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NASA’s DART mission aims to save the world

Armageddon ruined everything. Armageddon— the 1998 movie, not the mythical Battlefield — told the story of an asteroid headed straight for Earth and a group of braggart thugs sent on space shuttles to blow it up with a nuclear weapon.

Armageddon It’s big and loud and stupid and shameless, and it’s going to be huge at the box office.” wrote Jay Carr of the boston globe.

Carr was right: the movie was the second biggest hit of the year (nah titanic), and ever since, scientists have had to patiently explain that saturating space with radioactive debris may not be the best way to protect ourselves. NASA is now testing a slightly less dramatic approach with a robotic mission called DART: Short for Double Asteroid Redirection Test. On Monday at 7:14 p.m. EDT, if all goes well, the little spacecraft will crash into an asteroid called dimorphic, about 11 million kilometers from Earth. Dimorphos is about 160 meters in diameter and orbits a 780 meter asteroid, 65803 Didymus. NASA TV plans cover it live.

The end of DART will be violent, but not violent like a blockbuster movie. The music won’t swell and the brides on Earth won’t swoon. Mission managers hope the spacecraft, with a mass of around 600kg, pounding at 22,000km per hour, will push the asteroid slightly into its orbit, enough to show that it is technologically possible should a future asteroid has Earth in its crosshairs.

“Maybe once every century or so, there will be an asteroid big enough that we’d like to know for sure, in advance, if it was going to hit,” he says. Lindley Johnsonwho has the title of Planetary Defense Officer in POT.

“If you just take a hair off the orbital velocity, you’ve changed the orbit of the asteroid, so that what would have been an impact three or four years from now is now a complete mistake.”

So take that, Hollywood! If DART is successful, it will prove that there are better fuels to protect the Earth than testosterone.

The risk of a comet or an asteroid wiping out civilization is actually very small, but big enough for politicians to take seriously. NASA, ordered by the United States Congress in 2005 to scan the inner solar system for dangers, has found almost 900 the so-called NEO—near earth objects—at least a kilometer wide, more than 95 percent of all in that size range likely to exist. It has plotted their orbits into the future, and none of them have more than a fraction of a percent chance of hitting Earth in this millennium.

The DART spacecraft should crash into the asteroid Dimorphos and slow down in its orbit around the larger asteroid Didymos. The LICIACube cubesat will fly in formation to obtain an image of the impact.Johns Hopkins APL/NASA

But there are smaller NEOs, perhaps 140 meters or more in diameter, too small to wipe out civilization but large enough to cause massive destruction if they hit a populated area. There may be 25,000 that are within 50 million kilometers of Earth’s orbit, and NASA estimates that telescopes have only found about 40 percent of them. That is why scientists want to expand the search for them and have good ways to deal with them if necessary. DART is the first test.

NASA is at pains to say that this is a low-risk mission. Didymos and Dimorphos never cross Earth’s orbit, and computer simulations show that no matter where or how hard DART hits, it can’t deflect either enough to put Earth in danger. Scientists want to see if DART can alter Dimorphos’ speed by perhaps a few centimeters per second.

The DART spacecraft, a one-meter cube with two long solar panels, is elegantly simple, equipped with a telescope called DRACO, hydrazine maneuvering thrusters, a xenon-powered ion engine, and a navigation system called SMART Navigation. what launched by a SpaceX rocket in November Approximately four hours and 90,000 km before the expected impact, SMART Nav will take control of the spacecraft, using optical images from the telescope. Didymus, the largest object, should be a point of light by then; Dimorphos, the intended target, probably won’t appear as more than one pixel until about 50 minutes before impact. DART will send one image per second to Earth, but the spacecraft is autonomous; signals from the ground, 38 light-seconds away, would be useless in orienting the ship as it moves forward.

A golden cubesat with a bright light and lines.The DART spacecraft separates from its SpaceX Falcon 9 launch vehicle 55 minutes after liftoff from Vandenberg Space Force Base, California, on November 24, 2021. In this image of the rocket, the spacecraft has not yet deployed its solar panels.POT

What’s more, no one knows the shape or consistency of little Dimorphos. Is it a solid rock or a loose clump of debris? Is it smooth or craggy, round or elongated? “We’re trying to get to the center,” he says. Evan SmithAssociate Mission Systems Engineer at the Johns Hopkins Applied Physics Laboratory, which runs DART. “We don’t want to over-correct for some mountain or crater on one side that casts a weird shadow or something.”

So, on final approach, DART will cover 800 km with no direction. Thruster firing could blur the latest images of Dimorphos’s surface, which scientists want to study. The impact is to be photographed from about 50 km away by an Italian-made mini-satellite, called LICIACubethat DART launched two weeks ago.

“In the minutes after impact, I know everyone will be giving engineering a high-five,” he said. tom statlerDART program scientist at NASA, “but I’m going to imagine all the cool things that are actually happening on the asteroid, with a crater dug out and ejecta ejected.”

Of course, there is a chance that DART might fail, in which case there should be enough fuel on board to allow engineers to pursue a backup target. But one advantage of the Didymos-Dimorphos pair is that it should help calculate how much effect the impact had. Telescopes on Earth (plus the Hubble and Webb Space Telescopes) may have difficulty measuring infinitesimal changes in Dimorphos’ orbit around the sun; it should be easier to see how much its orbit around Didymos is affected. The simplest measure may be the double asteroid’s change in brightness, as Dimorphos moves ahead or behind its companion, perhaps faster or slower than before impact.

“We’re moving an asteroid,” Statler said. “We are changing the movement of a natural celestial body in space. Humanity has never done that before.”

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