After ten months in space, NASA’s Double Asteroid Redirection Test(DART) – the world’s first planetary defence technology demonstration – successfully impacted its asteroid target on September 26, 2022, Monday. It was NASA’s first attempt to deflect the asteroid’s orbit.
An Analysis of data obtained over the past two weeks by NASA’s DART investigation team shows the spacecraft’s kinetic impact with Dimorphos successfully altered the asteroid’s orbit. This marks humanity’s first time purposely changing the motion of a celestial object and the first full-scale demonstration of asteroid deflection technology, NASA said.
“All of us have a responsibility to protect our home planet. After all, it’s the only one we have,” said NASA Administrator Bill Nelson. “This mission shows that NASA is trying to be ready for whatever the universe throws at us. NASA has proven we are serious as a defender of the planet. This is a watershed moment for planetary defence and all of humanity, demonstrating commitment from NASA’s exceptional team and partners from around the world.”
“This result is one important step toward understanding the full effect of DART’s impact with its target asteroid” said Lori Glaze, director of NASA’s Planetary Science Division at NASA Headquarters in Washington. “As new data come in each day, astronomers will be able to better assess whether, and how, a mission like DART could be used in the future to help protect Earth from a collision with an asteroid if we ever discover one headed our way.”
The investigation team is still acquiring data with ground-based observatories around the world – as well as with radar facilities at NASA Jet Propulsion Laboratory’s Goldstone planetary radar in California and the National Science Foundation’s Green Bank Observatory in West Virginia. They are updating the period measurement with frequent observations to improve its precision.
Focus now is shifting toward measuring the efficiency of momentum transfer from DART’s roughly 14,000-mile (22,530-kilometre) per hour collision with its target. This includes further analysis of the “ejecta” – the many tons of asteroidal rock displaced and launched into space by the impact. The recoil from this blast of debris substantially enhanced DART’s push against Dimorphos – a little like a jet of air streaming out of a balloon sends the balloon in the opposite direction.
However, the success of the impact will take a few weeks more to know.
NASA Administrator Bill Nelson said “at its core, DART represents an unprecedented success for planetary defence, but it is also a mission of unity with a real benefit for all humanity. As NASA studies the cosmos and our home planet, we’re also working to protect that home, and this international collaboration turned science fiction into science fact, demonstrating one way to protect Earth.”
NASA’s Planetary Defence OfficerLindley Johnson opined that DART’s success provided a significant addition to the essential toolbox that the world must have to protect from a devastating impact by an asteroid. “This demonstrates we are no longer powerless to prevent this type of natural disaster. Coupled with enhanced capabilities to accelerate finding the remaining hazardous asteroid population by our next Planetary Defence mission, the Near-Earth Object (NEO) Surveyor, a DART successor could provide what we need to save the day,” Johnson said.
The DART mission is NASA’s demonstration of kinetic impactor technology, impacting an asteroid to adjust its speed and path. DART will be the first-ever space mission to demonstrate asteroid deflection by kinetic impactor.
The spacecraft launched on a SpaceX Falcon 9 rocket out of Vandenberg Space Force Base in California.
DART will navigate to crash itself into Dimorphos at a speed of approximately 6.1 kilometres (3.8 miles) per second. The total mass of the DART spacecraft was approximately 1,345 pounds (610 kilograms) at launch and will be roughly 1260 pounds (570 kilograms) at impact. DART carries both hydrazine propellant (about 110 pounds, or 50 kilograms) for spacecraft manoeuvres and attitude control, and xenon (about 130 pounds, or 60 kilograms) to operate the ion propulsion technology demonstration engine.
DART’s target was the binary asteroid system Didymos. Didymos is the ideal candidate for humankind’s first planetary defence experiment, although it is not on a path to collide with Earth and therefore poses no actual threat to the planet. The system is composed of two asteroids: the larger asteroid Didymos (diameter: 780 meters, 0.48 miles), and the smaller moonlet asteroid, Dimorphos (diameter: 160 meters, 525 feet), which orbits the larger asteroid. Currently, the orbital period of Dimorphos around Didymos is 11 hours and 55 minutes, and the separation between the centres of the two asteroids is 1.18 kilometres (0.73 miles). The DART spacecraft will impact Dimorphos nearly head-on, shortening the time it takes the small asteroid moonlet to orbit Didymos by several minutes.
The timing of the DART impact in September 2022 was chosen to be when the distance between Earth and Didymos is minimized, to enable the highest quality telescopic observations. Didymos will still be roughly 11 million kilometres (7 million miles) from Earth at the time of the DART impact,
The DART payload consisted of a single instrument, the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO). DRACO is a high-resolution imager derived from the New Horizons LORRI camera to support navigation and targeting, to measure the size and shape of the asteroid target, and to determine the impact site and geologic context. DRACO is a narrow-angle telescope with a 208-millimetre aperture and field of view of 0.29 degrees.
DART also carried a CubeSat contributed by Agenzia Spaziale Italiana (ASI), named LICIACube (Light Italian CubeSat for Imaging of Asteroids).
LICIACube will capture images of the DART impact, the resulting ejecta cloud, and potentially a glimpse of the impact crater on the surface of Dimorphos. The design of the LICIACube spacecraft is based on a 6U platform developed by the aerospace company Argotec. LICIACube has two instruments: LEIA (LICIACube Explorer Imaging for Asteroid), a narrow field panchromatic camera to acquire images from long distance with a high spatial resolution and LUKE (LICIACube Unit Key Explorer), a wide field RGB camera, allowing a multicolour analysis of the asteroidal environment.