An asteroid, a spacecraft, and a big crash. This is American space agency NASA's DART mission, humanity's first attempt to try and eliminate space threats to Earth.
DART stands for Double Asteroid Redirection Test. The spacecraft was launched into space in November 2021, and is now finally ready to carry out its mission.
As part of the mission, a NASA spacecraft will crash into an asteroid to test planetary defence techniques. The DART crash-test is planned for 26 September. NASA's objective is to change the asteroid's path in space.
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NASA has carefully chosen a particular asteroid for the mission. The target is Didymos, a double-asteroid system in our solar system. Didymos is a near-Earth asteroid system orbiting the Sun. The system consists of Dimorphos, an asteroid moonlet orbiting the larger Didymos asteroid. Dimorphos will be around 11 million km from Earth when NASA's DART crashes into it. While Didymos is 780m in diameter, Dimorphos is 160m in diameter. Both Didymos and Dimorphos do not pose a threat to Earth.
In its mission, NASA does not want to destroy the asteroid. Instead, the space agency wants to test a different technique of getting rid of threatening space objects.
The DART mission is the world's first test of kinetic impact technique. This relies on kinetic energy to displace an asteroid. Kinetic energy is energy possessed by an object which is in motion. The kinetic energy will be transferred to the asteroid when the spacecraft crashes into it. The ultimate aim is to be able to change an asteroid's path in space away from Earth. NASA wants to test changing the speed and path of an asteroid.
While the mission may seem straightforward, it consists of many complicated stages.
Also, the final impact will take place without any human intervention, so preparations have to be flawless.
In the run-up to the impact, the DART team will continue making trajectory corrections till 24 hours before the crash. By 25 September, the target's position will be known within 2 km. From this point on, the DART craft has to guide itself autonomously until it hits the asteroid without any human guidance.
The impact is slated to take place at 7:14 pm EDT on 26 September. In India, the time would be 4:44 am on 27 September. The DART craft will hit the asteroid at an astounding speed of 6.6 km per second. Onboard systems will keep sending images to Earth till the last minute. A small craft named LICIACube will detach itself earlier to record the impact from a distance.
NASA scientists estimate that the crash will change the asteroid speed by less than 1%. This would result in the asteroid's orbit time being altered by many minutes. This change should be enough to be seen from Earth. Also, scientists will compare the results of the impact and computer simulations to see their efficiency.
An asteroid hitting Earth is believed to have wiped out the dinosaurs. Therefore, NASA takes the threat of killer space objects very seriously.
The threat is posed by Near-Earth objects which are asteroids and comets revolving around the Sun. Their orbit can bring them close to Earth, thus becoming a threat. NASA has set up the Planetary Defense Coordination Office, or PDCO, to monitor this. PDCO provides early detection of potential threats. These include near-Earth objects within 5 million miles of Earth's orbit. Objects 30-50 metres in size are big enough to damage the Earth's surface.
The PDCO searches for such space objects, maps their orbits, and measures their physical features. The PDCO also sponsors studies on methods to eliminate these space threats.
If an asteroid has a chance greater than 1% of hitting Earth over the next 50 years, it is classified as a significant threat. Here is what happens next.
The PDCO is supposed to notify NASA about the space object posing a threat. NASA will then inform the US President and the US Congress. American government departments and agencies will also be notified. PDCO and government agencies maintain a Preparedness Strategy and Action Plan for such situations. The PDCO is also mandated to help the Federal Emergency Management Agency or FEMA. Their job is to prepare emergency responses if the asteroid impact cannot be avoided.
As humans rapidly move towards becoming a space-faring people, development of technology to get rid of space threats is a logical step. However, we must not keep their eyes towards the stars, and forget the existential threats facing us right at home.