NASA Tracks Navigation Errors, Fuel Shortage in DART Rendezvous Mission

by Chris Kridler, FLORIDA TODAY

Date: 16 April 2005 Time: 04:17 PM ET

DART, an $110 million experimental space mission designed to test automated docking technology, ended prematurely late Friday after its launch from Vandenberg Air Force Base in California, NASA said today.

NASA's DART (Demonstration of Automated Rendezvous Technology) was launched Friday at 1:25 p.m. EDT from a Pegasus rocket, which was released from a Stargazer L-1011 aircraft at 40,000 feet over the Pacific Ocean.

Click here for a blow-by-blow account of DART's launch and 24-hour mission.

The first sign of anything unusual was during on-orbit checkouts, when ground controllers saw higher than anticipated navigation errors, project manager Jim Snoddy said today.

During the subsequent rendezvous phase, "everything was working wonderful," he said. "We had high accuracy."

In orbit, DART was to fly around the Earth and rendezvous with an experimental communications satellite launched in 1999. It was to get about 16 feet from the satellite and perform several up-close maneuvers using a guidance sensor aboard DART and Global Positioning System satellite navigation information.

The 800-pound DART successfully met up with its target satellite and approached within about 300 feet, but managers noticed it was using fuel too fast.

The guidance system sensed the empty fuel tank and commanded the spacecraft to retreat and enter the safe orbit that should lead it to burn up in the atmosphere within 10 years, Snoddy said.

DART was executing an engine burn that would put it in that orbit today.

Snoddy wouldn't speculate why the craft lost fuel so quickly -- it started with enough to do all its maneuvers twice, plus a 30 percent margin -- but said managers had not seen evidence of a leak.

NASA is forming a mishap investigation board to look into the failure.

Snoddy said some of DART's technology was proven in the aborted mission, but not the critical maneuvers that would demonstrate the ability of a spacecraft to dock without human intervention.

"We've done what nobody's ever tried to do before," Snoddy said of DART, which was "high risk" in that, to save money, it had limited ability to communicate or fix problems on the fly during its planned 24-hour mission.

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