Image of Deimos (12,4 km), with Mars on the background, obtained with the HyperScout-H instrument on board the Hera spacecraft at a distance of 1024km. The planet appears blue in this near-infrared image image from the instrument. In the background, a variety of martian features can be observed, like the bright Terra Sabaea region at the top, close to the martian equator, or the 450 km-diameter Huygens crater to the bottom right of this bright region. (Credits: ESA)
ESA’s Hera mission for planetary defense performed a flyby of Mars, as part of its gravitational assistance manoeuvre to shorten its journey to the binary asteroid system Didymos. During the flyby, the spacecraft came around 5000 km from the surface of Mars, having also the opportunity to obtain images of its two moons, Deimos (during the approach) and Phobos (when departing Mars). Julia de León, Javier Licandro, and George Prodan, researchers at the Instituto de Astrofísica de Canarias, participate in this mission, successfully launched from Cape Cañaveral, Florida (USA) on October 7, 2024.
Hera is the first European mission for planetary defense that together with NASA’s DART (Double Asteroid Redirection Test) will study the effects of a tecnique for diverting asteroids called “kinetic impactor”. The DART probe crashed into the smaller (Dimorphos) of the two asteroids that form the binary system Didymos, on September 26, 2022. Hera will arrive at the system by the end of 2026 to carry out a detailed post-impact study.
Dr. de León, in addition to coordinate the Didymos observations from ground-based telescopes (including the Gran Telescopio Canarias), is responsible of the HyperScout-H instrument on board the spacecraft. This is a hyper-spectral camera that contains a detector covered by a thin layer of material in which there are 25 interference filters, each covering 5x5 pixels. “Due to the particularities of its design, we need observations of extended objects, that fully cover the field of view of HyperScout-H, in order to calibrate the instrument in-flight and perform a follow-up of its efficiency while in space. We will use images of the surface of Mars to that purpose”, says de León.
In addition, the two Martian moons are the scientific targets of the MMX mission (Martian Moons eXploration), of the Japanese Space Agency (JAXA), that will visit them after its launch in 2026, and will collect material from the surface of Phobos to bring it back to Earth. The observations of Deimos and Phobos by Hera have been coordinated with JAXA to maximize the scientific return of the two missions. “We will be able to observe the side of tidally-locked Deimos, the furthest of the two moons, that is facing away from Mars. As with our Moon, Deimos is offering always the same face to the red planet”, explains Licandro.
“The first and only images of that far-side of Deimos were obtained by the Hope probe, of the United Arab Emirates Space Agency, in February 2023, and none of them cover the spectral range where HyperScout-H operates, so our observations will fully complement these data and will help to optimize our instrument for our arrival to Didymos in 2027”, concludes de León.
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