NASA’s Double Asteroid Redirection Test (DART) mission, will test a method of deflecting an asteroid for planetary defense, using the “kinetic impactor” technique.
DART mission key facts
– Launched: Nov. 24, 2021 at 1:20 a.m. EDT (0620 GMT)
– Launch site: Space Launch Complex 4, Vandenberg Space Force Base in California
– Rocket: SpaceX Falcon 9
– Target: Didymos and its moonlet Dimorphos.
– Target distance from Earth: 6.8 million miles (11 million kilometers)
– Estimated cost: $313.9 million (£227.9 million)
– DART impact: Sept. 26, 2022.
DART will slam into a small asteroid — Dimorphos — in a bid to change the moonlet’s orbital speed by a fraction of a percent according to NASA (opens in new tab). Though Dimorphos poses no threat to Earth, the ambitious mission mimics what NASA scientists would do if an asteroid were headed toward Earth.
Daisy joined Space.com as a reference writer in February 2022, before then she was a staff writer for our sister publication All About Space magazine.
The DART mission was launched at 10:20 p.m. local time on Nov. 23, 2021, (1:20 a.m. EDT, or 0620 GMT Nov. 24) atop a SpaceX Falcon 9 rocket from the Space Launch Complex 4 at the Vandenberg Space Force Base in California.
The mission demonstrates the high level of international collaboration that is needed for such an ambitious mission. Though the DART mission is managed by the John Hopkins University Applied Physics Laboratory (opens in new tab) (JHUAPL), scientists and engineers from around the world have come together to contribute.
“We’ve worked really closely with our European colleagues and colleagues all over the world,” Ellen Howell, a senior research scientist at the University of Arizona Lunar and Planetary Laboratory and a co-investigator for DART, told Space.com. Though DART is a test, a similar level of international cooperation would be essential in the case of a real impact, she said.
Why is the DART mission important?
Though the threat from asteroid impacts is small, it is a threat nonetheless, and something we should be prepared for. We only need to look at past impact events such as the massive Chicxulub asteroid impact that is credited with the extinction of the dinosaurs 65 million years ago, to see the catastrophic effects an impact can have on life on Earth.
Early detection of near-Earth asteroids is the first step in planetary defense. Approximately 30 new discoveries of near-Earth asteroids (opens in new tab) are made each week and at the start of 2019, there were more than 19,000 discovered near-Earth asteroids according to NASA. DART will be the first mission to test an asteroid deflection technique.
DART mission target
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The mission’s target is the binary asteroid system Didymos, which means “twin” in Greek. The system consists of a near-Earth asteroid Didymos measuring 0.48 miles (780 meters) across and its moonlet Dimorphos measuring 525 feet (160 meters) across.
DART will deliberately impact the moonlet Dimorphos at speeds of 4.1 miles per second (6.6 km/s). That’s an eye-popping 14,760 mph (23,760 kph). The impact should cause the moonlet’s orbital speed to change by a fraction of a percent and this shift should be enough to change its orbital period by several minutes. According to NASA, the change in Dimorphos’ orbit around Didymos will be observed and measured by telescopes on Earth, to see whether the mission has succeeded.
Though the pair are not a threat to Earth, they are perfect candidates for the DART mission as Dimorphos is around the same size as an asteroid that could pose the most likely threat to Earth (if one were on a collision course with the planet) according to NASA. Their orbit around the sun is also close enough to Earth for ground-based telescopes to observe and measure any differences after the collision.
Planetary scientist Nancy Chabot from JHUAPL spoke about the mission strategy with Space.com’s sister publication How It Works magazine.
Nancy Chabot is a planetary scientist at the Johns Hopkins Applied Physics Laboratory (APL) and serves as a project scientist on the Double Asteroid Redirection Test (DART) mission.
“One of the major technology challenges of the mission is targeting a small asteroid in space at very high speed when that asteroid has never been imaged by spacecraft previously”, Chabot said.
“We know from other asteroids that have been explored that they have a range of shapes, internal structures, surface properties and strengths, and these characteristics will influence how much the asteroid Dimorphos is deflected in its orbit around Didymos.”
What will DART do?
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DART is a simple spacecraft. According to JHUAPL, the box-shaped main vehicle (opens in new tab) measures roughly 3.9 x 4.3 x 4.3 feet (1.2 x 1.3 x 1.3 meters) — about the size of a refrigerator. Each of the two large solar arrays is 27.9 feet (8.5 meters) long when fully deployed. The DART spacecraft contains just one instrument — Didymos Reconnaissance and Asteroid Camera for Optical Navigation (DRACO). (It turns out that if your primary goal is to smash into an asteroid, you don’t need to take a lot with you).
