Multilayers coatings for space and solar applications are usually exposed to harsh environments. Thermal stress, ion
bombardments and natural aging process can affect their performances over time. We have investigated the α–particles
stability of UV and EUV optical coatings suitable for high–performance solar instrumentation. Experimental procedures,
analysis and preliminary results are discussed hereafter.
The calibration of space instrumentations requires devoted tools to characterize optical subsystems and whole instruments. Then, new facilities in the Extreme and Near UltraViolet spectral regions have been developed and already used for the preliminary ground calibration activities of PHEBUS, the spectrometer that will flight onboard of BepiColombo mission.
The Multi Element Telescope for Imaging and Spectroscopy (METIS) coronagraph is an instrument belonging to the
SOLar Orbiter(SOLO) mission payload which will perform the imaging of the solar corona in three different spectral
ranges: 30.4 nm (He-II Lyman-α line), 121.6 nm (H-I Lyman- α line) and visible spectral range (500-650 nm). Optical
coatings with high reflectance performances at the interested wavelengths are required to collect enough light at the
detector level. Different multilayer structures based on Si/Mo couples with appropriate capping layers have been already
designed and tested to achieve this purpose. A model has been developed in order to estimate the efficiency's
performances of the instrument on the whole field of view (FoV) by considering the ray paths. The results shown have
been obtained taking into account of the experimental results on multilayers structures previously tested and the optical
design of the instrument.
Calibration of optical systems is a fundamental step in the development of a space instrumentation. We have built a new
cleanroom environment, divided in different areas characterized by a different level of contamination control. A vacuum
chamber (a tube of 80 cm diameter, and 2 m length), able to accommodate optical components as well as whole
instruments, is interfaced with a ISO6 area, allowing the handling of the instrumentation in a clean environment. The
vacuum system is dimensioned to reach 10<sup>-7</sup> mbar pressure in the chamber. Inside, a two axis platform allows the rotation
of the instrument with respect to the incident collimating beam, in order to test the response of the instrument to light
coming from different points of the field of view. A monochromator coupled with different sources provides radiation in
the 40-350 nm spectral range, while a parabolic mirror is used as a collimator. As source, different spectral lamps can be
used to generate emission lines, while a Xe lamp can be used to have continuum spectrum. An high brilliant hollow
cathode lamp has been fabricated by the group to generate extreme ultraviolet radiation. Different calibrated detectors
and other completing optical components are available.
Probing of Hermean Exosphere By Ultraviolet Spectroscopy (PHEBUS) is a spectrometer that will fly on board of the
BepiColombo mission to investigate the composition and dynamic of Mercury’s exosphere. Calibration of QM and FM
instrument are on going. An approach based on the Mueller Matrix formalism is adopted to determine the pure efficiency
of the instrument (PHEBUS). The results obtained show that this approach is a complete and versatile method to perform
the radiometric calibration of a space instrument.
The Bepi Colombo mission will explore the Mercury planet and its environment. Probing of Hermean Exosphere
By Ultraviolet Spectroscopy (PHEBUS) is one of the instruments of the payload. It is a double spectrometer for
Extreme Ultraviolet (EUV) and Far Ultraviolet (FUV) spectral regions devoted to the characterization of
Mercury's exosphere. In this work we will present the calibration philosophy that will be applied to the Flight
Model, and explain how a full instrument calibration can be derived from the wholly characterization of the
optical subsystems through the Mueller Matrix formalism. The experimental results concerning of PHEBUS
prototype optical subsystems are presented, which have been performed in the 55 - 315 nm range by using the
normal incidence reflectometer at LUXOR Laboratory (CNR - Institute for Photonics and Nanotechnology,