Silvano Fineschi - Academia.edu (original) (raw)
Papers by Silvano Fineschi
Magnetic Fields Across the Hertzsprung Russell Diagram, 2001
X Ray and Ultraviolet Polarimetry, Feb 1, 1994
The paper deals with the mission analysis and conceptual design of an interplanetary 6U CubeSats ... more The paper deals with the mission analysis and conceptual design of an interplanetary 6U CubeSats system to be implemented in an Earth-Sun Lagrangian Points mission for solar observation and in-situ space weather measurements. Interplanetary CubeSats could be an interesting alternative to big missions, to fulfill both scientific and technological tasks in deep space, as proved by the growing interest in this kind of application in the scientific community and most of all at NASA. Such systems allow less costly missions, due to their reduced sizes and volumes, and consequently less demanding launches requirements. The CubeSats mission presented in this paper is aimed at supporting measurements of space weather. The mission envisages the deployment of a 6U CubeSats system in one of the Earth-Sun Lagrangian Points, where solar observations for in situ measurements of space weather to provide additional warning time to Earth can be carried out. The proposed mission is also intended as a technology validation mission, giving the chance to test advanced technologies, such as telecommunications and solar sails, envisaged as propulsion system. Furthermore, travelling outside the Van Allen belts, the 6U CubeSats system gives the opportunity to further investigate the space radiation environment: radiation dosimeters and advanced materials are envisaged to be implemented, in order to test their response to the harsh space environment, even in view of future implementation on other spacecrafts (e.g. manned spacecrafts). The main issue related to CubeSats is how to fit big science within a small package - namely power, mass, volume, and data limitations. One of the objectives of the work is therefore to identify and size the required subsystems and equipment, needed to accomplish specific mission objectives, and to investigate the most suitable configuration, in order to be compatible with the typical CubeSats (multi units) standards. The work has been developed as collaboration between Politecnico di Torino, University "La Sapienza" (Rome), "Osservatorio Astronomico di Torino - OATO" (Astronomical Observatory of Torino) and DLR (Deutsches Zentrum fur Luft- und Raumfahrt) in Bremen
ABSTRACT We present here comprehensive experimental data corresponding to helium extreme ultravio... more ABSTRACT We present here comprehensive experimental data corresponding to helium extreme ultraviolet emission (EUV) for the 300-600A wavelength range in e- + He, H+ + He, and Hnn+ + He (n=2-3) collisions with impact velocities ranging from 1.4 to 6.9 a.u. The degree of linear polarization associated with HeI (1snp) 1Po -> (1s2) 1S decays for n-2-5 ((lambda) =510 to 584A) and HeII (2p) 2Po -> (1s) 2S transitions ((lambda) =304A), have been measured at intermediate and higher energies. These measurements have been conducted using a compact lightweight molybdenum/silicon multilayer mirror (MLM) spetropolarimeter. These experimental results are compared with our most advanced theoretical calculations using the close coupling method and several many body perturbation approaches. In this study, the degree of linear polarization will be discussed as a function of the projectile charge to elucidate few body excitation and ionization-excitation processes. Specifically, more sophisticated calculations including second Born approximation with full off-energy terms for the HeII (2p) 2Po sublevels have been used. The excellent agreement with our HeII Lyman-(alpha) data clearly demonstrates that off-energy terms in two-electron atomic interaction have very prominent effects. Our comprehensive experimental and theoretical database is also of great importance for the understanding of solar physics phenomena. Such results can be used as a new diagnostic tool for clarifying the role of electron and proton beams in solar flares.
