Proposed spacecraft navigation uses x-rays from dead stars

Date:
May 3, 2022
Source:
University of Illinois Grainger College of Engineering
Summary:
The remnants of a collapsed neutron star, called a pulsar, are
magnetically charged and spinning anywhere from one rotation
per second to hundreds of rotations per second. These celestial
bodies, each 12 to 15 miles in diameter, generate light in the
x-ray wavelength range.

Researchers have developed a new way spacecraft can use signals
from multiple pulsars to navigate in deep space.



FULL STORY ==========================================================================
The remnants of a collapsed neutron star, called a pulsar, are
magnetically charged and spinning anywhere from one rotation per
second to hundreds of rotations per second. These celestial bodies,
each 12 to 15 miles in diameter, generate light in the x-ray wavelength
range. Researchers at The Grainger College of Engineering, University of Illinois Urbana-Champaign developed a new way spacecraft can use signals
from multiple pulsars to navigate in deep space.


==========================================================================
"We can use star trackers to determine the direction a spacecraft is
pointing, but to learn the precise location of the spacecraft, we rely
on radio signals sent between the spacecraft and the Earth, which can
take a lot of time and requires use of oversubscribed infrastructure,
like NASA's Deep Space Network," said Zach Putnam, professor in the
Department of Aerospace Engineering at Illinois.

"Using x-ray navigation eliminates those two factors, but until now,
required an initial position estimate of the spacecraft as a starting
point. This research presents a system that finds candidates for possible spacecraft locations without prior information, so the spacecraft can
navigate autonomously." "Also, our ground communication systems for deep
space missions are overloaded right now," he said. "This system would give spacecraft autonomy and reduce the dependency on the ground. X-ray pulsar navigation gets us around that and allows us to determine where we are,
without calling." Putnam said because our atmosphere filters out all
the x-rays, you have to be in space to observe them. The pulsars emit electromagnetic radiation that look like pulses because we measure the
peak in the x-ray signals every time the pulsar spins around and points
toward us -- like the ray of light cast from the beacon on a lighthouse.

"Each pulsar has its own characteristic signal, like a fingerprint,"
he said.

"We have records of the x-rays over time from the 2,000 or so pulsars
and how they've changed over time." Much like the Global Positioning
System, location can be determined from intersection of three signals.

"The issue with pulsars is that they spin so fast that the signal
repeats itself a lot," he said. "By comparison, GPS repeats every two
weeks. With pulsars, while there are an infinite number of possible
spacecraft locations, we know how far apart these candidate locations
are from each other.

"We are looking at determining spacecraft position within domains that
have diameters on the order of multiple astronomical units, like the
size of the orbit of Jupiter -- something like a square with one billion
miles on a side.

The challenge we are trying to address is, how do we intelligently observe pulsars and fully determine all possible spacecraft locations in a domain without using an excessive amount of compute resources," Putnam said.

The algorithm developed by graduate student Kevin Lohan combines
observations from numerous pulsars to determine all the possible positions
of the spacecraft. The algorithm processes all the candidate intersections
in two dimensions or three dimensions.

"We used the algorithm to study which pulsars we should observe to reduce
the number of candidate spacecraft locations within a given domain,"
said Putnam.

Results showed that observing sets of pulsars with longer periods and
small angular separations could significantly reduce the number of
candidate solutions within a given domain.

The research was funded in part by NASA.


========================================================================== Story Source: Materials provided by University_of_Illinois_Grainger_College_of_Engineering.

Original written by Debra Levey Larson. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Kevin Lohan, Zachary Putnam. Characterization of Candidate
Solutions for
X-Ray Pulsar Navigation. IEEE Transactions on Aerospace and
Electronic Systems, 2022; 1 DOI: 10.1109/TAES.2022.3152684 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/05/220503141334.htm

--- up 9 weeks, 1 day, 10 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)