Military microsatellite looks in on spacecraft

By Leonard David

Senior space writer

updated 5:19 p.m. ET July 22, 2005

The U.S. Air Force is utilizing a small spacecraft to explore a range of future military applications such as in-space servicing and repair, as well as close-up inspection of satellites in support of future space operations.

Rocketed into space on April 11 from Vandenberg Air Force Base in California on a Minotaur booster provided by Orbital Sciences, the XSS-11 (Experimental Satellite System-11) has been busily undergoing a step-by-step system shakeout.

The micro-spacecraft tips the scales at roughly 220 pounds (100 kilograms) and is about the size of a dishwasher, with outstretched solar panels.

The Air Force Research Laboratory’s Space Vehicles Directorate at Kirtland Air Force Base in New Mexico developed the XSS-11. Small, low-cost satellites such as XSS-11 are being tapped to demonstrate key capabilities, from autonomous mission planning, rendezvous and proximity operations to other functions that add to the U.S. military’s space toolkit.

In showcasing its skills, the XSS-11 is to exhibit the ability for autonomous planning and rendezvous with approved space objects near the satellite’s orbit. During its mission, projected to last a year to 18 months, the satellite will rendezvous with several U.S.-owned objects in its orbit — inactive or dead research satellites or old rocket stages.

Not schedule-driven
XSS-11 is now closing in on its first object — a revisit, actually, of the Minotaur fourth stage that dropped the spacecraft off in space.

"The spacecraft is in very good health," reported Harold "Vern" Baker, AFRL’s XSS-11 program manager. "All our sensors at the component level have checked out. Everything is working well."

The XSS-11 is circling Earth at an altitude of 500 to 530 miles (800 to 850 kilometers).

Baker said the ground operators are moving very cautiously and safely. "We are not schedule-driven," he told SPACE.com in a phone interview. Thanks to miniaturization of items such as communications hardware and cameras, there are a number of missions that can be accomplished via microsatellite, duties that would have involved much larger spacecraft in the past, he explained.

The XSS-11 is headed toward the Minotaur upper stage. The project team is taking incremental box steps to move in closer and closer as they gain more confidence in the spacecraft’s performance. At present, visual imager and range sensor equipment on the satellite is being evaluated.

Safety first
"We are staying a good ways away from it [the upper stage] … making sure that everything is performing the way we expect," Baker said. Arrival at the spent rocket stage is likely within the next few weeks, he said.

Initially, the XSS-11 is to stay in front of or well behind the object from far away. Then the spacecraft would circumnavigate the stage. The plan is to come within less than a mile to 1.2 miles (1 to 2 kilometers) of the spent rocket body.

Orbiting space hardware that could come into the up-close and personal sights of XSS-11 are other derelict rocket bodies and several old satellites — all U.S.-owned dead or inactive property, Baker emphasized. "We don’t call them targets … they are space objects."

"It’s all based on space safety and making sure we don’t run into something. Like I have said many times, if we hit we fail," Baker added. "If we were to bump into anything … there wouldn’t be a loss of value to somebody."

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