4.7 BepiColombo
BepiColombo is Europe’s first mission to Mercury, the innermost planet of the
Solar System. As the planetary cornerstone of ESA’s Cosmic Vision Programme,
BepiColombo is a joint project between ESA and the Japanese Aerospace Exploration
Agency (JAXA). The mission, a satellite ‘duo’ consisting of an orbiter for planetary
investigations and an orbiter for magnetospheric studies, will reach Mercury after a
6-year journey towards the inner Solar System, to make a comprehensive, detailed
study of the planet. BepiColombo will also contribute to the understanding of the
history and formation of the inner planets of the Solar System in general, including
the Earth.
The ‘Mercury Planetary Orbiter’ (MPO), built under ESA’s responsibility, will
study the surface and the internal composition of the planet at different wavelengths
and using different techniques. The MPO (Fig. 4.7.1) is 3-axis-stabilised and nadirpointing and will orbit the planet in a low eccentricity orbit: 400 x 1500 km. The
Mercury Magnetospheric Orbiter (MMO), built under the responsibility of JAXA,
will study the magnetosphere, which is the region of space around the planet that is
dominated by its magnetic field. The MMO (Fig. 4.7.2) is a spinning spacecraft and
its orbit is optimised for the given studies: 400 x 12 000 km.
ESA is responsible for the overall BepiColombo mission design, including
launcher, spacecraft composite, propulsion modules, ground segment and the
delivery of both spacecraft into their dedicated orbits, as well as for the MPO and
its operations. JAXA is responsible for the procurement of the MMO and for its
mission and science operation at Mercury. The mission scenario foresees a launch
of both spacecraft on a single Soyuz-Fregat 2-1B in August 2013 and an arrival at
Mercury in August 2019. The 6-year cruise phase is achieved using a combination
of seven flybys (the Moon, two of Venus, four of Mercury) and electric propulsion.
The launch configuration is a stack, consisting of the two spacecraft (MMO protected
from solar radiation by a sunshield) and the chemical and electrical propulsion
module MTM (see also Fig. 4.7.3).
Introduction
Figure 4.7.1: Mercury Planetary Orbiter
(Astrium GmbH, Germany)
For further information, see http://sci.esa.int/bepicolombo
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Figure 4.7.2: Mercury Magnetospheric
Orbiter (A. Luktus)
Figure 4.7.3: BepiColombo’s cruise
configuration, consisting of the Mercury
Transfer Module (MTM) providing the
chemical and electrical propulsion, the
two spacecraft MPO and MMO, and the
sunshield covering the MMO from solar
irradiation during the 6-year cruise phase.
Scientific objectives
Due to Mercury’s close proximity to the Sun, both spacecraft will have to
withstand extremely high temperatures and radiation doses, which necessitate the
inclusion of radiators and extensive shielding in their design. The MPO employs
lightweight technologies and materials able to cope with the aggressive thermal
environment at Mercury. The difficulty of reaching, surviving and operating in the
harsh environment of the planet makes BepiColombo one of the most challenging
long-term planetary projects attempted by ESA so far.
BepiColombo was named after Giuseppe (Bepi) Colombo (1920–1984), a scientist
who studied Mercury’s orbital motion in detail and greatly contributed to the study
of orbits and interplanetary travel. NASA’s Mariner 10 was the first spacecraft to
visit Mercury and provided many closeup images of the planet when it flew past
three times in 1974–1975. Recently NASA’s Messenger spacecraft (due to arrive in
an orbit around Mercury in 2011) took further closeup measurements during a flyby
manoeuvre performed in January 2008. Reaching the planet in 2019, BepiColombo
will be the second mission in the history of planetary exploration to orbit Mercury.
The current baseline is one Earth-year of science operations in Mercury orbit, with
the possibility to extend the mission for another year.
BepiColombo will study and contribute to the understanding of the composition,
geophysics, atmosphere, magnetosphere and evolution of Mercury, the innermost
planet in the Solar System. In particular, the mission objectives are to study:
— origin and evolution of a planet close to its parent star;
— Mercury’s form, interior structure and composition;
— interior dynamics and origin of its magnetic field;
— exogenic and endogenic surface modifications, cratering, tectonics, volcanism;
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— composition, origin and dynamics of Mercury’s exosphere and polar deposits;
— structure and dynamics of Mercury’s magnetosphere; and
— to test Einstein’s theory of general relativity.
The MPO will perform a global mapping of the surface morphology, composition
and temperature of Mercury, study its extremely thin atmosphere (exosphere) and
investigate its interior structure and magnetic field. The MMO will focus on the
investigation of the magnetic field, waves and particles in the environment of Mercury,
which will result in a complete characterisation of the planet’s magnetosphere. It will
also provide information on the exosphere to complement the MPO investigations
and determine the interplanetary dust environment around Mercury. Simultaneous
measurements by the two spacecraft will resolve spatial and temporal ambiguities in
the exosphere and magnetosphere that would arise from single-point observations.
