20 years tracking objects close to the Earth | Space

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The NASA Jet Propulsion Laboratory published this story

On March 11, 1998, asteroid astronomers around the world received a disturbing message: new observational data on the asteroid 1997 XF11 was a chance that the object half a mile wide (nearly a kilometer wide) reached the Earth in 2028.

The message came from the Minor Planet Center, in Cambridge, Massachusetts, the global repository for these observations and the initial determination of orbits of asteroids. And although it was intended to alert only the very small astronomical community that hunts and tracks asteroids to claim more observations, the news quickly spread.

Most media did not know what to do with the announcement. that the Earth was doomed.

Fortunately, it turned out that the Earth was never in danger from 1997 XF11. After conducting a more in-depth analysis of the orbit with available asteroid observations, Don Yeomans, then head of the Solar System Dynamics group at NASA's Jet Propulsion Laboratory in Pasadena, California, with his colleague Paul Chodas , concluded otherwise. Chodas, who is now director of NASA's Near-Earth Object Studies Center (NESO), located at JPL, said:

The impact of 2028 was essentially impossible.

To date, we still have questions about the chances of XF11 impacted in 2028. There is no chance that XF11 is affecting our planet this year, or for the next 200 years.

Chodas knows this through accurate orbit calculations of CNEOS using observational data submitted to the Minor Planet Center by observatories all over the world that detect and track the movement of asteroids and comets. Over the last two decades, CNEOS calculations have allowed NASA to become the world leader in these efforts, closely monitoring all nearby asteroids and comets – particularly those that can cross the Earth's orbit. Chodas said:

We calculate high precision orbits for all asteroids and comets and map their positions in the solar system, both to detect potential impacts and back to see where they have been in the sky . We provide the best orbital map for all known small bodies in the solar system.

Cartography of the Celestial Danger

Near-Earth Objects (NEO) are asteroids and comets in orbit that bring them into the inner solar system, within 121 million miles (195 million km) of the sun, and also in about 30 million miles (50 million km) of Earth's orbit around the sun.

The media frenzy around NEO 1997 XF11 demonstrated the need for clarity and accuracy in communicating with the public Chodas said:

… the importance of peer review before public statements such as these are made.

The original intent of NASA was to complete a 1998 congressional application to detect and index at least 90% of all NEOs by more than one kilometer (about two-thirds of a mile). Here 10 years. To help achieve the Congress goal, the NASA headquarters requested that the JPL establish a new office to work with the data provided by the Planet Minor Center approved by the International Astronomical Union for the submission of all observations of asteroids and comets. (19659005) In the summer of 1998, NASA established the NEO Observer Program, and JPL hosted the agency's research and analysis data on the objects. Next, it was renamed Center for Near-Earth Objects Studies (CNEOS) in 2016, along with the creation of the Planetary Defense Coordination Office at NASA headquarters in Washington

. ] For about 20 years, CNEOS has been the nerve center of NASA for accurately mapping the orbits of all known executives in anticipation of their next pain close, reliably assessing their chances of impact. on our planet, and transmitting this information to astronomers around the world and to the general public.

Predicting Close Approaches and Impacts: Sentinel and Scout

The First and Most An Important Step in Assessing the Risk of an Asteroid's Impact or of a comet is to determine if the orbit of a given object will cross the orbit of the Earth – and then how well it will actually reach our planet. The JPL was in the process of determining high-precision orbits for some near-Earth objects even before NASA launched its NEO observation program and has since upgraded its orbital models to provide the most accurate assessment possible of the NEOs. Asteroids' positions and orbits

from the sky to detect the moving points of light (the asteroid or the comet) over days, weeks, months and even decades. They then report the positions of these moving objects in relation to the static background of the stars in the center of the minor planet (for more details, see How a Light Point Becomes an Asteroid). CNEOS scientists then use all of these observational data to more accurately calculate the NEO's orbit and predict their movement over time for many years, looking for near approaches and potential impacts on the Earth, its moon and other planets. The system called Sentry is looking for all future possibilities of impact on the Earth over the next 100 years – for every known NEO. Sentry's impact monitoring works continuously using the latest orbital models generated by CNEOS, and the results are stored online. In most cases up to now, the probabilities of any potential impact are extremely low and in other cases, the objects themselves are so small – less than 20 meters, or nearly 66 feet – that they would almost disintegrate into the atmosphere of the Earth. Steve Chesley of JPL, a member of the CNEOS team who was the lead developer of the Sentry system, said:

If Sentry finds potential impacts on an object, we add it to our online table on the risk of impact and to the observers of asteroids can then give priority to this object for later observation. The more we measure the position of the object in time, the better we can predict its future trajectory

In most cases, the new measurements mean that the object can be removed from the risk list because that the uncertainties on the orbital path are reduced. the possibility of impact is discarded.

More recently, CNEOS has also developed a system called Scout to provide more immediate and automatic trajectory analyzes for the most recently discovered objects, even before independent observatories confirm their discovery. Operating 24 hours a day, the Scout system not only alerts observers of the highest priority objects to be observed at all times, but also immediately alerts the Global Defense Coordination Office of any imminent impacts in the following hours or days . the impact of the small asteroid 2018 LA on Botswana, Africa

More hunting to do

With the addition of studies on asteroids funded by the NASA, NASA's Observations by NEO The program is responsible for more than 90% of the asteroid and terrestrial comet discoveries. There are now more than 18,000 known NEOs and the discovery rate is on average about 40 per week.

Although the initial goal of the 1998 Congress has been surpassed and much progress has been made in the discovery and tracking of asteroids over the last two decades. In 2005, Congress set a much more ambitious new goal for the NEO Observer Program: discovering 90% of NEOs up to a much smaller size of 450 feet (140 meters), and this By 2020. [19659005] These smaller asteroids may not represent a global disaster threat if they affect the Earth, but they could nonetheless cause massive regional devastation and loss of life, particularly 39 They occur near a metropolitan area. CNEOS continues to improve its orbital analysis tools, graphical and graphical presentation capabilities and updates to its websites to provide the latest information on near-Earth objects at PDCO to the community in a timely and accurate manner. astronomical and to the public.

More information on CNEOS, asteroids and near-Earth objects can be found at:

https://cneos.jpl.nasa.gov

https: //www.jpl .nasa.gov/asteroidwatch

For more information on NASA's Global Defense Coordination Office, visit:

https://www.nasa.gov/planetarydefense

For news and updates on asteroids and comets, follow @AsteroidWatch on Twitter.

Via NASA / JPL-Caltech