Ariane 5 launches two satellites during its 7-year journey to Mercure – Astronomy Now

A powerful European rocket Ariane 5 took off last Friday from French Guiana and propelled a pair of satellites into space for a seven-year plunge into the interior solar system, a trip requiring seven planetary flyovers to slow down enough under the clutch of the sun. orbiting Mercury in hell.

The $ 1.9 billion BepiColombo project is only the second, after NASA's MESSENGER mission, to attempt to place a spacecraft in orbit around the innermost planet in the solar system. one of the most difficult technical missions of the European Space Agency and the Japanese Aerospace Exploration Agency, or JAXA.

The Ariane 5 rocket, the most powerful of the European inventory and one of the most reliable boosters in the world, was launched at 21:45. EDT (GMT-4, 10:45 am local time) and has moved majestically away from the Guiana Space Center on the north coast of South America.

The rocket was lighting up the European space base for tens of kilometers, east of the Atlantic Ocean, above a brilliant jet of flame emanating from its two solid fuel boosters. It accelerated quickly by burning five tons of propellant per second.

"It was fantastic!" Said Johannes Benkhoff, chief scientist of the BepiColombo project, after his first launch. "I had never seen it before and it was great. It was like a big ball of fire that was crossing the sky, it was really nice. "

The spacewalk went well and 27 minutes after take-off, the JAXA's Mercury Planetary Orbiter and Mercax Magnetospheric Orbiter satellites, both attached to a carrier, dubbed the Mercury Transfer Module, were released from platinum. top of the Ariane 5 to fly in their turn. own.

"Arianespace is delighted to announce that BepiColombo (is) in its targeted leak orbit and is now en route to Mercury," said Stephane Israel, Arianespace's President and CEO. "Today's new success marks the beginning of a seven-year journey for BepiColombo, which takes advantage of Earth, Venus and Mercury's gravitational assistance. What an exciting journey! "

While this may sound counterintuitive, you'll need more energy to reach Mercury (11.5 mph shifts) than NASA's New Horizon probe to reach Pluto.

The transfer module carrying the two satellites is equipped with ionic thrusters and more traditional liquid fuel rocket engines. But the lion's share of the energy needed will come from planetary flyovers, using the gravity of the Earth, Venus and Mercury to help determine trajectory and slow down, slowing enough the BepiColombo probe to reach an orbit around Mercury.

The inbound journey actually begins in April 2020, when the BepiColombo spacecraft travels over the Earth using the gravity of the planet to curve the trajectory on a trajectory carrying satellites to Venus. Two overflights of Venus are planned, one end 2020 and the other in August 2021, to deviate the trajectory towards Mercury.

But it's still not enough to do the job. Six overflights of Mercury are needed over the next four years to slow down the probe enough for it to be captured by the relatively low gravity of the planet.

This step will be taken in December 2025 when the ESA's MPO satellite and the JAXA MMO, then released from the space shuttle, will settle in different orbits around the Mercury poles.

"The cruise will be just over seven years old," said Ulrich Reininghaus, project manager at ESA. "We will fly over the Earth (once), twice Venus and six times Mercury itself before entering the orbit, allowing us to capture with the low gravity of the planet Mercury against the big sun.

"It means that when we fly, we constantly brake against the sun," he said. "When you fly to the heavier element (of the solar system), you are constantly accelerating. We do not want that. That's why we decelerate. "

The DFO satellite's orbit will have a low point of about 300 miles and a high point of about 930 miles. The JAXA MMO will orbit at a higher altitude, up to 7,200 miles above the surface.

Once in position, the spacecraft will have to withstand temperatures of up to 660 degrees at an average distance of 37 million miles from the Sun.

"Mercury is three times closer to the sun, so the radiation and heat we get from Mercury is 10 times higher," Benkhoff said. "So, everything … had to withstand the higher temperatures, but also the higher radiation doses we received from the solar wind. And for this, we need special insulation of our spaceship, special materials for the antenna, for solar panels. It was a very big challenge. "

Only two other spacecraft have already visited Mercury and only one of them has entered orbit.

The NASA Mariner 10 was the first spacecraft to make this trip. He flew over the planet three times in 1974 and 1975 and collected the first close-ups and other data at an altitude of up to 200 miles. Mariner 10 was also the first interplanetary spacecraft to use gravity-assisted overflights, a procedure that quickly became commonplace.

Launched in 2004, the NASA Messenger spacecraft was launched into Mercury in 2011 and spent four years studying the surface and space environment of the planet with a suite of sophisticated instruments. Although extremely fruitful, scientists still have important issues unresolved.

Enter BepiColombo, named after Giuseppe "Bepi" Colombo, mathematician and Italian engineer who discovered that Mercury was spinning on its axis three times for two orbits of the sun and suggested how gravity assistance could be used to reach the planet

ESA's Mercury Planetary Orbiter has 11 instruments, including cameras, spectrometers, a radiometer, a laser altimeter, a magnetometer and others, which will focus on the surface and the internal composition of the planet.

The JAXA Mercury Magnetospheric Orbiter is equipped with five instruments: a magnetometer, an ion spectrometer, an electronic energy analyzer, plasma detectors and a camera. It is designed to map the planet's magnetic field and its interactions with the sun.

Scientists hope to answer the following questions:

Mercury has a higher overall density than any other terrestrial world. Why?
Is the core of the planet at least partially liquid or solid?
-The planet is tectonically active?
– How does such a small planet maintain an intrinsic magnetic field and how does it interact with the solar wind?
Iron is probably the main constituent of mercury, but it is not seen in spectroscopic analysis. Why?
Do craters permanently shaded near the Mercury poles contain ice or sulfur reservoirs?
– What produces a thin "exosphere" around the planet?

"The study of Mercury is crucial to better understand the formation of our solar system, how the Earth has formed and evolved and where we have come from," said Benkhoff.

BepiColombo, he said, will help scientists "understand the nature of the planet".

"We want to characterize the surface, what materials are on the surface, we would like to measure temperatures, we would like to see the interaction with the solar wind, which is special about Mercury because it is so close to the sun," he said. . "Mercury has a magnetic field, which looks like Earth, a dynamo field. We would like to understand that. "

Once in orbit, BepiColombo's orbiters should collect data for one year, possibly with a one-year mission extension.