Solar Orbiter grazed Earth, a live passage amid debris

The Solar Orbiter space probe took off in February 2020, but this weekend it made a passage closer to the Earth in order to take advantage of its gravitational force.

The main mission of ESA’s Solar Orbiter is to study the Sun, and the impact of the latter in “stellar weather”. This mission, which requires certain technical prerequisites, the probe is about to begin. Because carrying out a mission to the Sun is always complicated. The question of gravitational assistance arises very quickly when we know the millions of kilometers which separate our planet from our star of the day.

Thus, in order to spend as little fuel as possible during this trip, the probe uses the planets it encounters during its journey to gain speed and modify its trajectory thanks to the gravitational power of the latter. A process that is ultimately quite common in the space industry.

A stealthy return above Earth

Solar Orbiter, which had yet left Earth more than a year and a half ago, found itself this weekend less than 500 kilometers from the Earth’s surface. It was in fact expected that Solar Orbiter would cross (very) closely the Earth’s route so that the latter catapulted it towards the Sun.

A passage closer to Earth, just above North Africa, which took place on November 27 in the early morning. While it was only 5 a.m. in Paris, the teams in charge of the probe were already on the war footing, the probe being as close to Earth as possible.

Because there was one thing that worried scientists more than anything else. The risk of collision with orbital debris. Indeed, the Earth’s orbit is polluted by thousands of debris. These, sometimes too small to be detected on radars, are a real danger for the probe. During its descent towards Earth it first crossed the orbit of geostationary satellites.

A descent in the middle of the debris

They are 36,000 km above us and rotate at the same speed as the Earth. In this very strategic orbit, the traffic is already disrupted, but the probe was not at the end of its troubles, it which descended even lower, towards the satellites in orbit around 400 kilometers.

In this low area of ​​the sky, which knows the ISS, for example, satellites are legion. But so is the debris. The probe must therefore succeed in crossing this area without encountering the slightest incident, which could have ended the mission.

Scientists therefore remained on the war footing for nearly 24 hours, before being able to catch their breath once the probe was removed from Earth. It is therefore now heading towards the Sun, over the next few months it should pass as close as possible to Venus to use it as an anchor point so as not to be sucked in by the star of the day during its mission.

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