"Heliostat fields don't have a night job. They just sit there unused," said Sandusky. "The nation has an opportunity to give them a night job at a relatively low cost for finding near-Earth objects." The approach could improve early detection and response to potential asteroid impacts.
Traditional asteroid searches rely on observatory-grade telescopes to capture images of the night sky. Computers then analyze these images for faint streaks that indicate asteroids. However, this method is resource-intensive and slow, and constructing new observatories requires significant investment.
As part of a Laboratory Directed Research and Development project, Sandusky conducted nighttime tests at the National Solar Thermal Test Facility using a single heliostat from a 212-unit field. Rather than modifying the mirror with specialized equipment, he used existing software to slowly oscillate its direction relative to the stars - sweeping back and forth once per minute.
"Solar towers collect a million watts of sunlight," said Sandusky. "At night, we want to collect a femtowatt, which is a millionth of a billionth of a watt of power of sunlight that's scattered off of asteroids."
By tracking the speed at which objects move in relation to the stars, Sandusky aims to detect asteroids not through images, but through motion - an unconventional but potentially efficient approach.
During the trial, Sandusky climbed the 200-foot solar tower at dusk and used standard optical tools to measure the light the heliostat focused on the tower. Data was gathered at roughly 20-minute intervals throughout the night.
The experiment did not attempt to discover asteroids but successfully demonstrated the ability to sweep the heliostat and detect starlight, establishing proof of concept.
According to Sandusky, the potential benefits go beyond asteroid detection. The technology could support U.S. Space Force efforts to monitor spacecraft, particularly in challenging orbits near the moon.
He shared results with the International Society for Optics and Photonics and is seeking input from experts. "We want to hear from our peers in optics and the asteroid hunting community," he said. "Getting peer feedback provides an opportunity to understand what the concerns are about how this technology will work."
Future work could include tracking a known planet to test accuracy and gradually scaling up from one heliostat to many in hopes of detecting smaller and fainter near-Earth objects.
"We're looking for opportunities to scale up from one heliostat to many and try to demonstrate that we can help find near-Earth objects," Sandusky said. "We also want to demonstrate we can scale up the technology to detect even smaller asteroids."
Related Links
Laboratory Directed Research and Development
Asteroid and Comet Mission News, Science and Technology
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