65 million years ago, the Chicxulub asteroid that crashed into the earth caused the extinction of 75% of all species, including dinosaurs. From that time until today, the Earth was hit by small asteroids. There is a possibility that a small asteroid will fall on your head even at the moment. Depending on the size of the falling asteroid, it is determined whether it will destroy a house, a village, a city, a country, a continent, or the entire Earth. So the Earth's living system is not capable of eliminating the threat from asteroids.
Because of this, a large number of telescopes around the world are monitoring the sky 24x7x365 and working to find asteroids. You sleep soundly at night and astronomers around the world are studying the data from these telescopes and calculating the paths of asteroids for the safety of the entire planet. So far, scientists have discovered more than 6 lakh asteroids, and among them, there are 130 asteroids with a probability of more than 0.01% hitting the earth in the next 100 years. But those are just the asteroids that have been found. An undiscovered asteroid may be headed for Earth right now.
What do we do if we somehow find an asteroid that has a high probability of hitting Earth one day, or an asteroid that is certain to hit Earth? With current technology, it would be possible to send a spacecraft to collide with the asteroid before it gets close to Earth. The collision causes the asteroid's path to change slightly and with time this changes significantly. Therefore, the earlier this collision can be done, the greater the amount that can change the path of the asteroid.
So NASA decided a few years ago to conduct a rehearsal for this task right now without waiting for an asteroid to aim at Earth. A spacecraft aimed at an asteroid that is harmless to Earth will collide with the asteroid in a few days and change its trajectory.
In this mission called Double Asteroid Redirection Test (DART), a spacecraft with a mass of 610 kg will collide with the satellite named Dimorphos, which is orbiting the Didymos asteroid. The mission is nicknamed Double Asteroid because of the system that has two asteroids. Why does this spacecraft collide with an asteroid in orbit around an asteroid instead of an asteroid orbiting the sun?
This is because the change in trajectories caused by the collision must be observed. The period of asteroids orbiting the Sun can be months or years. The collision of this DART causes a very small change in velocity. Because of this, it is difficult to observe the change in the path or period of an asteroid with a large periodic period from Earth. But Dimorphos takes only 11.92 hours to orbit Didymos. Therefore, even if there is a few-minute difference in the cycle time, it is a significant difference in the total cycle time.
Unlike NASA's regular spacecraft, the DART will not carry any scientific instruments. The basic equipment included here is the equipment that will automatically find its way to collide with Dimorphos. The camera called Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO) is the main equipment among this equipment. The plane is controlled by the Small-body Maneuvering Autonomous Real-Time Navigation (SMART Nav) software which calculates the route based on the photos received from this camera.
In addition, there is another small spacecraft that is carried on board the DART. The task of the small spacecraft LICIACube (Light Italian CubeSat for Imaging of Asteroids) provided by the Italian Space Agency is to monitor the collision. The plane separates from the DART before the collision and then moves behind the plane to photograph the event.
SpaceX has won the contract to launch the DART. Launched from the earth by a Falcon 9 rocket on November 24, 2021, at 11.51 Sri Lanka time, the plane is nearing the end of its journey of almost a year.
The 800-meter-diameter asteroid Didymos was caught by the spacecraft's DRACO camera on July 27. It is about 32 million kilometers away from the asteroid system. Aiming at the ever-closer asteroid system, the spacecraft set its course and on September 12, the LICIACube was released. The collision between the Dimorphos and DART is scheduled to take place on September 27.
4 hours before the collision, the complete control of the aircraft is handed over to SMART Nav software. The Dimorphos satellite has a diameter of 170 meters. Because of this, the aircraft can see it about an hour before the collision. It is about 24,000 kilometers away. SMART Nav software is responsible for automatically aiming the spacecraft towards the center of the satellite as it approaches the satellite at a speed of 24,000 km/h. A finishes course correction with 2 minutes remaining before the collision. By that time, the fate of the plane was decided.
The Dimorphos satellite will collide with the DRACO spacecraft, which will transmit images to Earth until the moment of the collision. The collision was observed not only by telescopes on Earth but also by the Hubble Space Telescope, James Webb Space Telescope, and the Lucy spacecraft. NASA hopes to live-stream the last few hours of Earth's first planetary defense mission. You can also watch it from the link below.
About 3 minutes after the collision, the LICIACube, which arrived behind, takes pictures of the collision. The flight path has been prepared so that this plane does not crash. Then the images will be transmitted to Earth. Telescope systems around the world will continue to monitor Dimorphos for the next several months to properly quantify the change in its orbit.
By comparing the observed difference with the originally calculated difference, it will be possible to know the accuracy of the mission and the nature of the asteroid. In this way, it is hoped to obtain the practical knowledge needed for an operation to change the path of an asteroid that may threaten the Earth in the future.
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