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| Titel |
Neutrons and gamma-rays spectroscopy of Mercury surface: global mapping from ESA MPO-BepiColombo spacecraft by MGNS instrument. |
| VerfasserIn |
A. S. Kozyrev, L. I. Gurvits, M. L. Litvak, A. A. Malakhov, M. I. Mokrousov, I. G. Mitrofanov, A. A. Rogozhin, A. B. Sanin, A. Owens, V. N. Schvetsov |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250027357
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| Zusammenfassung |
| For analyse chemistry composition of Mercury subsurface we will apply method of as-called
remote sensing of neutrons. This method can be use for study celestial body of Solar system
without thick atmospheres, like Moon, Mars, Phobos, Mercury etc. by the analysis of induced
nuclear gamma-rays and neutron emission. These gamma-rays and neutrons are produced by
energetic galactic cosmic rays colliding with nuclei of regolith within a 1-2 meter layer of
subsurface.
Mercury Planetary Orbiter of BepiColombo mission includes the nuclear instrument
MGNS (Mercury Gamma-rays and Neutrons Spectrometers), which consists of
gamma-rays spectrometer for detection of gamma-ray lines and neutron spectrometer for
measurement of the neutron leakage flux. To test know theoretical models of Mercury
composition, MGNS will provide the data for the set of gamma-ray lines, which are
necessary and sufficient to discriminate between the models. Neutron data are known
to be very sensitive for the presence of hydrogen within heavy soil-constituting
elements. Mapping measurements of epithermal neutrons and 2.2 MeV line will allow
us to study the content of hydrogen over the surface of Mercury and to test the
presence of water ice deposits in the cold traps of permanently shadowed polar
craters of this planet. There are also three natural radioactive elements, K, Th and U,
which contents in the soil of a celestial body characterizes the physical condition of
its formation in the proto-planetary cloud. The data from gamma-spectrometer
will allow to compare the origin of Mercury with evolution of Earth, Moon and
Mars.
Three sensors for thermal and epithermal neutrons are made with similar 3He
proportional counters, but have different polyethylene enclosures and cadmium shielding for
different sensitivity of thermal and epithermal neutrons at different energy ranges. The fourth
neutron sensor for high energy neutrons 1-10 MeV contains the scintillation crystal of
stylbene with cylindrical shape of size Ø30Ã40 cm. The gamma-rays spectrometer contains
scintillation crystal of LaBr3 for detection of gamma-ray photons with very high
spectral resolution of 3 % at 662 keV. The total mass of MGNS instrument is 5.2
kg; it consumes 4.0 W of power and provides about 9.0 Mb of telemetry data per
day.
At present, the nuclear instrument MGNS is under development for implementation on
the MPO of BepiColombo mission, as the contribution of Federal Space Agency of Russia to
this ESA project. In comparison of gamma-rays spectrometer onboard NASA’s Messenger
interplanetary probe, whitch will provide mapping data for northern hemisphere of the planet
only because of elliptical orbit, the MGNS onboard MPO will provide global mapping of the
planet with similar coverage of southern and northern hemispheres of the Mercury. |
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