With tonight’s launch, NASA starts getting serious about planetary defense

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Weather permitting, a Falcon 9 rocket will launch Tuesday night from California on a crucial asteroid-deflection mission for NASA. The Double Asteroid Redirection Test, or DART mission, next year will try to demonstrate its ability to alter the asteroid’s orbit.

Powered by ion thrusters, the 700-kilogram spacecraft is aiming to rendezvous with a double asteroid next October. Once there, the spacecraft will attempt to collide with Dimorphos, a small “moonlight” of a larger asteroid called Didymos. Dart will hit Dimorphos at a speed slightly over 6.6 km/s, aiming to slightly alter the trajectory of the asteroid, which is at a distance of about 170 metres.

If NASA successfully completes this test, it will, one day, have demonstrated its ability to deflect an oncoming asteroid on a collision course with Earth. “We’re trying to show that we can reduce this kind of threat,” said NASA science chief Thomas Zurbuchen in an interview with Ars.

planet defense

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Planetary Defense is the tracking and potential deflection of dangerous asteroids, comets and other large bodies that could collide with Earth. In public surveys, planetary defense has always ranked high among its options for what NASA should focus on, and the US Congress has asked the space agency to identify all asteroids 140 meters or more in diameter. It is an object large enough to destroy a city on Earth.

However, until about five years ago, NASA had made limited progress toward these goals. There were always big priorities for the space agency. And truth be told, the odds were in NASA’s favor. There are no known asteroids that threaten to strike Earth during the next century. And while rogue asteroids are possible, humanity could more than likely spend centuries waiting for the issue to be fully addressed. In all recorded history, there has, in fact, not yet been a human death that has been reliably attributed to an asteroid strike.

Major asteroid impacts are classic very low-probability, very high-consequence events. And yet doing nothing seems silly, especially because NASA can do something with a relatively small investment. So after becoming NASA’s associate administrator for the Science Mission Directorate in 2016, Zurbuchen tripled funding for planetary defense from $50 million to $150 million. This allowed NASA to fund not only research, but actual projects. Work soon began on the Dart mission, which is now ready to fly.

The next step, Zurbuchen said, is to fully fund the creation and assembly of the Near-Earth Object Surveyor mission, or NEO-Surveyor. This space-based observatory is designed to detect 65 percent of undiscovered asteroids 140 meters or larger within five years, and 90 percent of them within a decade.

The mission could begin by 2025, but it is subject to funding from Congress. The White House has asked for funding in the fiscal year 2022 budget to begin construction of the NEO Surveyor.

more to do

“I believe we have a planetary defense program that’s worth talking about right now,” Zurbuchen said. “I’m really proud of what we’ve been able to do. But I still believe we can do better.”

If Dart is successful, Zurbuchen said, a possible next step is to develop a fully-fueled kinetic impactor that can be pre-installed in Earth orbit. Such a capability, he said, would be ready to go if an asteroid is found to be on an intercept course with Earth. The farther an asteroid can be deflected, the more meaningful the deflection will be.

A small spacecraft (DART) inside a large fairing (Falcon 9).
NASA/Johns Hopkins APL/Ed Whitman

The first stage of the Falcon 9, which launched the Dart mission, has flown two previous missions: the Sentinel-6 mission for NASA in November 2020, and the SpaceX Starlink mission in May 2021. Liftoff is scheduled for 10:20 a.m. local time from Vandenberg Space Force Base. in California (1:20 AM EST Wednesday, 06:20 UTC Wednesday).

The weather appears to be favorable for launch, with a 90 percent chance of “go” conditions. SpaceX has already conducted a steady-fire test of the rocket and has not reported any issues that would prevent a timely launch.

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