Miniature Star Tracker Sparks Strong Interest

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WASHINGTON — Officials with AeroAstro Inc. are reporting widespread government and commercial interest in a miniature satellite orientation and pointing device the company is developing under a contract with the U.S. Air Force.

Manufacturers of large and small spacecraft, government agencies and even maritime fleet operators have approached AeroAstro to learn more about the Fast Angular Rate-Miniature Star Tracker (FAR-MST), said Tom Vaneck, vice president of business development at the Herndon, Va.-based space technology company.

“We’re getting two to three phone calls a week on this thing,” added Bill Seng, chief sensor systems engineer for AeroAstro.

Star trackers use the known positions of stars to help keep spacecraft properly oriented and pointed in the right direction. The FAR-MST effort is aimed at dramatically reducing the size, weight, power needs and cost of these devices, which would open up all kinds of options to spacecraft designers, AeroAstro officials said.

AeroAstro’s partner on the project is the Massachusetts Institute of Technology (MIT) of Cambridge, which is operating under a contract with the U.S. Missile Defense Agency. The device potentially has applications on missile interceptors as well as satellites, said Ray Sedwick , associate director of MIT’s Space Systems Laboratory.

MIT’s primary role in the project is to develop software algorithms that simplify the job that star trackers do. The idea, Sedwick said, is to deliver “as much performance as we can without being too computationally intensive.” Typical star trackers have built-in databases with locations of thousands of stars; the FAR-MST device will be able to function with a database of 500-600 stars, he said.

More than $1.5 million has been spent thus far on the project, Vaneck said. The current contract is expected to yield a prototype FAR-MST star tracker for laboratory testing, he said.

The ambitions for the project have grown since its inception two years ago, Vaneck said. As envisioned, the FAR-MST was supposed to take advantage of advances in electronics miniaturization to scale down the size of star trackers without fundamentally changing the way they operate.

“A lot of the star trackers on the market today are incredibly good, but they’re based on technologies which are years or possibly even decades old,” Vaneck said. “With the whole push in the electronics industry towards miniaturization, these technologies have gotten to the point where in terms of size and power consumption, you can make a really small star tracker.”

The Air Force recently modified AeroAstro’s contract to take the project one step further by eliminating ancillary star-tracker components such as gyroscopes, Seng said.

Project engineers say the combination of miniaturized electronics and exclusive reliance on optics will enable them to produce a fist-sized device weighing just 1 kilogram and using 3 watts of power. Comparable devices today weigh 5 to 10 kilograms and use 10-15 watts of power, Seng said.

Vaneck said star trackers based on the FAR-MST design will cost $100,000, compared to $500,000 to $750,000 for those in use today.

“Our philosophy is that we give you about 90 percent of the capability for about 10 percent of the cost,” Seng said.

Vaneck said the FAR-MST also will have a unique performance advantage in its ability to operate when the spacecraft is spinning at a relatively high rate. Many spacecraft maintain stability during and immediately after separating from their launch vehicle by spinning. The FAR-MST can begin to operate before the spin rate slows down substantially, reducing the time it takes to properly orient a newly deployed spacecraft, he said.

Because of its small size and low cost, the FAR-MST star tracker could serve not only as a primary pointing system on some spacecraft but also as a backup on others, Vaneck said. “That way if your device fails, the entire mission isn’t lost,” he said. “You may have reduced capabilities, but you still have a tracking device.”

Among the first potential customers for the FAR-MST device is the U.S. Naval Observatory, which would use it to help point a proposed space optical telescope known as the Milli-Arcsecond Pathfinder Survey, Seng said.

The mission, still in the pre-planning stages, would collect data to remap the celestial sphere and existing star catalogs, updating the work done by the European Space Agency’s Hipparcos satellite, he said.

Although there are firm plans for a flight demonstration, Vaneck expressed confidence that such an opportunity is forthcoming. “It has touched a nerve, and seems to be fitting a niche,” he said. “We’re confident we’ll be able to get a flight opportunity soon after phase two.”