An artist's concept of CONTOUR's rocket motor firing to leave Earth orbit. Photo: JHU-APL

Mission operators continue to scan the skies for the CONTOUR spacecraft, working through a list of strategies for re-establishing contact with the solar-powered probe through NASA's Deep Space Network (DSN).

"We're still trying to get a telemetry link," says CONTOUR Mission Director Dr. Robert Farquhar, of the Johns Hopkins University Applied Physics Laboratory, Laurel, Md. "We're trying to send commands to spacecraft to switch between its two transmitters and use different on-board antennas, in case they turned off for some reason. But we really won't know what happened until we contact it."

CONTOUR's STAR 30 solid-propellant rocket motor was programmed to ignite at 4:49 a.m. EDT and deliver a 1,920 meter-per-second boost that would send CONTOUR out of Earth's orbit and onto a path that would eventually take it past two comets. At about 140 miles (225 kilometers) above the Indian Ocean, the spacecraft was too low for DSN antennas to track it at the scheduled time of the burn. NASA's Jet Propulsion Laboratory, Pasadena, Calif, operates the DSN.

The CONTOUR mission operations team at the Johns Hopkins University Applied Physics Laboratory expected to regain contact at approximately 5:35 a.m. EDT to confirm the burn. When no signal was received, the team immediately began working through backup plans to re-establish contact, searching along the predicted trajectories for a successful burn.

"We're looking at the nominal path, as if the burn occurred," Farquhar says. "We're working on the assumption that the motor fired, and the team is putting its priority there."

CONTOUR's on-board computer is also carrying a command that, about 24 hours after the scheduled burn time, would turn the craft about 40 degrees and perhaps improve its antennas' fix on Earth. Farquhar adds that without knowing CONTOUR's status, it is difficult to know what commands it can, or did, execute. Still, he says, "we're cautiously optimistic that we will find the spacecraft."

CONTOUR, a Discovery-class mission to explore the nucleus of comets, was built and managed by the John Hopkins Laboratory Applied Physics Laboratory, Laurel, Md., for NASA.