Celestial hazards: Twenty years of planetary defense

kilometers) of the Sun, and also within roughly 30 million miles (50 million kilometers) of Earth’s orbit around the Sun.

The media frenzy around NEO 1997 XF11 demonstrated the need for clarity and precision in communicating with the public about the close passes by Earth of these objects, as well as “the importance of peer review before public statements like these are made,” Chodas said.

JPL says that NASA’s original intent was to fulfill a 1998 Congressional request to detect and catalogue at least 90 percent of all NEOs larger than one kilometer in size (roughly two-thirds of a mile) within 10 years. To help reach the Congressional goal, NASA Headquarters requested that JPL establish a new office to work with the data provided by the International Astronomical Union-sanctioned Minor Planet Center for submission of all observations of asteroids and comets, and to coordinate with observatories operated by academic institutions around the United States, as well as U.S. Air Force space surveillance assets.

In the summer of 1998, NASA established the Near-Earth Object Observations Program and JPL became the home for the agency’s research data and analysis on NEOs, the “Near-Earth Object Program Office” (view the 1998 announcement here).

In 2016, the office was renamed the Center for Near-Earth Object Studies (CNEOS) in conjunction with the establishment of the Planetary Defense Coordination Office (PDCO) at NASA Headquarters in Washington.

For about 20 years, CNEOS has been NASA’s central hub for accurately mapping the orbits of all the known NEOs, predicting their upcoming close approaches, reliably assessing their chances of impact to our planet, and delivering that information to both astronomers worldwide and the general public.

Predicting close approaches and impacts: Sentry and scout
The first and most important step in assessing the impact risk of an asteroid or comet is to determine whether any given object’s orbit will cross Earth’s orbit — and then how close it will actually get to our planet. JPL was determining high-precision orbits for a few NEOs even before NASA launched its NEO Observations Program, and has since upgraded its orbit models to provide the most accurate assessment available for asteroid positions and orbits.