Good theoretical designs of far ultraviolet polarizers have been reported using a MgF2/AI/MgF 2 t... more Good theoretical designs of far ultraviolet polarizers have been reported using a MgF2/AI/MgF 2 three layer structure on a thick Ai layer as a substrate. The thicknesses were determined to induce transmission and absorption of p-polarized light. In these designs AI optical constants were used from films produced in ultrahigh vacuum (UHV: 10"10 tort). Reflectance values for polarizers fabricated in a conventional high vacuum (p--10 -6 torr) using the UHV design parameters differed dramatically from the design predictions. AI is a highly reactive material and is oxidized even in a high vacuum chamber. In order to solve the problem other metals have been studied. It is found that a larger reflectance difference is closely related to higher amplitude and larger phase difference of Fresnel reflection coefficients between two polarizations at the boundary of MgF2/metal. It is also found that for one material a larger angle of incidence from the surface normal brings larger amplitude and phase difference. Be and Mo are found good materials to replace A1. Polarizers designed for 121.6 run with Be at 600 and with Mo at 70 ° are shown as examples.
The Astrophysical Journal, 1992
Journal of Mathematical Physics, 1990
The property of the associated Legendre functions with non-negative integer indices, Pmn(z), desc... more The property of the associated Legendre functions with non-negative integer indices, Pmn(z), described by the formula: Pmn (cos β)=(−1)m(a/c)n ∑n−mk=0 (n+mk) (−b/a)n−k ×Pmn−k(cos γ), where a,b,c are the sides of an assigned triangle and α,β,γ the respective opposite angles, is introduced. A useful application of this series in simplifying the calculation of collisional electron–atom cross sections higher than the dipole is mentioned. A proof of the stated identity by use of the Gegenbauer polynomials and of their generating function is given.
Forest Ecology and Management, 2004
Optical Engineering, 1991
Several mechanisms can induce a detectable amount of linear polarization (≥l%) in spectral lines ... more Several mechanisms can induce a detectable amount of linear polarization (≥l%) in spectral lines emitted by the outer solar atmosphere at EUV/FUV wavelengths (ie, 100 Å ≤ λ.
Proceedings of Spie the International Society For Optical Engineering, Feb 1, 2003
UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XX, 2017
PROBA-3 [1] [2] is a Mission of the European Space Agency (ESA) composed by two satellites flying... more PROBA-3 [1] [2] is a Mission of the European Space Agency (ESA) composed by two satellites flying in formation and aimed at achieving unprecedented performance in terms of relative positioning. The mission purpose is, in first place, technological: the repeated formation break and acquisition during each orbit (every about twenty hours) will be useful to demonstrate the efficacy of the closed-loop control system in keeping the formation-flying (FF) and attitude (i.e. the alignment with respect to the Sun) of the system. From the scientific side, instead, the two spacecraft will create a giant instrument about 150 m long: an externally occulted coronagraph named ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun) dedicated to the study of the inner part of the visible solar corona. The two satellites composing the mission are: the Coronagraph Spacecraft (CSC), hosting the Coronagraph Instrument (CI), and the disk-shaped (1.4 m diameter) Occulter Spacecraft (OSC). The PROBA-3 GNC (Guidance, Navigation and Control) system will employ several metrological subsystems to keep and retain the desired relative position and the absolute attitude (i.e. with respect to the Sun) of the aligned spacecraft, when in observational mode. The SPS subsystem [5] is one of these metrological instruments. It is composed of eight silicon photomultipliers (SiPMs), sensors operated in photovoltaic mode [6] that will sense the penumbra light around the Instrument’s pupil so to detect any FF displacement from the nominal position. In proximity of the CDR (Critical Design Review) phase, we describe in the present paper the changes occurred to design in the last year in consequence of the tests performed on the SPS Breadboard (Evaluation Board, EB) and the SPS Development Model (DM) and that will finally lead to the realization of the flight version of the SPS system.
UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XX, 2017
PROBA3/ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Coron... more PROBA3/ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun) is the first formation flight solar coronagraph, scheduled by ESA for a launch and currently in phase C/D. It is constituted by two spacecraft (one hosting the occulter, diameter 142 cm, and one with the telescope) separated by 144 m, kept in strict alignment by means of complex active and metrology custom systems. The stray light analysis, which is always one the most critical work packages for a solar coronagraph, has been only theoretically investigated so far due to the difficulty of replicating the actual size system in a clean laboratory environment. The light diffracted by the external occulter is the worst offender for the stray light level on the instrument focal plane, thus there is strong interest for scaling at least the occultation system of the coronagraph and test it in front of a solar simulator in order to experimentally validate the expected theoretical performance. The theory for scaling the occulter, the occulter-pupil distance and the source dimension has been developed and a scaled model is being manufactured. A test campaign is going to be conducted at the OPSys facility in Torino in front of a solar simulator (conveniently scaled). This work accounts for the description of the scaled model laboratory set-up and of the test plan.
