WORLDTECHHera spacecraft resolves Didymos pair as two separate asteroids
For the first time, the European Space Agency's Hera spacecraft has resolved its two target asteroids as separate objects, exposing the binary structure of the Didymos system from roughly 197 million km away. The agency presents the image as a milestone for a mission built around planetary defence.
First separate view of the asteroid pair
Hera captured Didymos and its companion Dimorphos with its monochromatic Asteroid Framing Camera on the evening of Friday 18 October, from a distance of 1280 km. In that frame the smaller Dimorphos stands out as a distinct object for the first time. Until then the spacecraft had registered the Didymos system only as one point of light.
Dimorphos fills just one pixel in the initial picture, yet it is clearly set apart from its larger parent body, the agency quotes Michael Kueppers as saying.
Braking manoeuvres came first
The image followed a successful run of braking manoeuvres earlier in the month. Two thruster firings, separated by a week, brought the spacecraft down to 20 m/s relative to its two targets, letting it close in through carefully tuned steps.
Size and orbit of the Didymos system
Dimorphos measures 151 m across, about the height of the Great Pyramid of Giza, while the 780 m Didymos is slightly smaller than Dubai's Burj Khalifa. The two bodies orbit an average of 1.15 km apart, with Dimorphos circling its parent at about 18 cm/s.
The source material also recalls an earlier episode in the system, when a collision threw a plume of debris across 10 000 km of space and shortened the asteroid's orbit by around 33 minutes.
Open questions
- How much of Dimorphos's surface will Hera be able to resolve as the spacecraft closes in?