Graduate School in Physics and Astrophysics ------------------------------------------- ANNUAL REPORT ------------------------------------------- Fill with a text editor (without TAB or formatting) Repeat fields for each course as necessary. ------------------------------------------- name: Marta Casti email: martacasti2190@gmail.com / marta.casti@unito.it ciclo: XXXI year completed (1,2 or 3): 2 supervisor: Silvano Fineschi, Nicole Viola ------------------------------------------- GRADUATE SCHOOL COURSES (only completed courses, with examination passed in the year) - ------------------------------------------- UNDERGRADUATE COURSES (Laurea Magistrale) (only completed courses, with examination passed in the year) - ------------------------------------------- SUMMER SCHOOLS, INTERNATIONAL SCHOOLS (only those attended in the current year) title: VarSITI 2017_Space Weather Summer School School place: Irkutsk, Russia webpage: http://varsiti2017.iszf.irk.ru/index.php/conferences/varsiti days: July 10-15, 2017 talk or poster (Y/N): Y(poster) ------------------------------------------- CONFERENCES, WORKSHOP (only those attended in the current year) title: 2017 IEEE International Instrumentation and Measurement Technology Conference (I2MTC) Conference place: Turin, Italy webpage: http://2017.imtc.ieee-ims.org/ days: May 22-25, 2017 talk or poster (Y/N): Y (talk) title: Space Weather: A Multi-Disciplinary Approach Workshop place: Leiden, The Netherlands webpage: http://lorentzcenter.nl/lc/web/2017/921/info.php3?wsid=921&venue=Oort days: September 25-29, 2017 talk or poster (Y/N): N --------------------------------------------------- Research activity/Publications in the current year During the second year of my PhD I continued the research activity started last year. The focus was on the two main subjects of my PhD research: 1. Calibration of the polarimeter for the Metis coronagraph on Solar Orbiter. The Metis Solar coronagraph was selected by the European Space Agency to be part of the payload of the Solar Orbiter mission. Metis will observe the linearly polarized visible-light emission from the K-corona for the determination of the coronal electron density. This year, my PhD activity focused on the calibration of the proto-flight model of the Metis polarimeter. All the optical elements of the polarimeter have been characterized at the component-level. Then the polarimeter has been assembled and calibrated at the system. Finally, the instrument has been integrated in the coronagraph and a calibration campaign was performed both, in air and in vacuum, on the whole Metis instrument. On October 2016, I took part to the calibration of the proto-flight model of the Metis polarimeter at Optec, the optics company responsible for the integration. The Metis polarimeter is composed of two identical Liquid Crystal Variable Retarders (LCVRs) (i.e., the Polarization Modulation Package (PMP)), a linear polarizer and a quarter wave retarder. The calibration activities were performed on the individual components and on the final assembly. In particular, in order to calibrate the PMP we acquired data for different values of voltage applied to the LCVR cells. With these data, it was possible to study and characterize the electro-optical modulation of the incoming polarized light induced by the liquid crystals molecules inside the LCVRs. The response of the molecules inside the cells change with the temperature. Therefore, the calibration of the PMP included the acquisition of calibration data at different operational temperatures. At the same time, the linear polarizer and the quarter wave retarder were calibrated in order to verify their optical performances, in particular, to determine the error on the orientation of the acceptance and the fast axis of the quarter-wave retarder and the linear polarizer, respectively. Once these data had been acquired, the Metis polarimeter was assembled and the calibration of the whole polarimeter was carried out. The goal of this calibration campaign was to fully characterize the optical performances of the polarimeter considering different operational conditions. The output of the analysis of these data were: the retardance vs voltages of the PMP and the modulation and demodulation matrices associated with the Metis polarimeter. In addition, the collected data and their analysis were useful for the next step: the analysis and the verification of the polarimeter response after its integration in the coronagraph. From March until May 2017, the Metis coronagraph was integrated and calibrated in the INAF-Optical Payload System (OPSys) facility, hosted in ALTEC S.p.A., Torino, the industry where my PhD apprenticeship takes place. In that period, we acquired data to characterize the optical response of the polarimeter, which had been integrated in the visible channel of the instrument. Data related to the polarimeter response were collected both, in air and in vacuum condition. Once all the data were collected and the calibration activities were finished, I focused on the analysis of these data. The goal of my analysis is to fully characterize the instrument performances in a condition representative of the mission (i.e., polarimeter integrated in the coronagraph, with the others optics and in vacuum). The instrument performances were analyzed to verify that the science goal of Metis could be achieved. The output of this analysis are: the polarimeter demodulation matrix and the detector flat field map. The former will be used to compute the Stokes vector of the solar corona. The latter is necessary to correct the acquired images by removing artifacts from 2-D images that are caused by variations in the pixel-to-pixel sensitivity of the detector. This work has been performed in collaboration with G.Capobianco and S.Fineschi of INAF-Osservatorio Astrofisico di Torino (OATo) and the Metis scientific team. 2. Algorithms for the Formation-flying metrology of Proba-3. This activity concerns the ESA mission Proba-3, designed to demonstrate technologies for the on orbit flight formation (FF) attitude capability of two different satellites: the Coronagraph Spacecraft (CSC), which will host the Coronagraph ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun) as primary payload, and the Occulter Spacecraft (OSC). This year I worked at the algorithm, based on the use of Shadows Positioning Sensors (SPS), for determining the relative position of the two satellites. The SPS are located on the CSC and measure the intensity of the penumbra illumination level, generated by the OSC, at eight different points within the plane of the entrance of the pupil of the Coronagraph. In particular, I encoded and tested the SPS algorithm for the formation-flying in MATLAB. As a result, I obtained an estimate of the error related to the SPS algorithm in different simulated operational profiles. The code is designed to be used in the loop of the Guidance and Navigation Control system of the spacecraft. This year, using the different input, I defined the pipeline for the on-board SPS data processing. This work has been performed in collaboration with A.Bemporad and S.Fineschi of INAF OATo. Publications: "An improved version of the Shadow Position Sensor readout electronics on board the ESA PROBA-3 Mission", V. Noce, M. Focardi, S. Buckley, A. Bemporad, S. Fineschi, M. Pancrazzi, F. Landini, C. Baccani, G. Capobianco, D. Loreggia, M. Casti, M. Romoli, L. Accatino, C. Thizy, F. Denis, P. Ledent, SPIE 10397, UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XX, 103971B (29 August 2017); doi: 10.1117/12.2273694. "Test plan for the PROBA3/ASPIICS scaled model measurement campaign", Federico Landini, Cristian Baccani, Sébastien Vives, Silvano Fineschi, Marco Romoli, Gerardo Capobianco, Giuseppe Massone, Marta Casti, Alessandro Bemporad, Mauro Focardi, Maurizio Pancrazzi, Davide Loreggia, Vladimiro Noce, Alain Jody Corso, Cédric Thizy, Etienne Renotte, Benoît Marquet; Proc. SPIE 10397, UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XX, 103971C (29 August 2017); doi: 10.1117/12.2273921