NASA Aims DART at a Double Asteroid Expecting A Cataclysmic Ending

NASA’s DART mission is heading to a double asteroid with the purposeful intent of crashing into it. Nothing on the spacecraft will survive, but the data it provides may help someday if another asteroid is on a collision course with Earth and must be diverted.

The Double Asteroid Redirection Test (DART) is part of NASA’s planetary defense program to determine ways to respond to the threat of an incoming asteroid or comet — Near Earth Objects (NEOs). The Planetary Defense Coordination Office (PDCO) has programs to find NEOs, warn other parts of the government if one is incoming, mitigate the threat by studying technologies and techniques to deflect one, and coordinate with other agenies on the National NEO Preparedness and Action Plan.

DART is part of the mitigation portfolio.

The golf-cart sized spacecraft is being sent to smash into a football-field sized asteroid, Dimorphos, that orbits a slightly larger asteroid, Didymos. The two are a “double asteroid” or binary system and Dimorphos is classified as a moon of Didymos.

The point of the mission is to determine how much the kinetic energy imparted by the collision changes the orbit of Dimorphos. If an asteroid was actually headed to Earth, such an impact could divert its trajectory. This is only a test. The Didymos/Dimorphos system is not headed towards Earth and poses no threat now or after the collision.

DART was built by the Johns Hopkins Applied Physics Lab (APL).  Ed Reynolds, APL’s project manager for DART, told reporters at a November 22 briefing they hope to change the period of Dimorphos’ orbit by 10 minutes. They’ll know if that happened through observations from Earth-based telescopes. DART also has a cubesat, LICIACube, aboard that will be ejected just prior to the collision to collect other data. LICIACube was provided by the Italian Space Agency.

A European Space Agency spacecraft, Hera, will also take a look when it flies past in 2026. DART and Hera are separate missions, but their investigations are coordinated through the Asteroid Impact and Deflection Assessment (AIDA) scientific consortium.

DART will arrive at its target between September 26 and October 1, 2022. Its APL-developed Small-body Maneuvering Autonomous Real Time Navigation (SMART Nav) system will aim to smack into Dimorphos dead-center, but little is actually known about the moon’s surface and composition so the exact outcome is difficult to predict.

Asked if they get a second chance if they miss the tiny 780-meter (2,500-foot) diameter moon on the first try, Reynolds said they are working “really hard not to miss” and “we’re not keeping a list of backup dual asteroids to retarget against,” but “the possibility is there.”  The spacecraft has not only small hydrazine thrusters to steer it towards its destiny, but an experimental ion propulsion system, NEXT-C (NASA’s Evolutionary Xenon Thruster-Commercial) developed by NASA’s Glenn Research Center and Aerojet Rocketdyne. Reynolds said NEXT-C has 50 kilograms of xenon and only 5 are needed for the tests that are planned, so there will be plenty left. A 2017 paper postulates alternatives if a second plan is needed.

A photo of DART encapsulated in its SpaceX Falcon 9 rocket fairing before launch illustrates how small it is by planetary mission standards, but as PDCO Director Lindley Johnson quipped, it is a “small but mighty spacecraft.”

The successful launch of the 610 kilogram (1,365 pound) spacecraft took place from Vandenberg Space Force Base, CA on November 23 at 10:21 pm Pacific Standard Time (1:21 am November 24 EST) on a SpaceX Falcon 9 rocket. The 10-month mission has a life-cycle cost of $330 million.

 

This article was updated.