What should we do if we find a dangerous asteroid on course to hit Earth?
There are a number of possible deflection techniques, ranging from extreme (a nuclear blast) to benign (a heavy spacecraft uses gravity to nudge the asteroid off-course).
Somewhere in between is the kinetic impactor technique. The concept is simple: Slam one or more spacecraft into the asteroid at high speed to change its orbit and move Earth out of the crosshairs.
This technique works particularly well if used far in advance since small nudges can add up to big changes later on.
And this is where DART, NASA’s Double Asteroid Redirection Test comes into play.
DART is a planetary defense-driven test of technologies for preventing an impact on Earth by a hazardous asteroid.
It will be the first demonstration of the kinetic impactor technique to change the motion of an asteroid in space.
The DART mission is in Phase C, led by APL and managed under NASA’s Solar System Exploration Program at Marshall Space Flight Center.
The DART launch window begins November 24, 2021.
The spacecraft will launch aboard a SpaceX Falcon 9 rocket from Vandenberg Air Force Base, California.
After separation from the launch vehicle and over a year of cruise, it will intercept Didymos’ moonlet in late September 2022, when the Didymos system is within 11 million kilometers of Earth, enabling observations by ground-based telescopes and planetary radar to measure the change in momentum imparted to the moonlet.
The binary near-Earth asteroid (65803) Didymos is the target for the DART demonstration.
The Didymos system is an eclipsing binary as viewed from Earth, meaning that Dimorphos passes in front of and behind Didymos as it orbits the larger asteroid as seen from Earth.
Consequently, Earth-based telescopes can measure the regular variation in brightness of the combined Didymos system to determine the orbit of Dimorphous.
After the impact, this same technique will reveal the change in the orbit of Dimoprhos by comparison to measurements prior to impact.
The timing of the DART impact in fall 2022 is chosen to minimize the distance between Earth and Didymos to enable the highest quality telescopic observations.
Didymos will still be roughly 11 million kilometers (6.8 million miles) from Earth at the time of the DART impact, but telescopes across the world will be able to contribute to the global international observing campaign to determine the effect of DART's impact.
The DART demonstration has been carefully designed.
The impulse of energy that DART delivers to the Didymos binary asteroid system is low and cannot disrupt the asteroid, and Didymos's orbit does not intersect Earth's at any point in current predictions.
Furthermore, the change in Dimorphos's orbit is designed to bring its orbit closer to Didymos.
The DART mission is a demonstration of capability to respond to a potential asteroid impact threat, should one ever be discovered.
While the Didymos primary body is approximately 780 meters across, its secondary body (or “moonlet”) is about 160-meters in size, which is more typical of the size of asteroids that could pose the most likely significant threat to Earth.
The DART spacecraft will achieve the kinetic impact deflection by deliberately crashing itself into the moonlet at a speed of approximately 6.6 km/s, with the aid of an onboard camera (named DRACO) and sophisticated autonomous navigation software.
The collision will change the speed of the moonlet in its orbit around the main body by a fraction of one percent, but this will change the orbital period of the moonlet by several minutes - enough to be observed and measured using telescopes on Earth.
Once launched, DART will deploy Roll-Out Solar Arrays (ROSA) to provide the solar power needed for DART’s electric propulsion system.
The spacecraft will demonstrate the NASA Evolutionary Xenon Thruster – Commercial (NEXT-C)solar electric propulsion system as part of its in-space propulsion.
NEXT-C is a next-generation system based on the Dawn spacecraft propulsion system and was developed at NASA’s Glenn Research Center in Cleveland, Ohio.
By utilizing electric propulsion, DART could benefit from significant flexibility to the mission timeline while demonstrating the next generation of ion engine technology, with applications to potential future NASA missions.
ESA’s Hera and NASA’s AIDA International Collaboration -
The Hera mission, a program in the European Space Agency's (ESA) space safety and security activities, is planned to launch in 2024 and rendezvous with the Didymos system in 2026, roughly four years after DART's impact.
During Hera's mission, the main spacecraft and its two companion CubeSats will conduct detailed surveys of both asteroids, with particular focus o n the crater left by DART's collision and a precise determination of the mass of Dimorphos.
Both DART and Hera team members are part of the largely international collaboration known as AIDA—Asteroid Impact and Deflection Assessment.
AIDA is the international collaboration among planetary defense and asteroid science researchers that will combine the data obtained from NASA's DART mission, which includes ASI's LICIACube, and ESA's Hera mission to produce the most accurate knowledge possible from the first demonstration of an asteroid deflection technology.
AIDA is the combined effort of the DART, LICIACube, and Hera teams, along with other researchers worldwide, to extract the best possible information for planetary defense and Solar System science from these groundbreaking space missions.
Next up on DiscoverZen, we will be discussing “How SpaceX Starship is the Key to Success of NASA's Artemis Mission?”.
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