PARIS -- A radar boom antenna aboard Europe's Mars Express satellite that had failed to lock into place was successfully deployed May 10-11 after ground controllers maneuvered the satellite to expose the boom to the sun, according to the European Space Agency (ESA) and European scientists.

The successful operation makes it more likely that ESA will authorize deployment of the second 20-meter-long boom in the coming weeks following an investigation into the first boom's problem.

The non-deployment of the antenna had so worried European science managers that they declined to authorize a two-year extension of the Mars Express mission during a May 9-10 meeting of Europe's Science Program Committee (SPC).

Risto Pellinen, chairman of the SPC, said May 12 that the SPC probably would have authorized the two-year extension, to December 2007, if the balky radar antenna had been successfully deployed before the SPC meeting in Helsinki, Finland. The two-year extension has been budgeted at 15.6 million euros ($20.3 million).

Pellinen said the SPC is scheduled to meet next in September and is all but certain to agree to the Mars Express mission extension -- assuming the second radar boom is successfully deployed by then. The SPC had feared that Mars Express' other instruments might be unable to function fully because of the disequilibrium caused by flying with a single, partially deployed 20-meter antenna, Pellinen said.

Working with NASA's Jet Propulsion Laboratory, which supplied the radar antenna, Mars Express program managers concluded that the longer-than-expected storage of the boom might account for the fact that one of its 13 joints, or hinges, failed to lock into place during the May 8 deployment.

ESA said in a May 11 statement that the Kevlar and fiberglass boom material might have been affected by the prolonged storage at cold temperatures.

Mars Express reached Mars orbit in December 2003. Its radar antennas were not immediately deployed because of concerns that there might be of a whiplash effect created by unfurling the two 20-meter antennas. That concern did not surface until after the satellite had been launched and once it reached Mars ESA officials wanted to give the satellite's other instruments time to operate before running the risk of damaging them during the radar deployment.

Moving the satellite to fully expose its non-deployed element to the sun apparently worked by heating the affected joint and allowing it to lock into place. The radar antennas are designed to search for water up to a depth of several kilometers beneath the surface of mars.