Once the DART spacecraft launches on its SpaceX Falcon 9, it will deploy its Roll-Out Solar Arrays (ROSA) to power itself for the journey to Didymos. Scientists tested the ROSA arrays onboard the International Space Station in June 2017 and were deemed suitable to provide the power required to support DART’s electric propulsion system, according to NASA. (In fact, NASA has added larger versions of the ROSA arrays to the space station’s power grid.) The DART spacecraft will also use the next-generation, fuel-efficient NASA Evolutional Xenon Thruster-Commercial (NEXT-C) solar electric propulsion system as part of its in-space propulsion.
According to JHUAPL, DART will be guided to its target Dimorphos by sophisticated autonomous navigation software (opens in new tab). It’s no easy feat to locate a target that is 525 feet (160 meters) in diameter and 6.8 million miles (11 million kilometers) away from Earth. According to JHUAPL, the navigation software is designed to identify both Didymos and Dimorphos and distinguish between the two, so the DART spacecraft can be directed to the smaller body — Dimorphos.
As the spacecraft approaches its target, an onboard high-resolution camera — DRACO will help navigate the DART spacecraft and take measurements of the target asteroid, including the size and shape of Dimorphos. DRACO is based on the LORRI camera from NASA’s New Horizons spacecraft.
DART’s companion: LICIACube
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According to NASA, the DART spacecraft isn’t making its journey to the near-Earth asteroid binary alone, as the spacecraft is joined by LICIACube (opens in new tab) (Light Italian Cubesat for Imaging Asteroids). LICIACube is a cubesat contributed by the Italian Space Agency and built by Italian aerospace engineering company Argotec (opens in new tab).
The small cubesat weighs just 31 pounds (14 kilograms) and measures roughly the length of an adult’s hand and forearm. It is fitted with two optical cameras and will follow DART towards Dimorphos before settling in to watch the collision from a safe distance — of about 600 miles (1,000 km).
The role of LICIACube is to carefully observe the impact to help confirm whether the experiment has worked.
“LICIACube will … perform a ‘fast fly-by’ around 3 minutes after DART impact at a minimum distance of about 55 km [34 miles] from Dimorphos’ surface at its closest approach,” Mazzotta Epifani, an astronomer at Italy’s National Institute for Astrophysics (INAF) and a co-investigator on the LICIACube mission, told Space.com in an email.
“The image acquisition by the two cameras onboard will be almost continuous for around 10 minutes and will be devoted to the target impact and non-impact sides, as well as to the plume produced by the DART impact.”
LICIACube will then send the images to Earth, but Mazzotta Epifani warned it might take weeks to get down all the data.
What happens after impact?
After DART’s impact with Dimorphos, ESA’s Hera mission will conduct post-impact investigations according to JHUAPL. The spacecraft is planned to launch in October 2024, according to the mission website (opens in new tab) and reach the Didymos binary system in December 2026.
ESA’s Hera spacecraft will be joined by two cubesats. Together, they will carry out surveys of both Didymos and Dimorphos, paying particular attention to the crater left by DART’s collision with Dimorphos. The Hera mission also aims to determine a precise mass of Dimosphos, according to JHUAPL.
Though the two missions, DART and Hera are designed and operated independently, together they will advance our understanding of planetary defense technologies. Team members from both missions are part of an international collaboration known as AIDA — Asteroid Impact and Deflection Assessment. According to ESA, AIDA is a large international collaboration (opens in new tab) between ESA, the German Aerospace Center (DLR), Observatoire de la Côte d´Azur (OCA), NASA, and the John Hopkins University Applied Physics Laboratory (JHUAPL).
DART is just one part of a larger planetary defense strategy that is led by NASA’s Planetary Defence Coordination Office, according to Chabot.
“DART’s demonstration of this technology will be a major result to inform future planetary defense activities”, she said.
“Finding, tracking and characterizing the near-Earth object population is crucially important to the success of any future planetary defense mitigation efforts, of which DART is just the first test.”
–”DART delayed to November launch as environmental testing begins (opens in new tab)“. NASA Spaceflight (2021).
–”DART, NASA’s test to stop an asteroid from hitting Earth (opens in new tab)“. The Planetary Society (2022).
–”DART Updates (opens in new tab)“. NASA (2022).
–”DART: Double Asteroid Redirection Test (opens in new tab)“. John Hopkins University Applied Physics Laboratory: DART (2022).
–”DART Impactor (opens in new tab)“. John Hopkins University Applied Physics Laboratory: DART (2022).