Paris (AFP)

More than 20 years that it has been revolving around the Earth to advance science: the International Space Station (ISS), which is about to welcome Thomas Pesquet, has over time become a cutting-edge laboratory, where weightlessness has not finished whetting the appetite of researchers.

Since the start of its construction in 1998, more than 3,000 experiments have been carried out at an altitude of 400 km.

Some turned towards the Earth, others towards space exploration, with the Moon and Mars now in sight.

The Station has reached its golden age, after a long phase of growth.

"It operates at 100% of its capacity, the use of the laboratory as initially thought is optimal", notes Sébastien Vincent-Bonnieu, who coordinates scientific experiments at the European Space Agency (ESA).

The interior of the ISS, as large as a football field, resembles a beehive where all spaces are occupied by astronauts, whose main task today is to carry out experiments, piloted by researchers from the Earth.

And to serve as "guinea pigs".

- "Mini-brains" -

Thomas Pesquet's second mission, "Alpha", promises to be busy, with a hundred experiments on the program.

Among them, "Cerebral Aging", to study aging on nerve cells in brains.

Or "Telemachus", an acoustic gripper for handling objects without contact, "Eco Pack", a new generation of packaging, blob breeding, a single-celled organism that fascinates biologists ...

"Some people ask what Thomas Pesquet is going to do better than during his first mission, Proxima. But nothing in fact, it's the same job," said Sébastien Barde, head of Cadmos, structure of CNES (the space agency French) responsible for micropensanteur activities.

The six laboratory technicians of the ISS take turns, some start a manipulation, others finish it.

"The experiments are designed for the long term, independently of the missions. Science gains a lot from it", develops the Cadmos engineer.

The study of weightlessness - or microgravity - has "gone from a pioneering era to something industrialized", with increasingly precise means of measurement: "Twenty years ago, there was no there was no ultrasound machine on board ".

Claudie Haigneré, the first French woman to fly in space, remembers an ISS "poorly equipped" at its beginnings, and "admires what it has become, with exceptional laboratories".

The "guinea pig" astronauts also stay longer: six months, versus a fortnight for the first manned flights;

measuring the effects of microgravity on their body is all the more relevant.

- "We are constantly learning" -

Up there, the human machine, hyper adapted to gravity, is shaken as in a shaker, and the degradation observed in the bones and arteries is close to cellular aging.

With the difference that when returning to the ground, the phenomenon is reversible.

"This is what is interesting: studying what the body brings into play to return to its balance, with possible avenues for treatment", analyzes Sébastien Barde.

"As much at the beginning of the space age, we needed the medical to go into space, as much today, it is the space which brings to the medical one because the weightlessness makes it possible to better understand diseases", a underlined the outgoing president of CNES, Jean-Yves Le Gall, on France Inter.

Osteoporosis, treatment against salmonellosis, water purification systems ... In 20 years, "major discoveries have been made there", according to the American historian Robert Pearlman, and others look "promising", like 3D printing of organs.

Voices have been raised against the cost of the ISS, deemed disproportionate in view of the discoveries, as NASA seeks to disengage to focus on distant exploration.

In 2019, ex-astronaut Patrick Baudry described the Station as a "canard".

“From the Soviet Mir station, we already know everything there is to know about the effects of microgravity on the body,” he criticized.

"Discussing the cost is one thing, but to say that we have done the tour is a bit silly. It's like asking whether to enlarge a telescope because we would have seen + enough + stars!", Replies the person in charge of Cadmos.

For some scientists, he insists, the ISS, which is scheduled to end in 2028, is "the only way to access their research themes", in medicine but also in material sciences, for which to overcome gravity is essential.

There will thus always be a community eager to study phenomena without gravity, thinks the physicist Sébastien Vincent-Bonnieu, who also notes a "growing" interest in orbit experiments.

In the ISS or elsewhere, like the future lunar orbital station.

© 2021 AFP