Spacecraft use X-rays from dead stars to navigate spacecraft

(ORDO NEWS) — The remnants of destroyed neutron stars, called pulsars, have a magnetic charge and rotate at a speed of one to hundreds of revolutions per second.

These celestial bodies, each 19 to 24 kilometers in diameter, generate light in the X-ray wavelength range. Researchers at the University of Illinois Urbana-Champaign have developed a new way for spacecraft to use signals from multiple pulsars to navigate deep space.

“We can use star trackers to determine the direction of the spacecraft, but to know the exact location of the spacecraft, we rely on radio signals transmitted between the spacecraft and the Earth, which can take a long time and require the use of heavily loaded infrastructure, such as NASA’s Deep Space Network “said Zach Putnam, professor of aerospace engineering at Illinois.

“The use of X-ray navigation eliminates these two factors, but so far has required an initial estimate of the position of the spacecraft as a starting point. This study presents a system that finds candidates for possible positioning of the spacecraft without prior information, so that the spacecraft can navigate autonomously” .

“In addition, our ground communication systems for deep space missions are currently overloaded,” he said. This system will provide spacecraft autonomy and reduce dependence on the earth. “X-ray pulsar navigation allows us to get around this problem and determine where we are without calling the Earth.”

Because our atmosphere filters out all X-rays, Putnam says you need to be in space to see them. Pulsars emit electromagnetic radiation that looks like pulses as the pulsar rotates and sends them in our direction, like a beam of light thrown off by a beacon.

“Each pulsar has its own signature signal, like a fingerprint,” he said. ”

Like the Global Positioning System, location can be determined from the intersection of three signals.

“The problem with pulsars is that they spin so fast that the signal repeats very often,” he said. “By comparison, GPS satellites also line up every two weeks. Although there are an infinite number of possible locations for spacecraft, we know how far apart these objects are.

“We are trying to determine the position of spacecraft in areas that are on the order of a few astronomical units in diameter, for example, the size of the orbit of Jupiter is something like a square with a side of one and a half billion kilometers.

The problem we are trying to solve is how to intelligently observe pulsars and fully determine all possible spacecraft locations without using excessive amounts of computing resources,” Putnam said.

An algorithm developed by graduate student Kevin Lohan combines observations of multiple pulsars to determine all possible positions for a spacecraft. The algorithm handles all possible intersections in two or three dimensions.

“We used an algorithm to learn which pulsars we should use to reduce the number of possible locations in a given area,” Putnam said. The results showed that observing sets of pulsars with longer periods and smaller angular distances can significantly reduce the number of pulsars in a given domain.

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