Tomorrow morning, the European Space Agency’s (ESA’s) Hera spacecraft will perform a flyby of Mars, using the Red Planet’s gravity to adjust its path towards the Didymos binary asteroid system. During the flyby, Hera will take close-up images of Deimos, one of Mars’ two moons. Starion’s experts, who have supported the planning of the flyby since before launch, will use these images to help calibrate Hera’s instruments before it reaches the asteroids.
In 2022, NASA’s DART mission crashed into Dimorphos, the smaller of two asteroids that form the Didymos binary asteroid system. This was the first of two stages in an experiment designed to help us learn more about these asteroid systems and explore options to deflect asteroids that may collide with Earth in future.
Now, with support from Starion’s engineers based at ESA’s European Space Astronomy Centre (ESAC), ESA’s Hera spacecraft is about to perform a gravity assist flyby of Mars as part of a follow-up mission to Didymos. Importantly, it will also offer the opportunity to study Mars’ moon Deimos from close range and use that to calibrate Hera’s instruments before it reaches the asteroid pair.
In advance of the flyby, the SPICE[1] software operations team at ESAC, led by Starion’s Alfredo Escalante Lopez, ESA Spice Work Package Manager, took predictions of the spacecraft’s trajectory and attitude from the mission’s flight dynamics team and converted these into the SPICE format. This was then made available to the spacecraft’s instrument teams to help them plan an observation timeline for Hera’s Asteroid Framing Camera (AFC), Thermal Infra Red Imager (TIRI) and Hyperscout hyperspectral imager. Other members of the SPICE team working on Hera include SPICE Service Engineers Ricardo Vallés from Starion and Rafael Andrés from Aurora.
Simulation of Hera’s instrument’s field of view during the Mars/Deimos flyby using the Cosmographia tool
“The field of view of the AFC camera is very narrow – just a few [5.5] degrees – and the flyby will be very fast, so the observation timing needed to be planned extremely carefully,” explains Alfredo Escalante Lopez.
“As the flyby happens, we will analyse the images in real time, using telemetry and trajectory data given to us by the flight dynamics team, to support calibration of the instruments. By comparing the images with our original simulations made using the Cosmographia tool[2], we can then provide SPICE data kernels that will let the instrument teams correct issues such as misalignment or optical distortions that may have been caused by factors such as vibrations during launch, and optimise aspects like the image exposure times.
“Calibrating the instruments before Hera reaches Didymos will let scientists start making observations straightaway when they reach the asteroids, saving precious time. Deimos’s size and type makes it an ideal candidate for this task – it’s the only such object Hera will pass, so all our preparation and then our work during the flyby is really essential for the success of the mission. The flyby also provides an opportunity to take one of the best ever images of Deimos compared with what can be captured by Mars missions such as Mars Express or the ExoMars Trace Gas Orbiter, due to Hera’s trajectory as it flies past this moon.”
Further information
Deimos, the smaller of Mars’ moons, orbits the Red Planet at a distance of 23,460km. The moon has a diameter of 12.4km, an uneven body and a dark surface reminiscent of C-type asteroids.
Hera will take images of Deimos from around 1,000km and of Mars from around 5,000km, making its closest approach to Mars at 13:50 CET on 12 March. Images from the Mars and Deimos flyby are expected to be released in the evening of 12 March.
About SPICE and Cosmographia
[1] Find out more about SPICE and the ESA SPICE Service
[2] The SPICE-enhanced Cosmographia tool is freely available for download, along with the required catalogue files for each mission, including Hera, at: cosmos.esa.int/web/spice/cosmographia
Additional Cosmographia simulations
Simulation of Hera’s trajectory from Earth to the Didymos asteroid system using the Cosmographia tool
Simulation of Hera’s flyby of Deimos and Mars using the Cosmographia tool
Main image: credit ESA Science Office
