Bullseye For DART Mission

Image Credit: NASA/Johns Hopkins APL/Steve Gribben

BULLSEYE

For DART Mission

By Jodie Sims

On 24th November 2021, NASA launched an ambitious mission called DART (Double Asteroid Redirection Test) as part of their planetary defense program. This mission launched from the Vandenberg Space Force Base onboard a SpaceX Falcon 9 rocket and was destined for an impact with the asteroid Dimorphos, to see if we could change its trajectory. We have never before tried to change the path of any celestial body. For the first time in history, Earth is striking back!

Dimorphos, is a 160m wide minor-planet moon with a 12-hour orbit time of the near-Earth asteroid 65803 Didymos. Didymos, which means twin in Greek, is a sub-kilometre asteroid measuring a total of 780 m wide that falls into the category of potentially hazardous asteroids and a near-Earth object (NEO) of the Apollo group. This group of asteroids are particularly hazardous due to their elliptical orbit with a perihelion less than 1.017 AU passing close to both Earth and Mars. Most asteroids lie between Mars and Jupiter in an enormous ring known as the asteroid belt. This belt of rubble is left over from the formation of our solar system 4.6 billion years ago and holds more than 200 asteroids larger than 100km in diameter.

As of April 2022, a total of 28,772 near-Earth asteroids have been discovered and 878 have a diameter of one kilometre or larger. This particular NEO is situated 11 million kilometres from Earth. The main objective of the DART mission was to determine how much DART’s kinetic impact could alter Dimorphos’ velocity by measuring the change in its orbit around Didymos once impacted. This technology may then be used in the future to deflect any potential asteroids on a collision course with our home planet.

The main DART body measured 2.6m across and weighed 600kg, driven primarily by DRACO (Didymos Reconnaissance and Asteroid Camera for Optical Navigation). A camera imaging the approach to the asteroid system using a star tracker for positioning in space. DRACO was the eyes feeding the images to SMART Nav (Small body Manoeuvring Autonomous Real Time Navigation). Using computational algorithms SMART Nav guided DART autonomously. Any small errors in the positioning system could have spelled disaster for the mission.

Adjoining DART was a small, shoe box sized spacecraft built by the Italian Space Agency (ISA), know, as the Light Italian CubeSat for Imaging Asteroids (LICIACube). It was DART itself that collided with Dimorphos; the job of LICIACube, when separated from DART on Sept. 11, was to fly close by and take images of the moonlet before and after the impact. Precise measurements of the orbit before and after impact was also taken by an array of Earth-based telescopes, including NASA’s Deep Space Network of radio telescopes in Barstow, California, Madrid, Spain, and Canberra, Australia.

DART intercepted the small moonlet asteroid at 7:14 p.m. EDT on September 26th, 2022. Impacting at a speed of approximately 6.6 kilometres per second creating a plume of debris caught on camera by LICIACube. On the 11th of October after critical examination of all the data collected NASA announced the DART mission a resounding success, confirming it had shortened Dimorphos’ orbital period around Didymos by approximately 32 minutes.

Throughout history there has been more than 30,000 meteorites discovered on the surface of the Earth ranging in size. With an estimated 40,000 metric tons of space debris falling to earth each year. Thankfully asteroids large enough to cause catastrophic damage very rarely hit earth with the last known impact 66 million years ago. This cataclysmic event occurred when a 10 to 15 km diameter asteroid crashed off the Yucatan Peninsula causing a mass extinction event that wiped out the dinosaurs.

On a smaller scale more recently on the 15th February 2013, a large explosion from an object entering our atmosphere occurred in the skies above Chelyabinsk just to the east of the Ural Mountains in southern Russia. Most of the object burned up in the atmosphere, but some pieces made it down to Earth. One smashed through the ice of the frozen Lake Chebarkul, leaving a hole 7 metres wide. This debris was recovered by divers in October 2013 and weighed in at 570 kilograms. Astronomers estimated from the debris collected that the explosion was an asteroid 17 to 20 metres across with a mass of 10,000 tonnes. The initial blast, at an altitude of about 30 kilometres, carried an energy equivalent to 500 kilotons of TNT – about 30 Hiroshima bombs.

Other smaller objects have occasionally been known to hit people, but there have been no confirmed deaths in modern history. One such incident occurred in November 1954. A small meteorite crashed through the roof of a house in Alabama, bounced off a piece of furniture and hit 34-year-old Ann Elizabeth Hodges. Amazingly she survived to tell the tale.

A fantastic place to keep an eye out for potential impacts is the Sentry Earth Impact Monitoring database. Sentry is an automated collision monitoring system that scans the current asteroid catalogues for potential future impacts with Earth over the next 100 years. Daily observations and orbit calculations for Near-Earth objects are received and inputted from the Minor Planet Centre Cambridge, Massachusetts. Even though there has not been a major asteroid collision for millions of years there is always the potential that a large asteroid could be on a collision course with the Earth.

However, DART has shown that Earth has never been more equipped to monitor and deflect potential galactic threats than now and planetary defence will continue to improve into the future with the ultimate goal of protecting humanity.

Image Credit:

Left Image: The launch of the Dart Mission on a Falcon 9 Rocket. Mashable India

First Image: DART mission by NASA above asteroid Didymos on its way to the moonlet Dimorphos. The Global Economics

Second Image: Hubble Space Telescope shows a split stream of dust and rock streaming off the Moonlet Dimorphos. NASA, ESA, STSCI, HUBBLE

Third Image: Plumes of debris erupting out of the asteroid Dimorphos. ASI Italian Space Agency

Fourth Image: DART’s Final Images Prior to Impact. NASA/ Johns Hopkins APL