On 12 March 2025 ESA’s Hera spacecraft for planetary defence performs a flyby of Mars. The gravity of the red planet shifts the spacecraft’s trajectory towards the Didymos binary asteroid system, shortening its trip by months and saving substantial fuel.

This is a simulation of that flyby, with closest approach to Martian moon Deimos taking place at 12:07 GMT and Mars occurring at 12:51 GMT. It was made using SPICE (Spacecraft, Planet, Instrument, C-matrix, Events) software. Produced by a team at ESA’s ESAC European Space Astronomy Centre, this SPICE visualisation is used to plan instrument acquisitions during Hera’s flyby.

Hera comes to around 5000 km from the surface of Mars during its flyby. It will also image Deimos, the smaller of Mars’s two moons, from a minimum 1000 km away (while venturing as close as 300 km). Hera will also image Mars’s larger moon Phobos as it begins to move away from Mars. In this sped-up simulation, Deimos is seen 30 seconds in, at 12:07 GMT, while the more distant star-like Phobos becomes visible at two minutes in, at 12:49 GMT.

The spacecraft employs three of its instruments over the course of these close encounters, all located together on the ‘Asteroid Deck’ on top of Hera:

Hera’s Asteroid Framing Camera is formed of two redundant 1020x1020 pixel monochromatic visible light cameras, used for both navigation and science.

The Thermal Infrared Imager, supplied by the Japanese Aerospace Exploration Agency, JAXA, images at mid-infrared wavelengths to determine surface temperatures.

Hera’s Hyperscout H is a hyperspectral imager, observing in 25 visible and near-infrared spectral bands to prospect surface minerals.

Did you know this mission has its own AI? You can pose questions to our Hera Space Companion!