By Jon Reino
NASA's mission to impact an asteroid has launched from Vandenberg Space Force Base in Lompoc, CA. Here is everything you need to know about this ambitious mission to avert a potential Armageddon.
Liftoff of 'DART' (Photo: NASA/Bill Ingalls)
On November 23rd at 10:21 PM local Pacific Time (11/24/21 6:21 UTC), the 'Double Asteroid Redirection Test' launched atop a SpaceX Falcon 9 rocket. Its destination is known as "Didymos", a binary asteroid system containing a large asteroid half a mile across and a smaller secondary body about 530 ft across called "Dimorphos". The two objects are locked in a gravitational dance, providing NASA with a unique opportunity to study the effects of a kinetic impact by smacking the 'DART' satellite into the smaller asteroid at a speed of about 4 miles per second in an attempt to alter its course around its partner. It is expected to collide with its target on September 26th, 2022.
The spacecraft is roughly the size of a small car. It leverages several new technologies as well as a number of existing ones. The vehicle gathers solar energy using Deployable Space Systems Roll-Out Solar Arrays (ROSA). This will be the first time these arrays are used in deep space, having been tested aboard the International Space Station in 2017. The Didymos Reconnaissance and Asteroid Camera for Optical Navigation (DRACO) will be used to photograph the asteroid system as the craft approaches, as well as provide visual data for telemetry. 'DART' receives its thrust from a single NEXT–C ion engine, which uses small amounts of electricity to push ionized xenon gas through an electrified grid. This efficiently produces up to 236 newtons of thrust in vacuum, which can accelerate a spacecraft to blistering speeds over long periods of time while using remarkably little fuel. NASA developed this technology at the Glenn Research Center in collaboration with Aerojet Rocketdyne. NASA hopes to use this mission as a demonstration and to make this engine a staple for future spacecraft. The Spiral Radial Line Slot Array (RLSA) is a new type of high gain communication antenna, the first of this model to be flown in space. It will communicate directly with NASA's Deep Space Network.
However, the DRACO (Didymos Reconnaissance & Asteroid Camera for OpNav) imaging instrument is based on the LORRI high-resolution imager from the New Horizons spacecraft, which rendezvoused with Pluto in July of 2015. 'DART' will also be carrying a passenger, LICIACube (Light Italian CubeSat for Imaging of Asteroids), designed by the Italian Space Agency. It will detach from 'DART' 10 days before impact and send back images of the ejecta created by the encounter. A follow-up mission led by the European Space Agency is expected to launch in 2024 and arrive at Didymos in 2027. It will complete a more detailed assessment of the impact and verify findings from ground-based telescopes.
NASA illustration of the 'DART' spacecraft
An Ion Thruster being tested in a vacuum chamber at NASA's Glenn Research Center
(Photos: Jon Reino, SN)
Although there are no known Near-Earth Objects (NEOs) that pose a significant threat to Earth within the next 100 years, developing this technology now is critical to deploying countermeasures against any potential impacts in the future. The highest risk is posed by asteroid 2009 FD, with about a 1 in 714 chance of impacting Earth in 2185, less than 0.2%. More than 19,000 near-Earth asteroids have been discovered, with about 30 new ones being spotted every week on average. Most of these discoveries have been made by ground-based telescopes funded by NASA's Near-Earth Object Observations Program.
The impact is only expected to alter the velocity of Dimorphos by 0.4mm/sec. That might not seem like much, but with enough warning that could make the difference between an asteroid making a devastating impact with our home planet and passing us harmlessly. This scenario is not just a Hollywood trope; it plagues the minds of many scientists, including Bill Nye. At the 2019 Planetary Defense Conference hosted by the International Academy of Astronautics he said, "It's a very low probability in anyone's lifetime, but it's a very high-consequence event. If it happens, it would be like control-alt-delete for everything."
Sequential radio images of Didymos and its moonlet taken by the Arecibo Observatory on 23, 24 and 26 November 2003
Although the historic Arecibo Observatory has fallen into disrepair since its receiver platform collapsed into the main dish in December 2020, many ground-based observatories are ready to study Didymos to observe the results of the 'DART' impact. Notably, The Infrared Telescope Facility (IRTF) located at the summit of Maunakea on the Big Island of Hawaii, which hosts a diverse range of programs to study, monitor, and discover new NEOs. Observatories worldwide will provide valuable data about the minute changes in the moonlet's orbit around Didymos.
While we wait for 'DART' to arrive at Didymos, the search for NEOs continues. The Large Synoptic Survey Telescope (LSST) at the Vera C. Rubin Observatory in Chile is expected to capture its first light next year. It uses a 3.2-gigapixel CCD imaging camera, the largest digital sensor ever built, and will capture a detailed picture of the entire sky every few nights. This will allow researchers to spot small changes in the movement of objects, which is how new NEOs are located. 'DART' represents the first real attempt to alter the course of an asteroid, albeit on a relatively small scale. Testing the concept of kinetic deflection now will lay the groundwork for future experiments and the development of technologies that might someday save the world, literally.
Visit https://www.nasa.gov/planetarydefense/dart for more information on this mission.
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