The European spacecraft Hera, built for planetary defense, has for the first time been able to distinguish the two asteroids that are its target. The European Space Agency (ESA) reported this. The Didymos system is located about 197 million kilometers from Earth.
The image was taken by the monochrome Asteroid Framing Camera on the evening of Friday, October 18, when the probe was 1,280 kilometers from the pair of asteroids. The image showed for the first time the smaller part of the system, the asteroid Dimorphos.
"Until now the spacecraft saw the Didymos system as a single point. Now, although Dimorphos occupies only about one pixel in this first image, it is clearly separated from its parent body," explained Michael Kueppers, as quoted by ESA.
The image was preceded by successful braking maneuvers. Two engine burns a week apart reduced the spacecraft's speed relative to the asteroids to 20 meters per second, allowing it to approach the target gradually and precisely.
The sizes of the objects are as follows: Dimorphos is 151 meters across, roughly like the Great Pyramid of Cheops, while Didymos is 780 meters in diameter, slightly less than the height of Dubai's Burj Khalifa skyscraper. The asteroids orbit a common center of mass at an average distance of 1.15 kilometers from each other, with Dimorphos moving around Didymos at about 18 centimeters per second.
"For the first time we see with Hera's own eyes the binary asteroid system for which the mission was created. As we get closer, the images will become much sharper. The first detailed images of Dimorphos, the first object in the Solar System whose orbit was measurably changed by humans, we will present on November 25," added mission head Ian Carnelli.
Recall that on September 26, 2022, Dimorphos became the object of a large-scale planetary defense experiment: a probe from the U.S. National Aeronautics and Space Administration (NASA), DART, struck this small asteroid at a speed of 6.1 kilometers per second. The collision ejected a plume of debris about 10,000 kilometers long into space, and the asteroid's orbital period was shortened by about 33 minutes.
However, a number of key questions remain, without answers to which the "kinetic impact" method will not become a fully understood planetary defense technology. What happened to the asteroid itself? Did a crater remain on it, or was its shape completely changed? What are the exact composition, structure and mass of Dimorphos, and what properties explain the deflection, which turned out to be significantly stronger than collision models predicted?
In the coming months Hera will conduct a detailed "crash site investigation" on Dimorphos. Several instruments will be used for this, as well as two cubesats, miniature satellites the size of a shoebox, which will allow even closer study, up to landing.