22.11.2019 10:00
BepiColombo Probe to Mercury. The history of a Politecnico constellation
Alumnus Gianluca Aranci recounts the story of this technological challenge, which began at Poli with a start-up in the 1950s
Right now, the BepiColombo probe is 42.4 million km from Earth and 135.5 million km from the Sun. In its current position, a command sent from the Earth takes 141 seconds to arrive (when the probe arrives at its final destination, this time will be much longer). The probe is on a smooth course, traveling at cruising speed; the scientific instrumentation is turned off and electric propulsion is activated. It has only completed a small part of its very long journey: it will still fly over Earth, Venus and on December 5, 2025 it is scheduled to arrive and enter the orbit around Mercury. At the end of its mission in 2028, it will have concluded in-depth studies on several aspects of the planet.
Alumnus Gianluca Aranci, the Head of Computer Products at Thales Alenia Space in Italy, the company that invented, designed and built the three onboard computers that are guiding and managing the probe, explains:
The mission is dedicated to the complete exploration of the planet and its environment. It is focused on understanding how a celestial body can evolve in the hottest part of the solar nebula; the mission will also study the magnetosphere, with comparative studies to that on Earth.
The technological challenge was how to build a space module equipped with extensive scientific instrumentation and a hull that could resist 430 degrees centigrade. “The extreme vicinity of the Sun,” continues Aranci, “generates the presence of a high-intensity gravitational field, to allow making specific measurements to confirm Einstein’s Theory of General Relativity. The ISA instrument will contribute to taking this measurement, which Thales Alenia Space helped to build. The instrument discriminates non-gravitational elements in the measurement of accelerations.”
Aranci and his team started working on the project in 2008. “The On Board Computer that we created manages platform data, and must provide very rapid identification of any faults or errors that could occur on the satellite, and based on the level hierarchy it must also rapidly intervene to resolve the problem. It is impossible to do so from earth, in particular in light of that fact that when the probe is orbiting Mercury communications will require 7 minutes to receive a signal and another 7 to transmit a command. In addition, there are long periods when we cannot see the satellite, therefore the computer must act on our behalf: from restarting software to electronically replacing certain parts. Let’s just say that the most interesting adventure of my middle age has begun.”
All of this work is characterized by another deeply-rooted Politecnico origin, in addition to that of Alumnus Aranci. This point of origin is namely Emilio Gatti, longtime professor at the Politecnico and a pioneer in electronic instrumentation for atomic and nuclear physics.
Emilio Gatti had a mind that was attentive to details, to finding the roots of things, and he knew how to transmit this to students. I thank my past at Politecnico for the opportunity to meet him, where I had the honor of attending his course in Applied Electronics in 1986.
History has it that many years prior, in 1958, on via Bassini, just across the road from the Politecnico, Gatti co-founded LABEN, a small company that produced sophisticated electronic instrumentation to support nuclear research. “Today we would call it a startup. It was one of the very first attempts to found a company based on the industrial need for laboratories, which at the time were studying nuclear energy.” Over the years, LABEN changed its name and ownership, and entered the aerospace sector. In 2013 the company moved and encountered Aranci: In Gorgonzola, in the Milan Province, incorporating to become Thales Alenia Space.
Today, this is still a creative space for many engineers from Poli: electronic, nuclear, aerospace and mechanical. We could say that it is made of minds from the Politecnico. We try to go beyond simple daily work, giving what we do a wider sense; it is nice to think that we contribute to a better world.
“Going to Mercury is not any easy thing,” explains Aranci, “and for the time being only United States has made it with the Mariner 10 in the 1970s and Messenger in the first decade of the 2000s. With BepiColombo, Europe will demonstrates its ability to handle very difficult tasks, also reaching Mercury using an electronic propulsion system.”
The computer from one of the four Cluster satellites found in a swamp in French Guiana after the first launch of the failed Ariane 5 missile in 1996 is exhibited in a display case. Something new is always born of failure. “The trajectory travelled by BepiColombo is an amazing feat all on its own,” he says, “only brilliant minds could conceive of and invent a way to send an artificial satellite in orbit around Mercury. If we look at the pathway that BepiColombo will travel throughout the whole solar system, we cannot help but be fascinated. Taking advantage of the gravitational attraction of Earth, Venus and Mercury, combatting immense attraction from the Sun, the probe will arrive bit by bit, “delicately” caressing the small planet, entering into its orbit. A voyage spanning seven years in darkness and silence, with the breathtaking views of the Sun and planets revolving around it; a solitary voyage, given that communications with stations on Earth require hundreds of seconds to transfer a message; a dangerous voyage, where at any moment something unexpected could go wrong, problems that our machines must be able to automatically correct if need be. But these are all risks that we are willing to face.”
I often think about Kennedy’s words, when he spoke about the motivation behind sending a man to the moon. He said “We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard.” This idea gives us courage and strength, because it demonstrates how humans, when they apply themselves with commitment, can do difficult, beautiful things.