CAPE CANAVERAL, Fla. -- Space shuttle Endeavour's astronauts squeezed in one last day of Earth mapping on Sunday, giving scientists more radar data than they had expected a week ago.
By the time the astronauts pull in their 197-foot radar mast Monday morning, they will have surveyed three-quarters of the world's terrain.
That equates to 43.5 million square miles mapped at least twice. Double imaging is needed to create ultraprecise 3-D maps of the planet's peaks and valleys, as far north as Alaska and as far south as the tip of South America.
NASA and its partner, the National Imagery and Mapping Agency, expect the maps to be the most complete and accurate ever produced.
The Defense Department will use the maps to improve its aim of missiles and its deployment of troops. Most everyone else will have to settle for less precise data because of national security issues, but the information still will be far superior to what is currently available.
"There's every reason to be excited," said the mapping agency's Thomas Hennig.
The astronauts would have mapped 2.5 million square miles more if a thruster hadn't malfunctioned on the end of the mast, the longest rigid structure ever flown in space. A weeklong effort to conserve fuel aboard Endeavour allowed the astronauts to continue mapping on Sunday and bought additional nine hours and 10 minutes.
Those extra 10 minutes, approved over the weekend, will allow the astronauts to survey Australia one last time before shutting down their radar over the South Pacific.
Every drop of shuttle fuel has been used or appropriated, if not for mapping then for Tuesday's scheduled return to Earth and possible landing delays.
To extend mapping into Monday, NASA gave up the possibility of sending two astronauts on an emergency spacewalk to crank in the mast if it jams. That means the mast will have to be dumped overboard if it does not retract.
Michael Kobrick, a scientist working at Mission Control, said the mast extended from Endeavour's cargo bay with ease on Feb. 11. Except for the problem with the thruster, the radar system has worked flawlessly since it began working Feb. 12.
Engineers put a tiny thruster on the end of the mast to hold it steady for mapping. But the nitrogen-gas line feeding the thruster had a leak or a clog, making the thruster virtually useless.
To compensate for the lack of thrust, Endeavour's jets had to be fired more frequently and, as a result, used up more fuel than planned. Flight controllers found ways to conserve the shuttle's fuel and managed to save all but 13 hours of mapping.
As it is, the astronauts will bring back enough radar data to fill 20,600 compact discs. It will take scientists one to two years to go through it all.