A NASA robotic spacecraft located a Pentagon satellite in space without any help from human controllers, but the mission ended early when the computer-driven craft detected a fuel problem, the mission manager said Saturday.
The experimental DART spacecraft — short for Demonstration of Autonomous Rendezvous Technology — had moved to within 300 feet of the satellite orbiting 472 miles above the Earth but backed off late Friday, about 11 hours into the mission, manager Jim Snoddy said.
The spacecraft was supposed to have maneuvered around the satellite, getting as close as 15 feet, for another 12 hours. After the problem arose, the 800-pound craft began coasting; it will eventually disintegrate in orbit.
“When we started doing precise maneuvers, we started seeing excessive propellant consumption. ... It went south pretty quickly,” Snoddy said. “The mission as designed, when it runs out of gas, completes itself.”
There were some navigation errors but no indication of a fuel leak, he said in a conference call. A NASA investigation board will search for the cause of the problem.
‘You have to be perfect in space’
Snoddy called the mission a partial success because it demonstrated that an entirely computer-controlled craft could find a satellite in space.
“We’ve done what nobody’s ever tried to do before,” he said. “A lot of things worked well on the ground. The real truth is you have to be perfect in space. ... There was obviously something we didn’t model.”
The $110 million mission, classified as high-risk because of its automated controls and relatively low budget, was intended to help lay the groundwork for future projects like robotic delivery of cargo to space shuttles and automated docking and repair between spacecraft in orbit.
The main instrument on the craft was a next-generation combination of optics and electronics called an advanced video guidance sensor. The sensor, which was to have been used to steer DART closer to the satellite, is a more sophisticated version of one tested during space shuttle flights.
“We were really excited to go and show that we could drive this in and go back out,” Snoddy said. But, he added: “The brain of DART told it, ‘Hey you don’t have time to do this anymore.”’
Mission a qualified success
The company that built the craft, Dulles, Va.-based Orbital Sciences Corp., said it was disappointed in the outcome but pleased with the first part of the mission.
“For the amount that DART did do, was able to get done, we’re proud of that,” spokesman Barry Beneski said. “However, we clearly would like to have seen the mission go its full extent.”
The DART spacecraft was launched from an aircraft Friday morning. The mission originated at Vandenberg Air Force Base and was managed by NASA’s Marshall Space Flight Center in Huntsville, Ala.
The Pentagon satellite that was the target of the mission was launched in 1999 and carries special reflectors that are used by guidance systems such as the one aboard DART.
