BepiColombo: more about MORE
BepiColombo was successfully launched by an Ariane 5 rocket from Europe’s Spaceport in Kourou, French Guiana at 01:45 GMT on October 20, 2018. A joint mission by the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA), under ESA leadership, BepiColombo is the first European mission to Mercury, the smallest and least explored planet in the inner Solar System. The mission comprises two operational modules: the Mercury Planetary Orbiter (MPO) to map the planet and the Mercury Magnetospheric Orbiter (MMO) to investigate its magnetosphere, in addition to a transfer module that will propel the composite spacecraft to Mercury. The MPO’s payload comprises eleven instruments, including MORE (Mercury Orbiter Radio-Science Experiment), developed by Thales Alenia Space in conjunction with Sapienza University of Rome.
We asked Lorenzo Simone (Radio-Communication Products and TT&C Manager at Thales Alenia Space) to describe this experiment.
Lorenzo, what’s your role on this instrument, and what is it used for?
I am the designer of the Ka-band transponder for the Mercury Orbiter Radio-science Experiment. MORE is designed to measure the rotational state of Mercury and the overall structure of the gravity field, and also carry out an extensive series of tests on Einstein’s Theory of General Relativity by measuring the planet’s orbit around the Sun and the propagation of electromagnetic waves to and from the Earth.
How does it work?
MORE uses a Ka-band link that is coherently converted from 34 GHz (uplink) to 32 GHz (downlink). The uplink signal is also modulated by a wideband pseudo-noise (50 MHz bandwidth), which is fully demodulated onboard and then retransmitted to the ground by phase modulating the downlink carrier. The Ka-band transponder will allow us to estimate the distance between the Earth and the spacecraft (exceeding 200 million kilometers at its farthest point) to within a few centimeters, and the spacecraft’s radial velocity to within a few tenths of a micron per second.
More specifically, how will MORE help us study Mercury?
MORE will help determine the gravity field of Mercury, as well as the size and state of its core. It will provide crucial experimental feedback to develop models of the planet's internal structure and also test theories of gravity with unprecedented accuracy. It will measure solar gravitational oblateness and test and characterize the most advanced interplanetary tracking system ever built. In addition, it will assess the performance of the innovative tracking system for high-precision orbit determination and space navigation.
When we will receive initial feedback from the experiment?
After a cruise phase of 7 years, the MORE mission will start as soon as the spacecraft reaches orbit around Mercury. In the meantime, the transponder will be switched on from time to time to check its health.
En route to Mercury with Thales Alenia Space
This European mission is led by Airbus Defence & Space as prime contractor, working on behalf of ESA. Thales Alenia Space is part of the industry core team, coordinating 35 different European companies. In particular, Thales Alenia Space is in charge of telecommunications, thermal control and the electrical distribution system, as well as integration and testing of the overall spacecraft, plus support services during the launch campaign. The company is also supplying X and Ka-band transponders, onboard computers, mass memory and the 1.1 meter high-gain antenna used for communications between spacecraft and ground, along with the scientific experiment for the radio mission. This antenna is derived from the model developed for the successful Cassini-Huygens mission.
BepiColombo: ©ESA/ATG mediaLab - Mercury: ©NASA/JPL