Geoscience Reference
In-Depth Information
necessary data in orbital phases of Mercury while the planet is behind the
Sun. Scientific objectives for SIXS are studies of temporal and spectral
variability of solar X-ray corona, temporal behavior, and X-ray spectral
classification of solar flares, and temporal and spectral variability of proton
and electron radiation near Mercury.
2.4.5.
Probing of hermean exosphere by ultraviolet spectroscopy
Probing of hermean exosphere by ultraviolet spectroscopy (PHEBUS) is
a dual ultra-violet spectrometer working in the wavelength range from 55
to 315 nm and devoted to characterize Mercury's exosphere composition
and dynamics. The search for surface ice layers in permanently shadowed
regions of high-latitude craters is one of the instrument objectives. However,
the general scientific objectives of PHEBUS, oriented toward better under-
standing the coupled surface exosphere-magnetosphere system are to detect
new species, including metallic ones, volatile atoms, molecules and radicals,
noble gases, and ions, in addition to already detected species; to measure
an average exosphere (number densities of constituents, vertical structure),
with as much as possible species monitored together, at different positions
of Mercury around the Sun; to measure sharp local and temporal varia-
tions of the exosphere content (time scale: less than a few hours), at specific
times and places of interest and to search for albedo variations of Mercury's
night side surface, lighted by the interplanetary H Ly-
α
glow in order to
exhibit possible signatures of surface ice layers (H
2
O, SO
2
,N
2
,CO
2
,
...
)
in high latitude polar craters, and any other signature of interest on the
night side.
2.4.6.
Search for exospheric refilling and emitted natural abundances
The scientific objectives of search for exospheric refilling and emitted natu-
ral abundances (SERENA) are to provide information on the whole surface-
exosphere magnetosphere system and the processes involved in the system
as well as in the interaction with the solar wind and the interstellar medium.
The interaction between the Hermean environment with energetic plasma
particles, solar radiation, and micrometeorites gives rise to both thermal
and directional neutral populations in the near-planet space. The SER-
ENA neutral particle analyser sensors will record such populations, while
the SERENA ion spectrometer sensors will record photo-ionized or charged
components of the surface release processes as well as the plasma precipi-
tation and circulation in the Hermean magnetosphere.
