DART: NASA’s Defense System Against Asteroids Uses Clever Algorithm to Predict Incoming Threat

The new technique enhances NASA JPL’s Center for Near Earth Object Studies’ ability to analyze the impact danger of asteroids approaching our planet.


(Photo : MasterTux on Pixabay)

Nearly 28,000 near-Earth asteroids (NEAs) have been discovered so far using survey telescopes that continuously monitor the night sky, with roughly 3,000 discoveries every year. Over the next several years, however, as larger and more powerful survey telescopes turbocharge the search, a substantial spike in findings is projected.

NASA scientists have created Sentry-II, a next-generation impact monitoring algorithm, better to analyze NEA impact probability in anticipation of this rise

Asteroids are frequently depicted in popular culture as chaotic objects that speed carelessly through our solar system, changing course unpredictably and posing a threat to our planet at any time. This is far from the case. Asteroids are celestial bodies that follow well-defined orbital routes around the Sun and obey the rules of physics.

However, such routes can occasionally approach incredibly near to Earth’s future position. Experts cannot entirely rule out a future Earth impact due to slight uncertainties in the asteroids’ placements. As a result, astronomers employ advanced impact monitoring algorithms to determine the impact risk automatically.

DART is a planetary defense-driven test of technology to prevent an asteroid from colliding with Earth. DART will be the first time a kinetic impactor will be used to alter an asteroid’s velocity in space. The DART mission is directed by APL and administered at Marshall Space Flight Center for NASA’s Planetary Defense Coordination Office and the Science Mission Directorate’s Planetary Science Division at NASA Headquarters in Washington, DC, under NASA’s Solar System Exploration Program.

Related Article: NASA Plans to Deflect Asteroids to Defend the Planet from Cosmic Disaster

SENTRY Algorithm

Asteroid belt landscape

(Photo : Wikimedia Commons)

The Center for Near Earth Object Studies (CNEOS), managed by NASA’s Jet Propulsion Laboratory in Southern California, calculates every known NEA orbit to enhance impact hazard estimates supporting NASA’s Planetary Defense Coordination Office (PDCO). CNEOS has used the Sentry software, created by JPL in 2002, to monitor the impact danger presented by NEAs.

“The first version of Sentry was a highly sophisticated system that was in service for about 20 years,” said Javier Roa Vicens, a navigation engineer at JPL. They just went to SpaceX and spearheaded the development of Sentry-II. “It was based on some pretty clever mathematics: you could confidently calculate the impact probability for a freshly found asteroid over the next 100 years in under an hour – an astonishing achievement.”

On the other hand, Sentry-II gives NASA a tool that can quickly compute impact probability for all known NEAs, even some that the first Sentry missed. In the CNEOS Sentry Table, Sentry-II reports the most dangerous things.

Improved Monitoring System

The researchers have made the impact monitoring system more robust by routinely computing impact probabilities in this new approach, allowing NASA to accurately analyze all potential impacts with odds as low as a few chances in 10 million.

The asteroid’s dayside is heated by sunlight as it rotates. The hot surface will cool down when it turns to the asteroid’s shadowed nightside. As it cools, infrared energy is released, creating a small but constant force on the asteroid. The Yarkovsky effect is a phenomenon that has minimal impact on the asteroid’s speed over short periods of time but may drastically alter its course over decades and millennia.

Another flaw in the initial Sentry algorithm was that it couldn’t always forecast the impact probability of asteroids colliding with Earth at extremely close range. Our planet’s gravity deflects the velocity of these NEAs, increasing the post-encounter orbital uncertainty significantly. The original Sentry’s calculations may fail in some situations, necessitating manual intervention. Sentry-II is not limited in this way.

Tracking NEA

When telescopes track a new NEA, astronomers record the asteroid’s observed locations in the sky and submit them to the Minor Planet Center, which calculates impact probability. CNEOS then uses the information to calculate the asteroid’s most likely orbit around the Sun. However, because the asteroid’s measured location is subject to minor inaccuracies, its “best likely orbit” may not accurately reflect the asteroid’s actual orbit. The accurate orbit is located somewhere inside a rocky area, which resembles a cloud of possibilities encircling the most probable orbit.

The original Sentry would make certain assumptions about how the uncertainty zone would change to determine whether an impact is conceivable and narrow down where the genuine orbit might be. It would then choose a group of points that were uniformly spaced along a line that spanned the uncertainty zone. Each point reflected a probable current position of the asteroid that was somewhat different.

Comparing Sentry I and II


(Photo : Getty Images)

The Sentry would then advance the clock, keeping an eye on the “virtual asteroids” as they orbited the Sun to see if any came close to Earth in the future. If that’s the case, more computations would be needed to “zoom in” on whether any intermediate points may collide with Earth, and if so, what the impact probability would be.

Sentry-II, on the other hand, follows a different concept. The new method generates tens of thousands of random points without making assumptions about how the uncertainty zone will grow; instead, it picks random points from throughout the uncertainty region. Sentry-algorithm II then asks, “What are the probable orbits that may impact Earth inside the full zone of uncertainty?”

Also Read: How Ancient Asteroids and Comets Helped Alter Early Earth’s Oxygen Levels

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