Fog, rain delay shuttle's return to Earth

"There was a lot of cause for optimism, but at the end of the day, it was too low of a (cloud) ceiling," Mission Control told shuttle commander Alan Poindexter. "We know you worked it real hard," said Poindexter as the delay extended the shuttle's mission to 15 days. "We appreciate everything."

The shuttle will now aim to land at 7:33 am (1703 IST) on Tuesday at the Kennedy Space Center in Florida, but with rain and low clouds again in the forecast, NASA has also laid plans for a possible landing at Edwards Air Force Base in California at 1300 GMT.

Bryan Lunney, NASA's supervising flight director, said the shuttle and its seven member crew have enough provisions to remain in orbit until Wednesday if necessary. Although its return to Earth was postponed by rain, the US space agency said Discovery faces no threat from a huge ash cloud spewed by an erupting Icelandic volcano, which has shut down air traffic over Europe.

Discovery lifted off on April 5 and docked with the space station two days later, overcoming a communications antenna failure that crippled their rendezvous radar. During its two weeks in space, Discovery delivered nearly eight tons of scientific equipment and other supplies intended to fortify the orbiting science laboratory for operations beyond NASA's final shuttle launch.

The link-up united 13 US, Russian and Japanese astronauts from the two craft for 10 days. Four were women, the highest number of females in space at any one time. Over the course of three spacewalks, astronauts replaced a bulky external coolant tank. The ammonia reservoir circulates a coolant through outstretched radiators to disperse the heat generated by the station's internal electronics, including the life-support systems.

The science hardware delivered by Discovery included an Earth observation rack to hold cameras and spectral scanners for studies of the atmosphere, land forms, coastal areas as well as weather-induced crop damage.

Another new experiment will measure changes in muscle and joint health of astronauts during their long exposures to weightlessness, and a new freezer that Discovery delivered will hold blood and other specimens for experiments.

The mission is one of the last by the space shuttle programme and comes just days after US President Barack Obama laid out a new future for the space programme that made no mention of extending of the multi-billion dollar shuttle programme.