In-flight radiometric calibration of the Metis UV H I Ly-αα channel and comparison with UVCS data

Y. De Leo; A. Burtovoi; L. Teriaca; M. Romoli; V. Andretta; M. Uslenghi; S. Giordano; P. Chioetto; R. Susino; F. Landini; M. Pancrazzi; F. Frassati; G. Russano; D. Spadaro; L. Abbo; A. Bemporad; G. Capobianco; G. Capuano; C. Casini; M. Casti; A. J. Corso; V. Da Deppo; M. Fabi; S. Fineschi; F. Frassetto; M. Giarrusso; C. Grimani; S. L. Guglielmino; P. Heinzel; G. Jerse; A. Liberatore; E. Magli; G. Massone; M. Messerotti; J. D. Moses; G. Naletto; G. Nicolini; M. G. Pelizzo; P. Romano; C. Sasso; U. Schühle; T. Straus; A. Slemer; M. Stangalini; D. Telloni; C. A. Volpicelli; L. Zangrilli; P. Zuppella

doi:10.1051/0004-6361/202450759

In-flight radiometric calibration of the Metis UV H I Ly-αα channel and comparison with UVCS data

Y. De Leo
, A. Burtovoi
, L. Teriaca
, M. Romoli
, V. Andretta
, M. Uslenghi
, S. Giordano
, P. Chioetto
, R. Susino
, F. Landini
, M. Pancrazzi
, F. Frassati
, G. Russano
, D. Spadaro
, L. Abbo
, A. Bemporad
, G. Capobianco
, G. Capuano
, C. Casini
, M. Casti

A. J. Corso, V. Da Deppo, M. Fabi, S. Fineschi, F. Frassetto, M. Giarrusso, C. Grimani, S. L. Guglielmino, P. Heinzel, G. Jerse, A. Liberatore, E. Magli, G. Massone, M. Messerotti, J. D. Moses, G. Naletto, G. Nicolini, M. G. Pelizzo, P. Romano, C. Sasso, U. Schühle, T. Straus, A. Slemer, M. Stangalini, D. Telloni, C. A. Volpicelli, L. Zangrilli, P. Zuppella

Max-Planck-Institut für Sonnensystemforschung
INAF Osservatorio Astrofisico di Catania
University of Graz
University of Florence
Istituto di Astrofisica e Planetologia Spaziali (IAPS)
Osservatorio Astrofisico Di Arcetri
INAF Istituto di Astrofisica Spaziale e Fisica Cosmica, Milan
Ev-K2-CNR Committee
Università degli Studi di Catania
CNR-IMM
CISAS
Catholic University of America
University of Urbino Carlo Bo
Istituto Nazionale di Fisica Nucleare, Sezione di Firenze
of Sciences
Wroclaw University
INAF-Trieste
California Institute of Technology
Politecnico di Torino
GSFC Laboratory for Atmopsheres
University of Padova
Science and Research Directorate

Résultats de recherche: Contribution à un journal › Article › Revue par des pairs

Résumé

Context. We present the results of the in-flight radiometric calibration performed for the ultraviolet (UV) H I Ly-α channel of the Metis coronagraph on board Solar Orbiter. Aims. The radiometric calibration is a fundamental procedure required to produce data in physical units. The quantity that allows us to pass from raw data into calibrated data is the radiometric calibration factor, ϵ_UV. Methods. To obtain the ϵ_UV results, we used observations of stellar targets transiting the Metis field of view. We derived ϵ_UV by determining the signal of each calibration star by means of the aperture photometry and evaluating its expected flux in the Metis narrow bandpass (121.6 ± 10 nm). The analyzed data cover a time range from the beginning of the Cruise Phase in June 2020, up until August 2021. Results. We find that the UV channel requires a significant additional correction of the response across the field of view, compared to that provided by the vignetting function measured on the ground and refined in flight, specifically tailored to the UV channel. This correction is provided by the ratio of images of the back-illumination of the closed door. Here, we use the stellar measurements to refine and improve such a correction map. After correcting for the spatial disuniformity, a radiometric calibration factor ϵ_UV = 0.20 ± 0.03 DN/photon was found. No significant changes in the UV channel throughput were observed during the period from June 2020 to August 2021. In addition, the analysis of a smaller number of stars observed in 2022 and 2023 enabled us to extend the validity of the radiometric calibration to that period, after considering a suitable scaling factor due to the change of operating voltages occurred in April 2022. From this second analysis, the value of the radiometric calibration factor is ϵ_UV = 0.11 ± 0.03 DN/photon. In order to support the radiometric calibration results, we performed a comparison between average radial profiles of the H I Ly-α intensity obtained from Metis UV images acquired in 2020-2021 and those measured with the UltraViolet Coronagraph Spectrometer (UVCS) on board the Solar and Heliospheric Observatory (SOHO) during the period of the activity minimum of solar cycle 22 in 1996. We found that intensity profiles of these instruments are consistent with each other.

