DART Spacecraft Is On Its Way To Smack An Asteroid And Move It Off Course In Humanity’s First Test Of ‘Planetary Defence’

A mission to crash a spacecraft into an asteroid in order to move it off course ever so slightly, yet carrying huge significance for the planet’s long-term future, lifted off yesterday, 24 November, at 6:21 UTC (11:51 IST).

The DART mission, short for “Double Asteroid Redirection Test”, took off for the skies on board a SpaceX Falcon 9 rocket from Vandenberg Space Force Base in California, United States of America (US).

After a 10-month journey, towards the end of September 2022, the DART spacecraft will smash into an asteroid system with the goal of deflecting it — so that Earthlings can be better prepared in the future if a potentially hazardous asteroid happens to be headed right in the direction of the blue planet.

Accompanied by the high-resolution imager DRACO, which will perform the twin role of snapping images of the asteroid system upon approach and support the autonomous guidance system, DART will look to accomplish a test of a particular asteroid deflection technology.

“The DART mission is NASA's demonstration of kinetic impactor technology, impacting an asteroid to adjust its speed and path,” the mission overview, published by the Johns Hopkins University Applied Physics Laboratory, says.

The Johns Hopkins University Applied Physics Laboratory is leading the mission for the US space agency National Aeronautics and Space Administration (NASA) alongside other players like the Planetary Defense Coordination Office, several NASA centres like Goddard Space Flight Center, Langley Research Center, and Marshall Space Flight Center, and various astronomical observatories.

The DART spacecraft’s target is the binary asteroid system Didymos, which comprises the larger asteroid Didymos, 780 metres in diameter, and the smaller moonlet (secondary) asteroid Dimorphos, 160 metres in diameter, which orbits the larger asteroid.

The spacecraft will collide with the smaller sibling, Dimorphos, at a rapid clip of 6.6 kilometres per second with the goal of shaving off a few minutes off its orbital period around Didymos. Scientists reckon that this would be enough to prevent a collision with Earth if the asteroid were to be on a collision course with our planet.

However, since this is only a test of the technology, the asteroid system chosen for the DART mission will only be flying by Earth at a comfortable distance of roughly 11 million kilometres when the intentional crash occurs. The asteroid pair is, therefore, not a threat to Earth.

Many Earth-based telescopes will catch the impact and measure its effects — the data will tell scientists how effective it is to bump an asteroid off course in order to protect the Earth, with the added benefit of validating computational models of these events developed in laboratories.

Scientists will be able to note a change (if there is any) by using the smaller asteroid’s periodic eclipsing of the larger asteroid (as seen from here on Earth) to record the regular variation in brightness before and after the asteroid impact.

According to NASA’s estimate, no known asteroid larger than 140 metres in size — the test asteroid Dimorphos is about 20 metres bigger — has a significant chance to hit Earth for the next 100 years. However, only about 40 per cent of those asteroids have been found as of October 2021.

The DART mission is part of NASA's larger planetary defence strategy. Planetary defence involves identifying potential asteroid or comet impacts with Earth and then being able to respond in order to either prevent or mitigate the possible effects.

The Planetary Defense Coordination Office (PDCO) has been leading the planetary defence efforts for NASA since the formation of the specific office in 2016.

Among its objectives are early detection of potentially hazardous objects (PHOs), issue of warnings of possible effects if an impact were to occur, and leading the coordination of US government efforts to respond to an impact threat.

Scientists are generally on the lookout for near-earth objects, which are asteroids and comets going around the Sun and which at some point may pass by close enough to the Earth — within about 50 million kilometres of the Earth’s orbit.

PHOs, whose early detection is the job of the PDCO, are near-earth objects that are large enough (30-50 metres) to cause significant damage on Earth and are predicted to come within 8 million kilometres of Earth's orbit.

In February 2013, an asteroid missed the sharp eyes of telescopes to impact Earth and explode over Chelyabinsk, Russia, releasing the same amount of energy as 500 kilotonnes of TNT.

The size of the asteroid was just 18 metres and yet enough to cause a blast that injured more than 1,600 people and led to an estimated $30 million in damage.

“It was a stark reminder that potentially hazardous objects can enter Earth’s atmosphere at any time, and that even relatively small ones can be of concern,” NASA says.

The PDCO came into being three years later, and a further five years down the line, the DART mission is underway to prepare the ground for planetary defence.

The method employed in the DART mission, called kinetic impact deflection, is only one of the ways to protect ourselves from incoming space debris. Gravity tractor and blast deflection are two other mitigation methods available to scientists.

In the gravity tractor method, the gravity of a spacecraft is used to slowly steer the asteroid off its path. The way it would work is that a gravity tractor device would fly alongside the asteroid for a long period of time (for decades even) and divert the asteroid. This method offers the greatest control among the available options.

Blast deflection, as the name suggests, would take a huge blast in space to deflect — or even destroy, if necessary — an asteroid.

Experts have proposed nuclear explosives as the source of the blast in space. But there are things to consider with the blast deflection technique — the use of nuclear explosives anywhere, let alone in outer space, is no small matter and, besides, blowing up an asteroid to create many more fragments that will float in space itself isn’t a comfortable prospect.

But it’s said that blast deflection will be the most effective for diverting an approaching near-earth object.

At this point in time, however, kinetic impact deflection is at the most technologically mature stage — and hence, DART is in motion, both the mission as well as the spacecraft, in order to try and lay the building blocks of Earth's defence for the future.