For instance, parallel measurements of the magnetic flux by the magnetometers on
both spacecraft will enable separation of the contributions from the magnetosphere
and the planetary magnetic field.
BepiColombo MPO and MMO instruments were selected in November 2004, by
ESA and JAXA respectively.
The Mercury Magnetospheric Orbiter will carry five advanced scientific
experiments that will be provided by nationally funded Principal Investigators (PIs),
one European and four from Japan (Table 4.7.1).
The Mercury Planetary Orbiter will carry a highly-sophisticated suite of eleven
scientific instruments, ten of which will be provided by PIs through national funding
by ESA Member States, and one from Russia (Table 4.7.2).
MPO and MMO payload
Table 4.7.1. The MMO experiments.
Mercury Magnetometer (MERMAG-MGF)
Will provide a detailed description of Mercury’s magnetosphere and
of its interaction with the planetary magnetic field and the solar wind
(W.Baumjohann, Austrian Academy of Sciences, Austria).
Mercury Plasma Particle Experiment (MPPE)
Will study low- and high-energetic particles in the magnetosphere
(Y. Saito, ISAS, JAXA, Japan).
Mercury Plasma Wave Instrument (PWI)
Will make a detailed analysis of the structure and dynamics of the
magnetosphere (H. Matsumoto, RISH, Kyoto Univ., Japan).
Mercury Sodium Atmospheric Spectral Imager (MSASI)
Will measure the abundance, distribution and dynamics of sodium in
Mercury’s exosphere (I. Yoshikawa, Univ. Tokyo, Japan).
Mercury Dust Monitor (MDM)
Will study the distribution of interplanetary dust in the orbit of Mercury
(K.Nogami, Dokkyo Med. Univ., Japan).
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Table 4.7.2. The MPO instruments.
BepiColombo Laser Altimeter
(BELA)
Will characterise the topography and surface morphology of Mercury.
It will also provide a digital terrain model that, when compared with the
data from the radio science instrument, will impart information about
the internal structure, the geology, the tectonics, and the age of the
planet’s surface. (Principal Investigators: N. Thomas, University of Bern,
Switzerland, and T. Spohn, DLR, Germany).
The Mercury Magnetometer
(MERMAG-MAG)
Will provide measurements that will lead to the detailed description of
Mercury’s planetary magnetic field and its source, to better understand
the origin, evolution and current state of the planetary interior, as well
as the interaction between Mercury’s magnetosphere with the planet
itself and with the solar wind. (K.H. Glassmeier, Technical University of
Braunschweig, Germany).
Mercury Thermal Infrared Spectrometer
(MERTIS)
Will provide detailed information about the mineralogical composition
of Mercury’s surface layer with a high spectral resolution, crucial
for selecting the valid model for origin and evolution of the planet
(H. Hiesinger, University Münster, Germany).
Mercury Gamma ray and Neutron Spectrometer
(MGNS)
Will determine the elemental composition of the surface and subsurface
of Mercury, as well as the regional distribution of volatile depositions
in the polar areas, which are permanently shadowed from the Sun
(I. Mitrofanov, Institute for Space Research, Russia).
Mercury Imaging X ray Spectrometer
(MIXS)
Will use the ‘X ray fluorescence’ analysis method to produce a global
map of the surface atomic composition at high spatial resolution
(G. Fraser, University of Leicester, UK).
Mercury Orbiter Radio Science Experiment
(MORE)
Will help to determine the gravity field of Mercury, as well as the
size and physical state of its core. It will provide crucial experimental
constraints to models of the planet’s internal structure and test theories
of gravity with unprecedented accuracy (L. Iess, University of Rome “La
Sapienza”, Italy).
Italian Spring Accelerometer
(ISA)
The objectives are strongly connected with those of the MORE
experiment. Together the experiments can give information on Mercury’s
interior structure as well as test Einstein’s theory of the General Relativity
(V. Iafolla, CNR-IFSI, Italy).
Probing of Hermean Exosphere by Ultraviolet Spectroscopy
(PHEBUS)
Spectrometer is devoted to characterising the composition and dynamics
of Mercury’s exosphere. It will also search for surface ice layers in
permanently shadowed regions of high-latitude craters (E. Chassefière,
Université P&M Curie, France).
Search for Exosphere Refilling
and Emitted Neutral Abundances (SERENA)
Will study the gaseous interaction between surface, exosphere,
magnetosphere and solar wind (S. Orsini, CNR-IFSI, Italy).
Spectrometers and Imagers for MPO BepiColombo
Integrated Observatory System (SYMBIO-SYS)
Will examine the surface geology, volcanism, global tectonics, surface
age and composition, and geophysics (E. Flamini, ASI, Italy).
Solar Intensity X ray Spectrometer (SIXS)
Will perform measurements of X rays and particles of solar origin at high
time resolution and a very wide field of view (J. Huovelin, Observatory
University of Helsinki, Finland).
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