langue originale	Anglais
Numéro d'article	A73
journal	Astronomy and Astrophysics
Volume	697
Les DOIs	https://doi.org/10.1051/0004-6361/202450759
état	Publié - 1 mai 2025
Modification externe	Oui

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10.1051/0004-6361/202450759

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De Leo, Y., Burtovoi, A., Teriaca, L., Romoli, M., Andretta, V., Uslenghi, M., Giordano, S., Chioetto, P., Susino, R., Landini, F., Pancrazzi, M., Frassati, F., Russano, G., Spadaro, D., Abbo, L., Bemporad, A., Capobianco, G., Capuano, G., Casini, C., ... Zuppella, P. (2025). In-flight radiometric calibration of the Metis UV H I Ly-αα channel and comparison with UVCS data. Astronomy and Astrophysics, 697, Article A73. https://doi.org/10.1051/0004-6361/202450759

@article{f1df9737e8ed4aeaaf4e1422aede884c,

title = "In-flight radiometric calibration of the Metis UV H I Ly-αα channel and comparison with UVCS data",

abstract = "Context. We present the results of the in-flight radiometric calibration performed for the ultraviolet (UV) H I Ly-α channel of the Metis coronagraph on board Solar Orbiter. Aims. The radiometric calibration is a fundamental procedure required to produce data in physical units. The quantity that allows us to pass from raw data into calibrated data is the radiometric calibration factor, ϵUV. Methods. To obtain the ϵUV results, we used observations of stellar targets transiting the Metis field of view. We derived ϵUV by determining the signal of each calibration star by means of the aperture photometry and evaluating its expected flux in the Metis narrow bandpass (121.6 ± 10 nm). The analyzed data cover a time range from the beginning of the Cruise Phase in June 2020, up until August 2021. Results. We find that the UV channel requires a significant additional correction of the response across the field of view, compared to that provided by the vignetting function measured on the ground and refined in flight, specifically tailored to the UV channel. This correction is provided by the ratio of images of the back-illumination of the closed door. Here, we use the stellar measurements to refine and improve such a correction map. After correcting for the spatial disuniformity, a radiometric calibration factor ϵUV = 0.20 ± 0.03 DN/photon was found. No significant changes in the UV channel throughput were observed during the period from June 2020 to August 2021. In addition, the analysis of a smaller number of stars observed in 2022 and 2023 enabled us to extend the validity of the radiometric calibration to that period, after considering a suitable scaling factor due to the change of operating voltages occurred in April 2022. From this second analysis, the value of the radiometric calibration factor is ϵUV = 0.11 ± 0.03 DN/photon. In order to support the radiometric calibration results, we performed a comparison between average radial profiles of the H I Ly-α intensity obtained from Metis UV images acquired in 2020-2021 and those measured with the UltraViolet Coronagraph Spectrometer (UVCS) on board the Solar and Heliospheric Observatory (SOHO) during the period of the activity minimum of solar cycle 22 in 1996. We found that intensity profiles of these instruments are consistent with each other.",

