Air Force ANGELS: Satellite Escorts to Take Flight
Launched in April, the Air Force XSS-11 micro-satellite is testing technologies useful for space servicing and inspection – capabilities helpful for both military and civilian objectives. Image
Credit: Air Force Research Laboratory (AFRL)

The U.S. Air Force Research Laboratory is planning a small experimental satellite that would orbit in close proximity to a host spacecraft and keep tabs on their surrounding space environment.

The laboratory's space vehicles directorate, located at Kirtland Air Force Base in New Mexico, plans to fly the experiment in 2009, according to a request for information sent to industry Nov. 15.

Plans call for awarding up to three study contracts for the Autonomous Nanosatellite Guardian for Evaluating Local Space (Angels) this coming spring, said Tom Caudill, the space surveillance technical area lead at the laboratory. A single company likely would be chosen in 2007 to build the demonstration spacecraft, he said.

Caudill acknowledged the program's schedule and $20 million budget are challenging. But he said those constraints were chosen deliberately to help stimulate designs for relatively simple, low-cost satellites that can be built quickly, he said.

"We're trying to change the paradigm--to push contractors to do this quicker and cheaper," Caudill said, noting that the military is making a developmental push in this direction with efforts like TacSat.

The Angels satellite will be launched into a geostationary orbit for an experiment that is expected to last about a year, according to the request for information. The Air Force hopes to extend the mission for another two years, according to the request for information.

Geostationary orbit is a belt of space some 36,000 kilometers above the equator that hosts most communications satellites. The Air Force chose that orbit because its distance from Earth's surface makes it less visible and more difficult to monitor than lower orbits, Caudill said.

The Angels spacecraft would launch along with a yet-to-be-determined host satellite that it would shadow in orbit, Caudill said. The launch likely will be arranged by the Defense Department's Space Test Program, he said.

Caudill said a full range of contractors, large and small, have expressed interest in the Angels project. "The smaller firms are maybe a little more able to live within the cost than the bigger ones, but even the big houses are looking seriously at what they can do to make this work," he said.

Prospective contractors will be given the chance to define much of the satellite's capability, Caudill said. Those capabilities could include monitoring space weather conditions, detecting anti-satellite weapons and diagnosing technical problems with the host spacecraft, he said.

Bidders must use relatively mature technology for the Angels program, Caudill said. Individual component technologies must be proven by the time bids are submitted in May 2007, and their ability to operate as part of an integrated system must be demonstrated by December 2008, he said.

The Air Force Research Laboratory's work on small orbit-rendezvous satellites such as XSS-10 and XSS-11, as well as advances in component miniaturization, have helped lay the groundwork for Angels, Caudill said.

Meanwhile, the lab also is working on an experimental space-based optical telescope that could monitor distant objects in space, according to the request for information.

Caudill said that effort is not as far along as Angels, but that the telescope would be mounted on a significantly larger satellite, though one that is smaller than most platforms used by the Air Force today.

Theresa Hitchens, director of the Center for Defense Information, a think tank here, said better space surveillance capabilities are urgently needed by the Air Force.

"It needs to be done and pronto," she said. Hitchens in the past has called for improvements to U.S. space surveillance systems to help U.S. satellites avoid collisions with other spacecraft as well as orbital debris.

But Hitchens also sees potential problems with a mission in which one satellite closely shadows another. If a spacecraft were to stray too far from its host it could be viewed as a threat by other nations operating satellites in the area, she said.

"If the Chinese were doing this, you can bet that the U.S. Air Force would be apoplectic," Hitchens said.