2019 IEEE 5th International Workshop on Metrology for AeroSpace (MetroAeroSpace), 2019
The PROBA-3 is a European Space Agency (ESA) mission devoted to obtain, as never before, highly a... more The PROBA-3 is a European Space Agency (ESA) mission devoted to obtain, as never before, highly accurate formation flying. A couple of satellites will works together as an externally occulted solar coronagraph. The distance between the two satellites is of 144 meters and the required longitudinal accuracy of the relative positioning is better than 1 mm. In this proceeding the in-flight calibration of one of the most accurate metrology subsystem, the SPS (Shadow Position Sensors), will be presented.
UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XX, 2017
The paper describes the wavefront error measurements of the concave ellipsoidal mirrors M1 and M2... more The paper describes the wavefront error measurements of the concave ellipsoidal mirrors M1 and M2, of the concave spherical mirror M0 and of the flat interferential filter IF of the Metis coronagraph. Metis is an inverted occultation coronagraph on board of the ESA Solar Orbiter mission providing a broad-band imaging of the full corona in linearly polarized visible-light (580 - 640 nm) and a narrow-band imaging of the full corona in the ultraviolet Lyman α (121.6 nm). Metis will observe the solar outer atmosphere from a close distance to the Sun as 0.28 A.U. and from up to 35deg out-of-ecliptic. The measurements of wavefront error of the mirrors and of the interferential filter of Metis have been performed in a ISO5 clean room both at component level and at assembly level minimizing, during the integration, the stress introduced by the mechanical hardware. The wavefront error measurements have been performed with a digital interferometer for mirrors M0, M1 and M2 and with a Shack-Hartmann wavefront sensor for the interferential filter.
Magnetic Fields Across the Hertzsprung Russell Diagram, 2001
X Ray and Ultraviolet Polarimetry, Feb 1, 1994
The paper deals with the mission analysis and conceptual design of an interplanetary 6U CubeSats ... more The paper deals with the mission analysis and conceptual design of an interplanetary 6U CubeSats system to be implemented in an Earth-Sun Lagrangian Points mission for solar observation and in-situ space weather measurements. Interplanetary CubeSats could be an interesting alternative to big missions, to fulfill both scientific and technological tasks in deep space, as proved by the growing interest in this kind of application in the scientific community and most of all at NASA. Such systems allow less costly missions, due to their reduced sizes and volumes, and consequently less demanding launches requirements. The CubeSats mission presented in this paper is aimed at supporting measurements of space weather. The mission envisages the deployment of a 6U CubeSats system in one of the Earth-Sun Lagrangian Points, where solar observations for in situ measurements of space weather to provide additional warning time to Earth can be carried out. The proposed mission is also intended as a technology validation mission, giving the chance to test advanced technologies, such as telecommunications and solar sails, envisaged as propulsion system. Furthermore, travelling outside the Van Allen belts, the 6U CubeSats system gives the opportunity to further investigate the space radiation environment: radiation dosimeters and advanced materials are envisaged to be implemented, in order to test their response to the harsh space environment, even in view of future implementation on other spacecrafts (e.g. manned spacecrafts). The main issue related to CubeSats is how to fit big science within a small package - namely power, mass, volume, and data limitations. One of the objectives of the work is therefore to identify and size the required subsystems and equipment, needed to accomplish specific mission objectives, and to investigate the most suitable configuration, in order to be compatible with the typical CubeSats (multi units) standards. The work has been developed as collaboration between Politecnico di Torino, University "La Sapienza" (Rome), "Osservatorio Astronomico di Torino - OATO" (Astronomical Observatory of Torino) and DLR (Deutsches Zentrum fur Luft- und Raumfahrt) in Bremen