keywords = "Sun: corona",

author = "\{De Leo\}, Y. and A. Burtovoi and L. Teriaca and M. Romoli and V. Andretta and M. Uslenghi and S. Giordano and P. Chioetto and R. Susino and F. Landini and M. Pancrazzi and F. Frassati and G. Russano and D. Spadaro and L. Abbo and A. Bemporad and G. Capobianco and G. Capuano and C. Casini and M. Casti and Corso, \{A. J.\} and \{Da Deppo\}, V. and M. Fabi and S. Fineschi and F. Frassetto and M. Giarrusso and C. Grimani and Guglielmino, \{S. L.\} and P. Heinzel and G. Jerse and A. Liberatore and E. Magli and G. Massone and M. Messerotti and Moses, \{J. D.\} and G. Naletto and G. Nicolini and Pelizzo, \{M. G.\} and P. Romano and C. Sasso and U. Sch{\"u}hle and T. Straus and A. Slemer and M. Stangalini and D. Telloni and Volpicelli, \{C. A.\} and L. Zangrilli and P. Zuppella",

note = "Publisher Copyright: {\textcopyright} The Authors 2025.",

year = "2025",

month = may,

day = "1",

doi = "10.1051/0004-6361/202450759",

language = "English",

volume = "697",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

}

De Leo, Y, Burtovoi, A, Teriaca, L, Romoli, M, Andretta, V, Uslenghi, M, Giordano, S, Chioetto, P, Susino, R, Landini, F, Pancrazzi, M, Frassati, F, Russano, G, Spadaro, D, Abbo, L, Bemporad, A, Capobianco, G, Capuano, G, Casini, C, Casti, M, Corso, AJ, Da Deppo, V, Fabi, M, Fineschi, S, Frassetto, F, Giarrusso, M, Grimani, C, Guglielmino, SL, Heinzel, P, Jerse, G, Liberatore, A, Magli, E, Massone, G, Messerotti, M, Moses, JD, Naletto, G, Nicolini, G, Pelizzo, MG, Romano, P, Sasso, C, Schühle, U, Straus, T, Slemer, A, Stangalini, M, Telloni, D, Volpicelli, CA, Zangrilli, L & Zuppella, P 2025, 'In-flight radiometric calibration of the Metis UV H I Ly-αα channel and comparison with UVCS data', Astronomy and Astrophysics, VOL. 697, A73. https://doi.org/10.1051/0004-6361/202450759

TY - JOUR

T1 - In-flight radiometric calibration of the Metis UV H I Ly-αα channel and comparison with UVCS data

AU - De Leo, Y.

AU - Burtovoi, A.

AU - Teriaca, L.

AU - Romoli, M.

AU - Andretta, V.

AU - Uslenghi, M.

AU - Giordano, S.

AU - Chioetto, P.

AU - Susino, R.

AU - Landini, F.

AU - Pancrazzi, M.

AU - Frassati, F.

AU - Russano, G.

AU - Spadaro, D.

AU - Abbo, L.

AU - Bemporad, A.

AU - Capobianco, G.

AU - Capuano, G.

AU - Casini, C.

AU - Casti, M.

AU - Corso, A. J.

AU - Da Deppo, V.

AU - Fabi, M.

AU - Fineschi, S.

AU - Frassetto, F.

AU - Giarrusso, M.

AU - Grimani, C.

AU - Guglielmino, S. L.

AU - Heinzel, P.

AU - Jerse, G.

AU - Liberatore, A.

AU - Magli, E.

AU - Massone, G.

AU - Messerotti, M.

AU - Moses, J. D.

AU - Naletto, G.

AU - Nicolini, G.

AU - Pelizzo, M. G.

AU - Romano, P.

AU - Sasso, C.

AU - Schühle, U.

AU - Straus, T.

AU - Slemer, A.

AU - Stangalini, M.

AU - Telloni, D.

AU - Volpicelli, C. A.

AU - Zangrilli, L.

AU - Zuppella, P.

