Marshall Ponders Debris Tracking Demo Satellite

by

WASHINGTON — NASA’s Marshall Space Flight Center is gathering information for the possible development of a demonstration satellite to track pieces of orbital debris that are too small to be seen by current systems but still pose a threat to operating spacecraft.

Spurred by the new U.S. National Space Policy that emphasizes tracking and mitigating orbital debris, Huntsville, Ala.-based Marshall may partner with industry and academia to field a low Earth orbiting satellite as soon as 2014, said Bruce Wiegmann, an engineer in Marshall’s Advanced Concepts Office.

In the last decade, orbital debris has become a serious concern for spacefaring nations, with several high-profile events drastically increasing the amount of junk circling the Earth. China was widely criticized for shooting down one of its one weather satellites in 2007. Then in 2009, an operational Iridium communications satellite collided with a defunct Russian communications satellite. These two events increased the estimated number of pieces of small debris in low Earth orbit from 300,000 to 500,000, Wiegmann said in an Oct. 19 interview.

The U.S. Air Force has a mandate to catalog and track objects in Earth orbit with its network of ground radars, optical telescopes and the new Space Based Space Surveillance (SBSS) optical satellite that was launched in September. But the Air Force’s systems can track only the 11,000 or so objects in space that are 10 centimeters in size or larger.

There have been five or six incidents, mostly in the 1990s, in which space debris is believed to have caused the degradation or failure of satellites on orbit, though without more sensitive tracking capabilities this is impossible to know for sure, Wiegmann said.

“We decided to look at the small debris because it’s a hard problem and it’s untracked,” Wiegmann said.

In a notice posted Oct. 6 on the Federal Business Opportunities website, Marshall said it is seeking information for a potential demonstration satellite to track small debris in low Earth orbit and described a “straw man” set of requirements for the mission. Responses are due Oct. 27.

The satellite would use an optical, infrared, ultraviolet or other type of payload weighing between 100 and 200 kilograms and a platform weighing between 400 and 500 kilograms, the posting said. The satellite would launch around 2014 or 2015 on a Falcon 1e- or Minotaur 4-class U.S. rocket into a near-polar circular orbit between 800 and 850 kilometers high. It would be able to track objects between 1 and 10 centimeters in size from a distance of 1,000 kilometers, it said.

Marshall began drafting the mission concept in response to the U.S. National Space Policy issued June 28, Wiegmann said. The policy directs U.S. agencies to continue development and adoption of policies to minimize the creation of space debris; to develop and maintain systems for identifying and attributing actions in space; and to pursue research and development techniques and technologies to mitigate and remove on-orbit debris.

There are many challenges in tracking small pieces of debris, not the least of which is the great relative speed at which many of these pieces are traveling, which can exceed 15 kilometers per second, Wiegmann said. The albedo, or reflectivity of light, that debris has is also an issue because it widely varies depending on the type of object. This will be one factor in choosing the type of sensor, he said. The sheer quantity of debris in some orbits likely will make it necessary to have a sensor with a very limited field of view, one that perhaps observes only tens of pieces per day, he said.

Though the mission requirements are challenging, NASA and U.S. industry and academic institutions have the technology and engineering chops to get it done, Wiegmann said.

“You can’t do any type of debris removal until you can track it well,” he said. “A lot of people say it’s very hard to track the stuff. Just because it’s hard doesn’t mean you can’t do it. Let’s have the old American ingenuity and say, ‘We’re going to do it, and we’re going to do it within three years.’ It’s not that hard.”