ABSTRACT We present here comprehensive experimental data corresponding to helium extreme ultravio... more ABSTRACT We present here comprehensive experimental data corresponding to helium extreme ultraviolet emission (EUV) for the 300-600A wavelength range in e- + He, H+ + He, and Hnn+ + He (n=2-3) collisions with impact velocities ranging from 1.4 to 6.9 a.u. The degree of linear polarization associated with HeI (1snp) 1Po -> (1s2) 1S decays for n-2-5 ((lambda) =510 to 584A) and HeII (2p) 2Po -> (1s) 2S transitions ((lambda) =304A), have been measured at intermediate and higher energies. These measurements have been conducted using a compact lightweight molybdenum/silicon multilayer mirror (MLM) spetropolarimeter. These experimental results are compared with our most advanced theoretical calculations using the close coupling method and several many body perturbation approaches. In this study, the degree of linear polarization will be discussed as a function of the projectile charge to elucidate few body excitation and ionization-excitation processes. Specifically, more sophisticated calculations including second Born approximation with full off-energy terms for the HeII (2p) 2Po sublevels have been used. The excellent agreement with our HeII Lyman-(alpha) data clearly demonstrates that off-energy terms in two-electron atomic interaction have very prominent effects. Our comprehensive experimental and theoretical database is also of great importance for the understanding of solar physics phenomena. Such results can be used as a new diagnostic tool for clarifying the role of electron and proton beams in solar flares.
Good theoretical designs of far ultraviolet polarizers have been reported using a MgF2/AI/MgF 2 t... more Good theoretical designs of far ultraviolet polarizers have been reported using a MgF2/AI/MgF 2 three layer structure on a thick Ai layer as a substrate. The thicknesses were determined to induce transmission and absorption of p-polarized light. In these designs AI optical constants were used from films produced in ultrahigh vacuum (UHV: 10"10 tort). Reflectance values for polarizers fabricated in a conventional high vacuum (p--10 -6 torr) using the UHV design parameters differed dramatically from the design predictions. AI is a highly reactive material and is oxidized even in a high vacuum chamber. In order to solve the problem other metals have been studied. It is found that a larger reflectance difference is closely related to higher amplitude and larger phase difference of Fresnel reflection coefficients between two polarizations at the boundary of MgF2/metal. It is also found that for one material a larger angle of incidence from the surface normal brings larger amplitude and phase difference. Be and Mo are found good materials to replace A1. Polarizers designed for 121.6 run with Be at 600 and with Mo at 70 ° are shown as examples.
The Astrophysical Journal, 1992
Journal of Mathematical Physics, 1990
The property of the associated Legendre functions with non-negative integer indices, Pmn(z), desc... more The property of the associated Legendre functions with non-negative integer indices, Pmn(z), described by the formula: Pmn (cos β)=(−1)m(a/c)n ∑n−mk=0 (n+mk) (−b/a)n−k ×Pmn−k(cos γ), where a,b,c are the sides of an assigned triangle and α,β,γ the respective opposite angles, is introduced. A useful application of this series in simplifying the calculation of collisional electron–atom cross sections higher than the dipole is mentioned. A proof of the stated identity by use of the Gegenbauer polynomials and of their generating function is given.
Forest Ecology and Management, 2004
Optical Engineering, 1991
Several mechanisms can induce a detectable amount of linear polarization (≥l%) in spectral lines ... more Several mechanisms can induce a detectable amount of linear polarization (≥l%) in spectral lines emitted by the outer solar atmosphere at EUV/FUV wavelengths (ie, 100 Å ≤ λ.
