Polarization modulators based on liquid crystal variable retarders for the Solar Orbiter mission

Alvarez-Herrero, A.; Parejo, Pilar García; Laguna, H.; Villanueva, J.; Barandiarán, J.; Bastide, Laurent; Reina, M.; Sánchez, Antonio; Gonzalo, Alejandro; Navarro, Ramón; Vera, I.; Royo, