Mission operators put out a call to the Comet Nucleus Tour spacecraft - the first of two scheduled attempts to contact the NASA satellite this week - but CONTOUR remains silent.

Yesterday morning the team began sending commands toward the spacecraft's expected location through NASA's Deep Space Network (DSN), looking to trigger a transmission from CONTOUR's communications system. Operators at the Johns Hopkins University Applied Physics Laboratory (APL) employed the largest DSN antennas - 34 and 70 meters across - supplemented by sophisticated radio-science equipment able to pick up low-frequency signals. Split into shifts, the 12-hour send-and-listen session ended at 12:10 a.m. EST today with no signal from the spacecraft.

The team will try one more time to reach CONTOUR on Dec. 20, during a 4-hour session starting at 8 a.m. EST. CONTOUR Project Manager Edward Reynolds, of APL, says the chances of obtaining a signal remain remote. "If we don't get a signal on Friday, our recommendation to NASA will be that we not try again," he says.

CONTOUR hasn't been heard from since firing its solid rocket motor on Aug. 15, during a maneuver to boost the spacecraft from a parking orbit around Earth. Ground-telescope pictures taken shortly after the rocket burn indicated CONTOUR had broken up into at least three pieces. The team is focusing on the largest section - thought to be the bulk of the spacecraft - 42.5 million miles from Earth and speeding away at more than 23,000 miles per hour.

This week marks the best opportunity to reach the spacecraft, should it even be in condition to receive and process commands. If CONTOUR is in a flight attitude similar to what it was when it fired its solid rocket motor, the center of its most robust antenna - the multidirectional pancake beam - will be pointed at Earth.

APL manages the CONTOUR mission for NASA and built the spacecraft. Dr. Joseph Veverka, of Cornell University, Ithaca, N.Y., is CONTOUR's principal investigator.