The European Space Agency's Hera spacecraft has captured the first clear image of the asteroid pair Didymos and Dimorphos as separate objects. On October 18, while positioned 1,280 kilometers from its targets, Hera's Asteroid Framing Camera resolved Dimorphos as a distinct point for the first time, though it appeared as just one pixel in the image.
Michael Kueppers, a mission scientist, noted the breakthrough: "Before this acquisition, the spacecraft was still resolving the Didymos system as a single dot. But now, even though Dimorphos is made up of only around one pixel in this initial image, it is clearly well separated from its parent body."
The asteroid pair currently sits 197 million kilometers from Earth. Dimorphos measures about 151 meters across, while its larger companion Didymos spans approximately 780 meters in diameter. Dimorphos orbits Didymos at an average separation of 1.15 kilometers at a speed of roughly 18 centimeters per second.
Earlier in October, Hera conducted two thruster firings spaced one week apart to reduce its approach speed to 20 meters per second. Mission manager Ian Carnelli stated that detailed images of Dimorphos will be released on November 25.
Hera is investigating the aftermath of NASA's Double Asteroid Redirection Test (DART), which deliberately struck Dimorphos on September 26, 2022, at approximately 6.1 kilometers per second. The impact shortened the asteroid's orbital period by roughly 33 minutes and ejected debris as far as 10,000 kilometers into space. However, the orbital change exceeded predictions from computer simulations, leaving open questions about the asteroid's physical properties and composition.
Over the coming months, Hera will conduct a detailed investigation using multiple scientific instruments and will release two small CubeSat satellites to gather observations from closer distances.