Robotics to Refuel, Fix Satellites

type size: [A] [A] [A]

March 9, 2007 — Satellite out of fuel? Spacecraft batteries on the fritz? If tests of a newly launched robotic system prove fruitful, aging satellites should be in position for a very productive afterlife.

"What we're really trying to do is change the paradigm of how we operate in space," said Fred Kennedy, who manages the $300-million Defense Advanced Research Projects Agency prototype, which is called Orbital Express.

With few exceptions, such as the Hubble Space Telescope, which was designed for in-flight servicing by space shuttle crews, spacecraft need to have everything aboard at the time they are launched. Once a key component breaks down, or when maneuvering fuel runs out, the satellites are dead.

Orbital Express will attempt to change that. The program's two spacecraft were among six small research satellites launched aboard an unmanned Atlas 5 rocket Thursday night from Cape Canaveral Air Force Station in Florida.

The technology, which was developed by the U.S. military in cooperation with NASA, is intended to extend the lives of spy satellites, lay the groundwork for servicing and repairs of government-owned spacecraft and telescopes after the space shuttle fleet is retired and seed new technologies of interest to commercial spacecraft manufacturers and operators.

"If we're able to, for instance, refuel satellites, a mission designer will not have to simply tag all the fuel he needs onto the vehicle right away. He can think about how he might do something with that later on. Five years downstream, Orbital Express will come along, provide propellant and he'll get new life out of the system," Kennedy said.

Orbital Express includes a 2,100-pound servicing robot and a small, next-generation satellite built for in-flight refueling and maintenance. After a thorough systems checkout, Orbital Express will begin a series of demonstrations that are expected to last at least three months.

The servicing craft, called ASTRO — an acronym for Autonomous Space Transport Robotic Operations — is filled with about 300 pounds of hydrazine propellant and includes a small robot arm to latch onto or pass over equipment to its partner spacecraft, known as NextSat.

The first tests involve fuel transfers and will take place while the two vehicles are still attached to each other, which is how they were launched.

After that, ASTRO will separate from NextSat and begin using a NASA-developed autonomous navigation system to maneuver. A similar system was tested two years ago aboard NASA's Demonstration of Autonomous Rendezvous Technology (DART) satellite, but the spacecraft collided with its target, ending the mission.

ASTRO navigates by shoots infrared laser beams at NextSat and analyzing the light that bounces back off a pattern of retroreflectors on the satellites. ASTRO then can adjust its speed and angle of approach. Eight demonstrations are planned, with ASTRO moving as far as seven kilometers, or 4.3 miles, from NextSat.

"When we get to that point, I'll be pretty relieved," Kennedy said.

Unlike DART, ground control teams for Orbital Express will be able to step in and stop the spacecraft if it looks like it is getting into trouble.

Among the tasks set during the Orbital Express mission are: transferring and hooking up a 53-pound battery, switching between a primary and backup computer, grasping and maneuvering NextSat and testing a series of rendezvous and capture techniques.

"We're trying out brand new technology," said Carol Welsch, director of Kirtland Air Force Base's Space Development Group, which put together the six-satellite Space Test Program mission that includes Orbital Express.

"Quite honestly, some of these are very challenging technologies and they may not work," she said.

Sharing the ride to space with Orbital Express were four science satellites:

*The Cibola Flight Experiment is intended to test new power supplies, inflatable antennas and other technologies being designed for future satellites.

* FalconSat 3, which was built by students at the U.S. Air Force Academy, has five experiments to study space weather and spacecraft operations.

*MidSTAR-1, built by the U.S. Naval Academy, will test a variety of miniature sensors, as well as an internet communications system.

*Space Test Program Satellite-1 includes experiments to test space-to-ground communications and assess a high-resolution ultraviolet spectrometer.

All the spacecraft were released into their intended orbits, a process that took the Atlas rocket and its upper-stage engine more than an hour to accomplish after its 10:10 p.m. EST liftoff.

"(The payloads) required an extraordinary level of coordination and innovation to achieve the mission requirements," Jim Sponnick, vice president of Atlas programs for United Launch Alliance, said after the last spacecraft was released into orbit.

"The fact that the Atlas system performed so well tonight in delivering the six satellites to their prescribed orbits is a tribute to the teamwork between our Air Force customer, the Space Development and Test Wing, and men and women of the ULA team," he said.