a problem with an Air Force radar system needed to track the rocket during flight.
The launch was then postponed to Monday, but a poor weather forecast prompted SpaceX, as the California company is known, to reschedule for Tuesday.
Liftoff with the Deep Space Climate Observatory, or DSCOVR, a partnership of NASA and the National Oceanic and Atmospheric Administration, is now planned for 6:05 p.m. EST (2305 GMT).
The delay positions SpaceX, a rapidly growing firm owned and operated by technology entrepreneur Elon Musk, for an unprecedented simultaneous rocket launch and spaceship recovery, as it prepares also for Tuesday's return of a Dragon cargo ship from the International Space Station.
"Tuesday will be a busy day, but SpaceX has planned and prepared for this scenario. We have separate operations and recovery teams on both coasts so we are equipped to handle both events simultaneously," said SpaceX spokesman John Taylor.
The Dragon capsule, launched during the last Falcon 9 rocket flight in January, is due to depart the station at 2:09 p.m. EST (1909 GMT).
The International Space Station, owned and operated by 15 countries, is a US$100 billion(S$135 billion) laboratory that flies about 260 miles (418 km) above Earth.
Shortly after Dragon's departure, a SpaceX launch team in Florida will decide whether to proceed with fueling the two-stage rocket with kerosene and liquid oxygen for flight.
Meteorologists on Monday were predicting a 70 per cent chance of acceptable weather for the sunset launch, NASA said.
As the launch countdown is under way, the Dragon capsule will fire its braking rocket to leave orbit, aiming for a parachute splashdown in the Pacific Ocean, about 310 miles (500 km) off the coast of Baja California, at 4:44 PST (0744 EST, 0044 GMT).
Meanwhile in the Atlantic, a second SpaceX recovery team will be stationed near a floating landing pad where the discarded first stage of the Falcon rocket, due to launch at sunset, will attempt to touch down.
SpaceX has been working on technology to recover and reuse its rockets, potentially slashing launch costs.
The primary goal of Tuesday's launch is to send the DSCOVR observatory, a US$340 million(S$460 million) project, into an orbit that is more than three times farther from Earth than the moon.
Once in position, the spacecraft will serve as a weather buoy to give forecasters about an hour's advance notice of potentially dangerous solar storms, which can damage satellites, interrupt GPS signals and disrupt power grids on Earth.
DSCOVR also has two Earth-watching sensors, including a camera that will take pictures every two hours of the sun-lit side of the planet that will be posted on the Internet.