New tech tracks space debris

Computing the complex orbital trajectories of spacecraft and space debris no longer requires the use of powerful supercomputers. A firm based in Lanham, Md., is using its own software and a computing cluster to model and predict the path of space debris and satellites for its U.S. government customers.

The company, A.I. Solutions, supports most of NASA’s satellite operations at the Goddard Space Flight Center. The company also conducts analyses for NASA prior to satellite launches. Other clients include the Air Force’s GPS program and collision avoidance work for rocket launches at the Kennedy Space Center in Florida. The company uses its FreeFlyer software application to provide satellite mission analysis. The firm teamed with Microsoft to combine FreeFlyer with the computing giant’s HPC tool.

According to Dave Rand, A.I. Solutions’ technology domain lead, FreeFlyer can perform debris modeling calculations, but only for one object or interaction per analysis. Combining it with Microsoft’s HPC tool permits the application to perform thousands of simultaneous orbital calculations. The software was combined to support NASA requirements to examine the long-term implications of the low orbit debris cloud created by the 2007 Chinese anti-satellite test, he said.

The company used the tool to map the trajectories of some 2,000 objects in the debris cloud. The first test of the system modeled the cloud out to 20 years and a second test predicted the cloud’s orbital path out to 100 years.

Orbital debris poses a serious threat to spacecraft. However, in the past, in-depth modeling and analysis was done only for manned space missions. A.I. Solutions' effort is the first time such an in-depth approach has been attempted for satellites. “The difference in what we did and what has been done to date is that what we did can really be considered high fidelity. When I say that, I mean we modeled each individual piece, and we modeled it very accurately in terms of its drag profile, in terms of how it’s going to come down through the atmosphere,” he said.

To track the debris, the company accessed data provided to NASA from U.S. Strategic Command. Rand added that previous attempts at debris modeling also did not benefit from access to high fidelity Defense Department data.

Lauri Kraft Newman, NASA’s robotic conjunction assessment manager at the Goddard Space Flight Center Robotic Systems Protection Office, said that agency analysts use the company’s FreeFlight application to pinpoint potential collisions. The software generates a risk analysis of any close encounter with an object in orbit. The data is then passed on to a human analyst for final consideration. NASA Goddard’s analysts track satellite conjunctions seven to 10 days in advance to provide several days advance notice in case an evasive maneuver is necessary.

She said that the company’s debris cloud modeling capability was also recently used to plot material created by the collision of two communications satellites, Iridium 33 and Cosmos 2251, in February 2009.

The company conducted this work without the use of specialized computers. Rand said that A.I. Solutions self-funded the initial work on the modeling capability by building its own computer to run the software. “We literally built our own cluster. It’s really very modest,” he said.

Rand said the hardware for specialized computing has become smaller, cheaper and more powerful. “It doesn’t take a lot of hardware and resources to do this any more. You don’t have to have a 1,000-core computer to do this, it can be 10 cores. The new hardware coupled with the software that automates it really gets you a long way,” Rand said. He cautioned that the system is still experimental and used for in-house research work and some emergency backup work.

The software is still maturing. Rand said that the company is improving the technology and added that the anti-satellite work was a pilot effort. Rand explained that the software is useful in jobs where a great deal of analysis must be conducted quickly. In its support role for NASA, the company maps the orbital outcomes for individual spacecraft. The software allows planners to run multiple scenarios over time to track the outcome of the vehicle’s mission.

“Instead of propagating thousands of things one time, we propagate one thing a thousand times,” he said.

This type of collision avoidance analysis has been conducted for decades. But the technology now allows this work to be conducted more often, less expensively and in more detail. Rand said that customers such as NASA are becoming more accustomed to having this analysis capability for their spacecraft.

The debris analysis software also saves time. Before the software and the HPC cluster, an orbital debris analysis would take about 30 days. With the cluster, the work is now done in about three days, providing the customer with a fast, cost effective turn around, he said.