Science

NASA updates its asteroid hazard software to use sunlight

NASA’s Jet Propulsion Laboratory (JPL) has just updated the software it uses to assess potentially dangerous asteroids to account for the effect of sunlight on orbits, among other changes.

While there are no known immediate space rock dangers to Earth despite decades of careful searching, astronomers continue to scan the skies, just in case. The new impact monitoring algorithm, called Sentry-II, updates software in use for 20 years.

Like its Sentry predecessor, the new Sentry-II will periodically scan a table of potentially hazardous asteroids with known orbits, generated by the JPL-run Center for Near-Earth Object Studies.

Photos: Asteroids in deep space

Sentry-II will make calculations for at least the next decade, reporting the objects with calculated orbits that are most at risk to Earth. (Another system called Scout evaluates those asteroids with only partially known orbits.)

But Sentry-II also includes a key update that will make your assessments more accurate: taking the Yarkovsky effect into account.

The Yarkovsky effect occurs when the asteroid’s surface absorbs sunlight and re-emits it as heat. This heat emission has a subtle but powerful effect on an asteroid’s path through space and can affect the probability of the space rock hitting Earth.

Astronomers have known about the Yarkovsky effect for decades, yet only recently has computer software become powerful enough to handle analysis of the effect on large data sets. Sentry-II will allow JPL to assess potential hits with probabilities as small as a few chances in 10 million, the agency said.

“The fact that Sentry could not automatically handle the Yarkovsky effect was a limitation,” Davide Farnocchia, a JPL navigation engineer who also helped develop Sentry-II, said in a statement.

The lack of Yarkovsky calculations in the original Sentry system meant that astrophysicists had to do manual analysis every time they encountered a “special case” asteroid, Farnocchia noted. One of the most famous examples was the asteroid Apophis, which required a manual assessment of the Yarkovsky effect to determine how likely an impact by this asteroid was in 2068. Fortunately, last year, NASA determined that the Apophis flyby in 2068 will be harmless.

Artist's illustration of NASA's asteroid-hunting NEO Surveyor spacecraft in space.

Artist’s illustration of NASA’s asteroid-hunting NEO Surveyor spacecraft in space. (Image credit: NASA/JPL-Caltech)

The previous system also had another limitation, in that it couldn’t always predict the impact probability of asteroids swinging extremely close to Earth. Sentry-II allows for a more robust set of calculations that accounts for the significant effect Earth’s gravity has in such situations, NASA said.

Additionally, Sentry-II predicts orbits with fewer guesses about which ones an asteroid is most likely to take, allowing the algorithm to find low-probability impact scenarios that its predecessor might have missed.

Sentry-II will become a reality as larger and more capable survey telescopes come online in the next decade, NASA said. There are nearly 28,000 known near-Earth asteroids and observatories are already adding more discoveries at a rate of about 3,000 a year, NASA said. This rate of discovery will accelerate as the decade progresses.

Among those new observatories will be the Near-Earth Object (NEO) Surveyor mission, whose expected launch in 2026 will finally provide a spacecraft dedicated to searching for asteroids. NEO Surveyor is expected to discover 90% of near-Earth asteroids 460 feet (140 meters) in size or larger within a decade of its launch.

Another highly anticipated asteroid hunting observatory, based in Chile, is the Vera C. Rubin Observatory. Formerly known as the Large Synoptic Survey Telescope, Rubin is expected to see first light in July 2023. The US National Science Foundation funded Rubin to, among other tasks, search for potentially dangerous asteroids by observing the same area. of the sky every hour, looking for objects that changed position.

A study describing Sentry-II was published in the Astronomical Journal on December 1, 2021.

Follow Elizabeth Howell on Twitter @howellspace. Follow us on Twitter @Spacedotcom and on Facebook.

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