Innovative Use of Heliostats: Spotting Asteroids at Night

In a groundbreaking proposal, Dr. John Sandusky from Sandia National Laboratories suggests that heliostats, which are traditionally used in solar thermal power plants, could be repurposed to identify near-Earth objects (NEOs) during nighttime. Heliostats, devices that focus sunlight to generate electricity, have fallen behind photovoltaic panels in commercial viability. However, their capability to maintain heat after sunset gives them a unique advantage that might be leveraged for astronomical observations.

Dr. Sandusky articulated this innovative idea in an interview with the Sandia newsletter LabNews, emphasizing the untapped potential of heliostats, which currently remain dormant during the night. "The nation has an opportunity to give them a night job at a relatively low cost for finding near-Earth objects," he said, underscoring the importance of early detection of asteroids to mitigate potential threats to Earth.

The concept stems from a test conducted with one of the 212 heliostats at the National Solar Thermal Test Facility. In this initial experiment, Dr. Sandusky programmed the heliostat to move in a sweeping motion, allowing it to capture and focus starlight. Unlike traditional asteroid detection methods that rely on large telescopes to observe specific areas of the sky, this approach could potentially allow for a more comprehensive surveillance of celestial objects. Dr. Sandusky noted, "If we knew ahead of time that an asteroid was coming and where it might hit, we’d have a better chance to prepare and reduce the potential damage."

Asteroid detection has significantly improved in recent years, with advancements in technology enabling the identification of objects that move relative to the stars. The Vera C. Rubin Observatory, scheduled to begin operations soon, is expected to enhance this capability even further. However, Sandusky suggests that utilizing heliostats could free up these giant telescopes for other research roles, thereby expanding the horizons of both asteroid detection and astronomical research.

The heliostat's ability to reflect light might allow for the detection of asteroids by analyzing the light scattered off their surfaces. "Solar towers collect a million watts of sunlight," Dr. Sandusky explained. "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."

While Dr. Sandusky's initial tests did not lead to the discovery of any asteroids, he viewed the experiment as a success in proving that heliostats could be effectively utilized for this purpose. He is now seeking feedback from peers in the optics and asteroid hunting communities to refine this approach further. "Getting peer feedback provides an opportunity to understand what the concerns are about how this technology will work," he stated.

Interestingly, the idea was inspired by a question posed to Dr. Sandusky two decades ago regarding the imaging capabilities of heliostats. Initially dismissing the notion due to the optical quality of the devices, he has revisited the concept, finding parallels between the reflections of objects moving in relation to stars and frequency shifts used in radio communications. This linkage has opened new avenues for potential applications of heliostats beyond their traditional role in solar energy.

As the research continues, Dr. Sandusky has also proposed innovative uses for heliostats in locating lost spacecraft, particularly those orbiting between Earth and the Moon. He highlighted that tracking these objects can be challenging from the ground, suggesting that heliostats could play a role in expanding our ability to monitor space debris and other celestial phenomena.

While the economic viability of employing heliostats for such astronomical tasks remains uncertain, the exploration of their nighttime utility marks an intriguing intersection of renewable energy technology and space exploration. The findings from Dr. Sandusky’s work were published in the proceedings of the Optical Engineering and Applications conference, titled "Unconventional Imaging, Sensing and Adaptive Optics". As the scientific community considers the implications of this innovative approach, the future of asteroid detection could be poised for significant advancements, leveraging existing technologies in novel ways.