NASA annually discovers over 3,000 asteroids; Here's how space agency tracks them all

An asteroid twice the size of the Empire State Building made its closest approach to Earth on January 18, making it the newest celestial body to skim past our planet this month. Dubbed 1994 PC1, this asteroid is about one kilometre wide and flew by at a staggering speed of 69,200 kilometres per hour from a safe distance of 1.93 million kilometres from Earth, as per NASA. This was the fifth asteroid that came close to our planet this month, adding to the list of space rocks that NASA identifies and warns us about. Among an uncountable number of such asteroids hurtling through the universe, keeping an eye on them must be rather hectic. NASA still does it anyway through software that runs on a special algorithm for tracking these lingering space bodies. 

Here’s how NASA keeps track of asteroids

The agency states that survey telescopes have discovered as many as 28,000 near-Earth asteroids (NEAs), as of now. This number, when broken down, equates to about 3,000 discoveries each year. Until now, NASA has kept an eye on each of its discoveries through the Center for Near-Earth Object Studies (CNEOS), which is managed by the Jet Propulsion Laboratory (JPL). According to the agency, astronomers have been able to track the asteroids through CNEOS which monitors the risk posed by the same through software called ‘Sentry’. Developed by JPL in 2002, the now-outdated Sentry was based on ‘smart mathematics’, which was capable of determining the impact probability for a newly discovered asteroid over the next 100 years. 

NASA upgrades to Sentry-II

Since Sentry became a technology of the past, NASA has now developed a newer and improved version of the software and has named it Sentry-II. The agency states that with the upgraded version, astronomers will be able to monitor asteroids and calculate their impact probabilities even of those special cases that were left out by Sentry. Interestingly, Sentry-II would allow the assessment of all potential impacts with odds as low as a few chances in 10 million. Another advantage offered by this newer technology is that it eliminates the drawbacks of its predecessor. 

Sentry’s limitation was that it was unable to assess the Yarkovsky effect, which is responsible for changing the path of an asteroid over decades or centuries. This effect is created when the sun rays heat one side of the asteroid and when the asteroid turns, its heated side cools down and releases infrared energy which produces a thrust to change the asteroid’s path. 

How does software work?

To understand the working of Sentry-II it is important to note that each asteroid has its uncertainty region which may evolve over time. According to NASA, what their new software algorithm does is that it selects random points throughout the entire uncertainty region and is not limited by any assumptions about how the uncertainty region may evolve. It then predicts the possible orbits within the entire region of uncertainty that could hit Earth thus allowing astronomers to zero in on more very low probability impact scenarios, which might have been missed by its predecessor.

(Image: NASA)