Here we are again, at Frankfurt Airport, after another successful milestone for Hera. On March 12, around midday, Hera performed a flyby of Mars, meaning that she "stole" some of its energy to receive a push toward her final target, Didymos. This kind of technique is quite common in space travel, as it drastically reduces the amount of propellant needed onboard. In fact, Hera received an additional push of almost 1 km/s, which would be equivalent to her entire fuel reserve!
Of course, that was not all. Since the GNC is functioning well, and the autonomous navigation using centroiding technologies was already successfully executed the day after LEOP, the idea was to go further and test a fully experimental technique called feature tracking, using Mars as the target. GMV implemented that algorithm with low priority, as Hera's schedule was very tight and prioritization was crucial. The plan was to use it only after the mission's main objective had been achieved. However, we dared… and we succeeded!
The major concern in the ESOC control room in Darmstadt, Germany, was that a safe mode could be triggered due to this test, which would have reduced the amount of scientific data from the Mars flyby. However, testing this technology would provide additional flexibility for close proximity navigation when Hera approaches the asteroids. It was a trade-off, as always, but we need to trust our system, knowing that we will have to face an unknown environment (such as a double asteroid system) with very little time to adjust or adapt to the unexpected. So, the choice was made: "green light" for feature tracking on Mars.
We were there, together with Brian May from Queen (he has supported the mission from the beginning, as he is also a brilliant scientist, apart from being an incredible guitarist), watching a screen that was supposed to show us that at 16:05 on March 12th, we should receive a signal from the spacecraft. But seconds passed... minutes… and nothing. Luckily, it was just a frozen monitor that delayed the good news—Hera was alive, no safe mode was triggered, and everything was nominal.
We received amazing images of Mars and its moons like never seen before, and we are now ready to analyze the feature tracking results carefully. However, we can already say that it was a success. Performance was not the main goal, as the technology was designed for close proximity operations, such as lunar landings or close asteroid navigation, rather than a fast flyby of a planet. We know that features were identified on the planet, they were tracked between images, and the navigation filter used them to improve its state estimation.
Another milestone and another success for Hera, demonstrating the potential that "Next Space" missions can have.
In one year, we will conduct a deep-space maneuver, and six months after that, the real fun will begin: close proximity to a binary asteroid system that humankind has modified and about which we still have many unanswered questions, such as… can we defend Earth if something like what happened to the dinosaurs were to happen again?
A final remark to the Hera team… simply amazing! You are the true heart of the mission. Thank you, everyone.
Author: Andrea Pellacani
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