NASA's first planetary defense spacecraft, the DART asteroid mission

The Double Asteroid Redirection Test mission, or DART for short, is a large-scale NASA initiative that aims to evaluate a "kinetic impactor" technology for deflecting asteroids for planetary defense. On Nov. 23, 2021, at 10:20 p.m. local time (1:20 a.m. EDT, or 6:20 a.m. GMT, Nov. 24, a SpaceX Falcon 9 rocket was used to launch the DART mission from Space Launch Complex 4 at the Vandenberg Space Force Base in California. In late September 2022, the spacecraft is expected to reach its destination, according to NASA officials. A binary asteroid (65803) Didymos and its small moon Dimorphos are the targets of DART. The Planetary Society claims that the DART mission is the first planetary defense mission to test asteroid deflection techniques.

DART will intentionally strike the moonlet Dimorphos at a speed of 4.1 mph (6.6 km/h). That is a staggering 14,760 mph (23,760 kph). According to NASA, the impact should alter the moonlet's orbital speed by a tiny percentage. Its orbital period should alter by several minutes as a result of this small adjustment. In order to determine if the mission was successful, observatories on Earth will monitor and measure the change in Dimorphos' orbit around Didymos.

DART mission target

Graphic showing the path of DART towards Dimorphos. (Image credit: NASA/Johns Hopkins APL)

The Planetary Society claims that even if the threat from asteroid impacts is minimal, we should be ready in case one does occur. To understand the disastrous impacts an impact may have on life on Earth, we simply need to consider prior impact events like the enormous Chicxulub asteroid impact, which is blamed for the extinction of the dinosaurs 65 million years ago. The first stage in planetary defense is the early detection of near-Earth asteroids. According to NASA, there were more than 19,000 newly detected near-Earth asteroids at the beginning of 2019; on average, 30 new near-Earth asteroids are discovered each week(opens in new tab). The first mission to test an asteroid deflection method will be DART.

The John Hopkins University Applied Physics Laboratory is in charge of NASA's DART mission(opens in new tab) (JHUAPL). Didymos, which is Greek for "twin," is the name of the binary asteroid system that the expedition is aiming for. A near-Earth asteroid (65803) that is 0.48 miles (780 meters) across and its moonlet Dimorphos, which is 525 feet (160 meters) across, make up the system. Despite the fact that neither object poses a threat to Earth, Dimorphos is a great candidate for the DART mission because, according to NASA, it is about the same size as an asteroid that would be the most likely to do so if it were on a crash path with the planet. Additionally, due to their close proximity to Earth in their orbits around the sun, ground-based observatories may detect and analyze any variations that result from the impact. Nancy Chabot, a planetary scientist from JHUAPL, discussed the mission plan.

A fundamental technological hurdle of the project, according to Chabot, is the need to target a small asteroid in orbit at a fast rate of speed when it has never been observed by a spacecraft before. These features will affect how much the asteroid Dimorphos is deflected in its orbit around Didymos. We know that asteroids have a variety of forms, interior structures, surface properties, and strengths.

DART mission operations

Illustration showing the size comparison between DART, Didymos and Dimorphos. DART site between a bus and the Arc De Triomphe in terms of size. Dimorphos is located between the Statue of Liberty and the Great Pyramid of Giza. While Didymos is between the One World Trade Center and Burj Khalifa (Image credit: NASA/Johns Hopkins APL)

A basic spacecraft is DART. The primary vehicle's dimensions are around 3.9 x 4.3 x 4.3 feet (1.2 x 1.3 x 1.3 meters), or about the size of a refrigerator, according to JHUAPL. When fully extended, each of the two substantial solar arrays is 27.9 feet (8.5 meters) in length. One instrument, the Didymos Reconnaissance and Asteroid Camera for Optical Navigation is all that the DART spacecraft is equipped with (DRACO). It turns out that you don't need to bring anything with you if your main objective is to collide with an asteroid.

The DART spacecraft will deploy its Roll-Out Solar Arrays (ROSA) to power itself for the trip to Didymos once it lifts off on its SpaceX Falcon 9. According to NASA, the ROSA arrays(opens in new tab) were put to the test by scientists in June 2017 on the International Space Station and were found to be capable of supplying the necessary power to sustain DART's electric propulsion system. (NASA actually expanded the ROSA arrays(opens in new tab) to power the space station's own grid.) As part of its in-space propulsion, the DART spacecraft will also employ the next-generation, fuel-efficient NASA Evolutional Xenon Thruster-Commercial (NEXT-C) solar electric propulsion system.

According to JHUAPL, advanced autonomous navigation software will direct DART to its target Dimorphos (opens in new tab). Finding a target that is 525 feet (160 meters) in diameter, 6.8 million miles (11 million kilometers) from Earth, is no small task. JHUAPL claims that in order to send the DART spacecraft to the smaller body Dimorphos, the navigation software is built to recognize and discriminate between Didymos and Dimorphos.

DART's onboard high-resolution camera DRACO will assist in spacecraft navigation as it gets closer to its target while taking measurements of the asteroid, including Dimorphos' size and form. The LORRI camera from NASA's New Horizons(opens in new tab) mission served as the inspiration for DRACO.

DART Companion LICIACube 

A person wearing white is holding the top of LICIACube whilst wearing laboratory gloves.  (Image credit: NASA/Johns Hopkins APL/Ed Whitman)

The DART spacecraft will not be traveling to the near-Earth asteroid binary alone, according to NASA; it will be accompanied by LICIACube (opens in new tab) (Light Italian Cubesat for Imaging Asteroids). The Italian Space Agency and Italian aerospace engineering firm Argotec collaborated on the construction of LICIACube, a CubeSat.

The LICIRACube, according to NASA, weighs about 14 kilograms (31 pounds) and is about the length of an adult's hand and forearm. Around 10 days before the spacecraft would strike Dimosphos, DART will deploy the little CubeSat, which has a very vital mission. Then, according to Argotec, LICIACube will stand back and observe the collision, taking pictures of it to assist confirm its effectiveness.

Post impact investigations: HERA mission

According to JHUAPL, the ESA's Hera mission will examine the impact of DART with Dimorphos after it has occurred. It is anticipated that the spacecraft will launch in 2024 and arrive at the Didymos binary system in 2026. Two CubeSats will join the ESA's Hera mission in orbit. Both Didymos and Dimorphos will be surveyed by the two of them, with special attention paid to the crater caused by DART's crash with Dimorphos. According to JHUAPL, the Hera mission also seeks to establish the precise mass of Dimosphos.

According to her, the technology's demonstration by DART will have a significant impact on how planetary defense efforts are planned in the future. The effectiveness of any future planetary defense mitigation initiatives, of which DART is only the first test, depends critically on finding, tracking, and characterizing the population of near-Earth objects.

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