The U.S. space agency is planning to conduct its first completely automated rendezvous in space Tuesday. In a test of new technology, a spacecraft is scheduled to be launched to track and meet an orbiting satellite with no human intervention, a capability now enjoyed only by Russia.
Every U.S. rendezvous and docking in space over the last 40 years has required the guiding hands of astronauts. In contrast, Russian Soyuz crew vehicles and Progress cargo rockets routinely mate with the international space station automatically.
Now the U.S. space agency NASA is looking ahead to the time when its manned space shuttles stop visiting the station in six years and when robot supply ships are needed to service bases on the moon or Mars.
To demonstrate the technology to do this, an autonomous spacecraft named DART will be carried into space by a Pegasus rocket after both are dropped from the wing of a jet aircraft high over the Pacific Ocean. Once released, DART will use only its computers and sensors to rendezvous with a retired U.S. military communications satellite.
"DART is basically the technology to put two objects together in space," said James Snoddy, manager of the DART project. "What we've done with DART is we've basically created an eye, which we call an Advanced Video Guidance Sensor, to be able to locate an object in space. We've also created what we call a brain, which has the ability to run all the guidance and control schemes in space without any human intervention."
The DART spacecraft is to guide itself to the vicinity of the target satellite with the help of a network of other satellites known as the Global Positioning System. The Global Positioning System relays data that the target satellite itself transmits about its location. As DART approaches the satellite, it own laser beam eye takes over the search. Mr. Snoddy says that once DART has located the satellite, it is to make a series of intricate maneuvers around it before closing in to a distance of five meters.
"We're basically pretty excited about being able to turn DART and let autopilot go and it's going to be an interesting mission where you really have no control of your mission once you let go of it, but that's what the technology is all about," he said. "One day this will allow for total autonomous operations in space."
The DART spacecraft will not dock during this demonstration because the target satellite was not designed for docking. But Mr. Snoddy says DART is precise enough to be able to attach to its target within a tolerance of only millimeters.
The technology will get its chance to prove itself in a series of actual dockings in two years. NASA and the U.S. military have joined forces to develop another autonomous spacecraft capable of refueling and servicing satellites. Beginning in late 2006, it will conduct several docking and refueling exercises and robotic transfers.
Such a craft could even be used to service the Hubble Space Telescope in 2007 or later now that NASA has decided not to send astronauts on such a mission.
Mr. Snoddy says even when a mission is manned, the technology would also be useful as an autopilot.
"Even the human eye has some error in it," he said. "An autopilot is a great thing to have to measure the distance and bring me precisely in to dock."