ELENA instrument science and testing: validation with particle beam

Understanding of particle emission processes from the Mercury surface is one of the major objectives of ELENAinstrument in the SERENA experiment on board of the BepiColombo mission. In particular the Ion-Sputteringprocess resulting from charged and energetic particles impacting on the surface can be investigated detectingthe low energetic neutral particles escaping from the planet. The possibility to identify the Ion-Sputtering signaltogether with back-scattered particles and neutrals generated by charge exchange is strictly linked with the newtechnology capability to measure low energetic neutral atoms. This goal can be addressed thanks to a new&oldapproach for the neutral atoms measurement: a well known Time of Flight system enhanced with a new kind ofStart section able to define the start time of the entrance in the ToF path without interacting with the particles anddirectly follow to the Stop detector. The Start section is a shutter composed by two membranes with nanometricslits realized in a large area (1cm2) and oscillating at several frequencies to open and close the entrance of ToFsection. This system is never used before in space mission.The IFSI-INAF Ion beam facility in Rome is devoted to the ELENA testing. The crucial point of the shutteringsystem interaction with particle beam is investigated. The first results demonstrate the good functionality of thiskind of system: capability of the shutter to Open and Close the entrance respect to an ion beam is tested with aMCP stop detector. In this poster we present the IFSI activity in the frame of ELENA science requirement togetherwith the experimental activity devoted to instrument verification

The Future of Hyperspectral Imaging

The Special Issue on hyperspectral imaging (HSI), entitled “The Future of Hyperspectral Imaging”, has published 12 papers. Nine papers are related to specific current research and three more are review contributions: In both cases, the request is to propose those methods or instruments so as to show the future trends of HSI. Some contributions also update specific methodological or mathematical tools. In particular, the review papers address deep learning methods for HSI analysis, while HSI data compression is reviewed by using liquid crystals spectral multiplexing as well as DMD-based Raman spectroscopy. Specific topics explored by using data obtained by HSI include alert on the sprouting of potato tubers, the investigation on the stability of painting samples, the prediction of healing diabetic foot ulcers, and age determination of blood-stained fingerprints. Papers showing advances on more general topics include video approach for HSI dynamic scenes, localization of plant diseases, new methods for the lossless compression of HSI data, the fusing of multiple multiband images, and mixed modes of laser HSI imaging for sorting and quality controls

Phase and Index of Refraction Imaging by Hyperspectral Reflectance Confocal Microscopy

A hyperspectral reflectance confocal microscope (HSCM) was realized by CNR-ISC (Consiglio Nazionale delle Ricerche-Istituto dei Sistemi Complessi) a few years ago. The instrument and data have been already presented and discussed. The main activity of this HSCM has been within biology, and reflectance data have shown good matching between spectral signatures and the nature or evolution on many types of cells. Such a relationship has been demonstrated mainly with statistical tools like Principal Component Analysis (PCA), or similar concepts, which represent a very common approach for hyperspectral imaging. However, the point is that reflectance data contains much more useful information and, moreover, there is an obvious interest to go from reflectance, bound to the single experiment, to reflectivity, or other physical quantities, related to the sample alone. To accomplish this aim, we can follow well-established analyses and methods used in reflectance spectroscopy. Therefore, we show methods of calculations for index of refraction n, extinction coefficient k and local thicknesses of frequency starting from phase images by fast Kramers-Kronig (KK) algorithms and the Abeles matrix formalism. Details, limitations and problems of the presented calculations as well as alternative procedures are given for an example of HSCM images of red blood cells (RBC)

Dielectric properties of the Si(111)2×1 surface: Optical constants and the energy-loss spectrum

We present a method of computation of the optical constants of the surface layer of a solid, starting from a differential reflectivity spectrum. The differential reflectivity was obtained by comparing the overall reflectivity of the same sample in the case of a clean and oxidized surface. The method assumes sharp interfaces at the vacuum surface and at the surface bulk side. The physical properties of the bulk and of the surface layer are described by an energy-dependent dielectric constant. This method is applied to the Si(111)2×1 surface. The surface optical constants are derived in the (0.3-4.0)-eV range. With the use of the same model and the calculated optical constants, the electron-energy-loss spectrum of the Si(111)2×1 surface has been calculated. The agreement with the experiment is good. This is assumed as a proof of the reliability of the optical constants. In addition the comparison of the calculated energy-loss spectrum and the experiment allows the explanation of the apparent disagreement between optical and energy-loss experimental data in the near-infrared range. We demonstrate the different nature between the energy-loss peak and the optical one, the first due to the excitation of the two surface interface modes of the Si(111)2×1 surface layer and the second to an interband transition

Supercontinuum ultra wide range confocal microscope for reflectance spectroscopy of living matter and material science surfaces

We report the design and implementation of a new reflectance laser scanning confocal system with spectroscopy imaging capabilities. Confocal spectroscopy is achieved by using a very broad spectral range supercontinuum source capable of high precision reflectance data in the VIS-IR spectral range thanks to an almost achromatic optical layout. With this apparatus we collect each single scanning point as a whole spectrum in a continuous range, associated with the optical section imaging possibilities typical of a confocal set up. While such a microscope has been developed for bio medical analysis of human skin and other similar applications, first test results on solid samples produce spectroscopic results that, compared to analytical models based on the Abelés matrix transfer methods, show a very good agreement, opening new possibilities of a complete spectroscopic fingerprinting of samples with microscopic details

ELENA geometrical factor estimation

Here we calculate the geometrical factor for the ELENA instrument. ELENA (Emitted Low-Energy Neutral Atoms) is a neutral sensor, part of the SERENA instrument package, for the ESA cornerstone BepiColombo mission to Mercury; it is a new kind of low energetic neutral atoms instrument. It is designed to measure the sputtering emission from planetary surface in the energy range from E ~50eV up to E~5 keV. The instrument FoV is 4.5° by 76°, with nominal resolution of 4.5° by 2°, and nadir pointing. ELENA is a Time-of-Flight (ToF) sensor, based on oscillating shutter (operated at frequencies up to a 100 kHz) and mechanical gratings. The incoming neutral particles directly impinge on the entrance with a definite timing (START) and arrive to a STOP detector at the end of a Time-of-Flight (ToF) chamber. This paper describes both the analytical and the numerical estimation of the geometrical factor for the ELENA sensor. We obtain a geometrical factor of 1.5 10-3 cm2 sr, an angular resolution of 6.5° and a time resolution of 1.5 μs