Proceedings of Spie the International Society For Optical Engineering, Feb 1, 2003
UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XX, 2017
PROBA-3 [1] [2] is a Mission of the European Space Agency (ESA) composed by two satellites flying... more PROBA-3 [1] [2] is a Mission of the European Space Agency (ESA) composed by two satellites flying in formation and aimed at achieving unprecedented performance in terms of relative positioning. The mission purpose is, in first place, technological: the repeated formation break and acquisition during each orbit (every about twenty hours) will be useful to demonstrate the efficacy of the closed-loop control system in keeping the formation-flying (FF) and attitude (i.e. the alignment with respect to the Sun) of the system. From the scientific side, instead, the two spacecraft will create a giant instrument about 150 m long: an externally occulted coronagraph named ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun) dedicated to the study of the inner part of the visible solar corona. The two satellites composing the mission are: the Coronagraph Spacecraft (CSC), hosting the Coronagraph Instrument (CI), and the disk-shaped (1.4 m diameter) Occulter Spacecraft (OSC). The PROBA-3 GNC (Guidance, Navigation and Control) system will employ several metrological subsystems to keep and retain the desired relative position and the absolute attitude (i.e. with respect to the Sun) of the aligned spacecraft, when in observational mode. The SPS subsystem [5] is one of these metrological instruments. It is composed of eight silicon photomultipliers (SiPMs), sensors operated in photovoltaic mode [6] that will sense the penumbra light around the Instrument’s pupil so to detect any FF displacement from the nominal position. In proximity of the CDR (Critical Design Review) phase, we describe in the present paper the changes occurred to design in the last year in consequence of the tests performed on the SPS Breadboard (Evaluation Board, EB) and the SPS Development Model (DM) and that will finally lead to the realization of the flight version of the SPS system.
UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XX, 2017
PROBA3/ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Coron... more PROBA3/ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun) is the first formation flight solar coronagraph, scheduled by ESA for a launch and currently in phase C/D. It is constituted by two spacecraft (one hosting the occulter, diameter 142 cm, and one with the telescope) separated by 144 m, kept in strict alignment by means of complex active and metrology custom systems. The stray light analysis, which is always one the most critical work packages for a solar coronagraph, has been only theoretically investigated so far due to the difficulty of replicating the actual size system in a clean laboratory environment. The light diffracted by the external occulter is the worst offender for the stray light level on the instrument focal plane, thus there is strong interest for scaling at least the occultation system of the coronagraph and test it in front of a solar simulator in order to experimentally validate the expected theoretical performance. The theory for scaling the occulter, the occulter-pupil distance and the source dimension has been developed and a scaled model is being manufactured. A test campaign is going to be conducted at the OPSys facility in Torino in front of a solar simulator (conveniently scaled). This work accounts for the description of the scaled model laboratory set-up and of the test plan.
2019 IEEE 5th International Workshop on Metrology for AeroSpace (MetroAeroSpace), 2019
The PROBA-3 is a European Space Agency (ESA) mission devoted to obtain, as never before, highly a... more The PROBA-3 is a European Space Agency (ESA) mission devoted to obtain, as never before, highly accurate formation flying. A couple of satellites will works together as an externally occulted solar coronagraph. The distance between the two satellites is of 144 meters and the required longitudinal accuracy of the relative positioning is better than 1 mm. In this proceeding the in-flight calibration of one of the most accurate metrology subsystem, the SPS (Shadow Position Sensors), will be presented.
UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XX, 2017
The paper describes the wavefront error measurements of the concave ellipsoidal mirrors M1 and M2... more The paper describes the wavefront error measurements of the concave ellipsoidal mirrors M1 and M2, of the concave spherical mirror M0 and of the flat interferential filter IF of the Metis coronagraph. Metis is an inverted occultation coronagraph on board of the ESA Solar Orbiter mission providing a broad-band imaging of the full corona in linearly polarized visible-light (580 - 640 nm) and a narrow-band imaging of the full corona in the ultraviolet Lyman α (121.6 nm). Metis will observe the solar outer atmosphere from a close distance to the Sun as 0.28 A.U. and from up to 35deg out-of-ecliptic. The measurements of wavefront error of the mirrors and of the interferential filter of Metis have been performed in a ISO5 clean room both at component level and at assembly level minimizing, during the integration, the stress introduced by the mechanical hardware. The wavefront error measurements have been performed with a digital interferometer for mirrors M0, M1 and M2 and with a Shack-Hartmann wavefront sensor for the interferential filter.