PY - 2025/5/1

Y1 - 2025/5/1

N2 - Context. We present the results of the in-flight radiometric calibration performed for the ultraviolet (UV) H I Ly-α channel of the Metis coronagraph on board Solar Orbiter. Aims. The radiometric calibration is a fundamental procedure required to produce data in physical units. The quantity that allows us to pass from raw data into calibrated data is the radiometric calibration factor, ϵUV. Methods. To obtain the ϵUV results, we used observations of stellar targets transiting the Metis field of view. We derived ϵUV by determining the signal of each calibration star by means of the aperture photometry and evaluating its expected flux in the Metis narrow bandpass (121.6 ± 10 nm). The analyzed data cover a time range from the beginning of the Cruise Phase in June 2020, up until August 2021. Results. We find that the UV channel requires a significant additional correction of the response across the field of view, compared to that provided by the vignetting function measured on the ground and refined in flight, specifically tailored to the UV channel. This correction is provided by the ratio of images of the back-illumination of the closed door. Here, we use the stellar measurements to refine and improve such a correction map. After correcting for the spatial disuniformity, a radiometric calibration factor ϵUV = 0.20 ± 0.03 DN/photon was found. No significant changes in the UV channel throughput were observed during the period from June 2020 to August 2021. In addition, the analysis of a smaller number of stars observed in 2022 and 2023 enabled us to extend the validity of the radiometric calibration to that period, after considering a suitable scaling factor due to the change of operating voltages occurred in April 2022. From this second analysis, the value of the radiometric calibration factor is ϵUV = 0.11 ± 0.03 DN/photon. In order to support the radiometric calibration results, we performed a comparison between average radial profiles of the H I Ly-α intensity obtained from Metis UV images acquired in 2020-2021 and those measured with the UltraViolet Coronagraph Spectrometer (UVCS) on board the Solar and Heliospheric Observatory (SOHO) during the period of the activity minimum of solar cycle 22 in 1996. We found that intensity profiles of these instruments are consistent with each other.

AB - Context. We present the results of the in-flight radiometric calibration performed for the ultraviolet (UV) H I Ly-α channel of the Metis coronagraph on board Solar Orbiter. Aims. The radiometric calibration is a fundamental procedure required to produce data in physical units. The quantity that allows us to pass from raw data into calibrated data is the radiometric calibration factor, ϵUV. Methods. To obtain the ϵUV results, we used observations of stellar targets transiting the Metis field of view. We derived ϵUV by determining the signal of each calibration star by means of the aperture photometry and evaluating its expected flux in the Metis narrow bandpass (121.6 ± 10 nm). The analyzed data cover a time range from the beginning of the Cruise Phase in June 2020, up until August 2021. Results. We find that the UV channel requires a significant additional correction of the response across the field of view, compared to that provided by the vignetting function measured on the ground and refined in flight, specifically tailored to the UV channel. This correction is provided by the ratio of images of the back-illumination of the closed door. Here, we use the stellar measurements to refine and improve such a correction map. After correcting for the spatial disuniformity, a radiometric calibration factor ϵUV = 0.20 ± 0.03 DN/photon was found. No significant changes in the UV channel throughput were observed during the period from June 2020 to August 2021. In addition, the analysis of a smaller number of stars observed in 2022 and 2023 enabled us to extend the validity of the radiometric calibration to that period, after considering a suitable scaling factor due to the change of operating voltages occurred in April 2022. From this second analysis, the value of the radiometric calibration factor is ϵUV = 0.11 ± 0.03 DN/photon. In order to support the radiometric calibration results, we performed a comparison between average radial profiles of the H I Ly-α intensity obtained from Metis UV images acquired in 2020-2021 and those measured with the UltraViolet Coronagraph Spectrometer (UVCS) on board the Solar and Heliospheric Observatory (SOHO) during the period of the activity minimum of solar cycle 22 in 1996. We found that intensity profiles of these instruments are consistent with each other.

KW - Sun: corona

UR - https://www.scopus.com/pages/publications/105005299801

U2 - 10.1051/0004-6361/202450759

DO - 10.1051/0004-6361/202450759

M3 - Article

AN - SCOPUS:105005299801

SN - 0004-6361

VL - 697

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

M1 - A73

ER -

In-flight radiometric calibration of the Metis UV H I Ly-αα channel and comparison with UVCS data

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