Destination Mercury: Sapienza en route with the BepiColombo Probe
Mission BepiColombo is set to take off for Mercury from the Kourou Space Centre in FrenchGuyana at 3:45 am (Italian time) on the night between October 19 and 20. The probe will be launched with an Ariane 5 rocket, the most powerful available in Europe. This is the first European mission towards the planet that is closest to the Sun and the third such mission after NASA’s Mariner 10 Mission (1973) and Messenger Mission (2004). As such, it rightly stands out as a milestone for the European Space Agency (ESA).
The BepiColombo Mission has been made possible thanks to the collaboration between ESA and JAXA, the Japanese Space Agency. ESA developed the Mercury Planetary Orbiter (MPO) Module, while the Japanese Space Agency produced the Mercury Magnetospheric Orbiter (MMO). Both modules will be placed in orbit around Mercury in about seven years, after a series of passages near the Earth, Venus and Mercury, too.
The sophisticated on-board instruments will allow the mission to study the planet in great detail (internal structure, lithosphere, chemical composition) and the surrounding environment (solar wind and magnetic field). The analysis of the internal structure will provide information on the primordial cloud that gave birth to the solar system and the evolution of the planet over the last 4.6 billion years. Moreover, it will also provide useful information for the study of exoplanets, many of which orbit around the host start at a distance similar to that between Mercury and the Sun. Last, but not least, the measure of the gravity field will allow us to understand the geological evolution of the planet. “The BepiColombo Mission,” explains Prof. Iess, “thrusts Europe towards the exploration of Mercury, one of the most fascinating objects in our Solar System.”
Four out of the eleven scientific instruments on board the ESA probe are Italian. These include the Mercury Orbiter Radioscience Experiment (MORE) headed by Prof. Luciano Iess from the Sapienza Department of Mechanical and Aerospace Engineering together with an international team of scientists and engineers. In Italy, collaborators include the Universities of Pisa and Bologna and the Abruzzo Astronomical Observatory of the National Astrophysics Institute.
MORE includes two main elements: the KaT (Ka-band Transponder), funded by the Italian Space Agency (ASI) and developed by Thales Alenia Space Italy, and the two great antennas in the deserts of California and Malargue in Argentina. The exchange of radio signals between the antennas on earth and the KaT will allow us to measure the distance of the probe to a precision of a few centimetres and its velocity to a thousandth of a millimetre a second. This, in turn, will allow us to accurately determine the gravity and orbit of Mercury. Yet another Italian tool, the Italian Spring Accelerometer (ISA), will measure all forces acting on the probe (other than gravity) to make the measurements as precise as possible.
“The scientific objectives of MORE,” points out Luciano Iess, “do not only include the determination of Mercury’s internal structure with precise measurements of the planet’s gravity, but also the search for possible violations of Einstein’s Theory of General Relativity through the reconstruction - just a few centimetres off - of Mercury’s orbit.” In fact, Mercury is in a zone of the Solar System in which the curvature of time-space produced by the Sun (and predicted by Einstein’s Theory) is more marked. This curvature produces anomalies in the planet’s orbit that have been measured since the 19thcentury but were only explained in 1915 thanks to the Theory of General Relativity; indeed, the first experimental clue to it.
“Thanks to MORE,” adds Iess, “we will be able to accurately determine Mercury’s orbit, and this will allow us to verify more precisely than ever before if the Theory of General Relativity remains a valid theory for gravitation. And, of course, MORE is also a test of a new and advanced space navigation system.”
The BepiColombo Mission is dedicated to Italian scientistGiuseppe “Bepi” Colombo, who provided much impetus to the study and exploration of Mercury.
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Department of Mechanical and Aerospace Engineering, Sapienza University