NASA to launch projectile (DART) to see if it can deflect asteroids

DART is a planetary defense-driven test of technologies for preventing an impact of Earth by a hazardous asteroid.  DART 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 for NASA’s Planetary Defense Coordination Office and the Science Mission Directorate’s Planetary Science Division at NASA Headquarters in Washington, DC.

DART Spacecraft Bus
Two different views of the DART spacecraft. The DRACO (Didymos Reconnaissance & Asteroid Camera for OpNav) imaging instrument is based on the LORRI high-resolution imager from New Horizons. The left view also shows the Radial Line Slot Array (RLSA) antenna with the ROSAs (Roll-Out Solar Arrays) rolled up. The view on the right shows a clearer view of the NEXT-C ion engine.

The binary near-Earth asteroid (65803) Didymos is the target for the DART demonstration. 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 Didymos binary is being intensely observed using telescopes on Earth to precisely measure its properties before DART arrives.

Didymos and its moonlet
Fourteen sequential Arecibo radar images of the near-Earth asteroid (65803) Didymos and its moonlet, taken on 23, 24 and 26 November 2003. NASA’s planetary radar capabilities enable scientists to resolve shape, concavities, and possible large boulders on the surfaces of these small worlds. Photometric lightcurve data indicated that Didymos is a binary system, and radar imagery distinctly shows the secondary body.
Didymos system
Simulated image of the Didymos system, derived from photometric lightcurve and radar data. The primary body is about 780 meters in diameter and the moonlet is approximately 160 meters in size. They are separated by just over a kilometer. The primary body rotates once every 2.26 hours while the tidally locked moonlet revolves about the primary once every 11.9 hours. Almost one sixth of the known near-Earth asteroid (NEA) population are binary or multiple-body systems.
Credits: Naidu et al., AIDA Workshop, 2016
DART spacecraft with the Roll Out Solar Arrays (rOSA)
Illustration of the DART spacecraft with the Roll Out Solar Arrays (ROSA) extended. Each of the two ROSA arrays in 8.6 meters by 2.3 meters.

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 DART 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.

the ROSA array on the ISS
The ROSA array was tested on board the International Space Station (ISS) in June 2017.

Once launched, DART will deploy Roll Out Solar Arrays (ROSA) to provide the solar power needed for DART’s electric propulsion system.  The DART 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.

The DART spacecraft launch window begins in late July 2021.  DART 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.

Source: Double Asteroid Redirection Test (DART) Mission | NASA