Visible-light channel of the Metis/Solar Orbiter coronagraph: On-ground polarimetric calibration

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985815%3A_____%2F25%3A00639435" target="_blank" >RIV/67985815:_____/25:00639435 - isvavai.cz</a>

Result on the web

<a href="https://hdl.handle.net/11104/0369959" target="_blank" >https://hdl.handle.net/11104/0369959</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1051/0004-6361/202452951" target="_blank" >10.1051/0004-6361/202452951</a>

Result language

angličtina

Original language name

Visible-light channel of the Metis/Solar Orbiter coronagraph: On-ground polarimetric calibration

Original language description

Context. Metis is the solar coronagraph on board the ESA/NASA mission Solar Orbiter (SolO), launched in 2020. It is designed to acquire simultaneous images of the solar corona in visible polarized light (580-640 nm), and in the narrowband H I Lyman-alpha line (i.e., 121.6 nm). The instrument visible-light channel includes a polarimeter composed of two liquid crystal variable retarder (LCVR) cells, a quarter-wave plate, and a linear polarizer, with the LCVR cells acting as the modulating element. By applying a specific voltage to the cells, it is possible to modify the incoming polarized light by changing the direction of the associated vector by a known angle, i.e., the angle of retardance. Aims. The polarimetric characterization of Metis is needed to correctly derive the properties of the plasma in the observed solar corona. This work describes the steps we took to fully characterize the visible channel of the Metis coronagraph, i.e., by deriving the modulation and demodulation matrices for each pixel, the latter being the key element for deriving the Stokes vector of the observed K corona. We completed the characterization by deriving the error associated with the derived values. Methods. The first step is to fully characterize the Metis polarimeter. This is needed to derive the relation between the voltage applied to the liquid crystal cells and the angle of retardance imposed on the incoming polarized light. This step represents the starting point for the calibration of the full instrument. Results. We derived (i) the voltage versus retardance curve associated with the polarimeter and (ii) the demodulation tensor of the Metis coronagraph, which is now used to retrieve the Stokes vector that describes the coronal light polarization state. Conclusions. This calibration is fundamental to disentangle the coronal light from the instrumental effects, such as disuniformity and instrumental polarization.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10308 - Astronomy (including astrophysics,space science)

Project

—

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2025

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Astronomy & Astrophysics

ISSN

0004-6361

e-ISSN

1432-0746

Volume of the periodical

701

Issue of the periodical within the volume

Sept.

Country of publishing house

FR - FRANCE

Number of pages

11

Pages from-to

A197

UT code for WoS article

001574075800008

EID of the result in the Scopus database

2-s2.0-105016453230