Hollywood films like Deep Impact and Armageddon were of course pure fiction. But the technology behind how NASA was able to detect any asteroid approaching earth’s orbit is real. NASA has had this detection capability since the early 2000’s and has improved on it considerably. The NASA asteroid spotting system and computer program is called Scout. Asteroids are no longer a concern for astronomers who will never be caught off guard ever again. For instance, just a few days ago, an asteroid passed by earth at a safe distance, but NASA was already aware of it when it was spotted days earlier and its flight path then calculated. Scout simply gathers data from major space telescopes around the world and sifts through it. When it spots anything heading towards earth, the computer program alerts its users who then begin calculating the NEO (Near Earth Object) flight path to determine how near it passes earth, or if there is a head-on collision possible.
According to NASA Jet Propulsion Laboratory (JPL) astronomer Paul Chodas in an interview with NPR, “At least 5 asteroids pass by near earth each day. The nearest ones usually pass at around 310,000 miles from the planet.” When a single telescope first finds a moving object, all that is seen is just a dot, moving in the sky. With no other information about how far away it is, so this is the reason why more telescopes pointing into space is needed, and in a way this is sort of like an international coalition of asteroid scouts because there are telescopes from diverse countries like Russia, India, Egypt, Japan, etc. This is good for the Scout because the more data that is provided, and the more NASA is sure just how big it is and which way the NEO is going.
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However, early warning time isn’t really that long. Scout can spot a coming asteroid if it is 5 days away. That gives the planet 5 days’ notice if any action needs to be taken. Realistically, that’s not much time except to pray and brace yourself in the hopes of the asteroid hitting the far side of the earth rather than yours. Scout can primarily focus on locating and identifying even small objects as small as between 5 meters and 25 meters in diameter. Scout actually has an older relative called Sentry. This is the original NASA and DoD detector system tasked with identifying asteroids that pose more serious threats to Earth. However, the drawback with the older Sentry system is that it can only identify 25-30 percent of asteroids starting at 140 meters in size. NASA is hoping that with the launching of the Large Synoptic Survey Telescope in Chile that comes online in the early 2020s, this will greatly improve both the Scout and Sentry systems. There are no plans to take Sentry offline or if Scout will eventually supersede its older relative.