Sentry (monitoring system)

Sentry is an automated impact prediction system started in 2002 and operated by the Center for Near Earth Object Studies (CNEOS) at NASA's Jet Propulsion Laboratory.

It continually monitors the most up-to-date asteroid catalog for possibilities of future impact with Earth over the next 100+ years.

[6] 2007 FT3 and 2014 MV67 with their very short 1-day observation arcs have missed virtual impactor dates as they were likely quite distant from the Earth at the time.

As of February 2025[update], of the 191 asteroids with better than a 1-in-10,000 chance of impacting Earth only (29075) 1950 DA, 101955 Bennu and 2024 YR4 are larger than 50 meters in diameter.

[8] It is estimated to be 55-meters in diameter, has an observation arc of 57-days, and is expected to be approximately 0.0023 AU (340 thousand km) from Earth on 22 December 2032 at the virtual impactor time of 14:02 UT.

In August 2013, the Sentry Risk Table started using planetary ephemeris (DE431) for all NEO orbit determinations.

JPL launched major changes to the website in February 2017 and re-directed the classic page on 10 April 2017.

In 2021 JPL launched Sentry-II which handles the Yarkovsky effect that can significantly change a small asteroid's path over decades and centuries.

Roughly 1400 of these risk-listed near-Earth asteroids are estimated to be about the size of the Chelyabinsk meteor or smaller (H>26), which killed no one but had 1,491 indirect injuries.

[15] The impact risk assessment is rated on a scale of 0–4 (negligible, small, modest, moderate, or elevated).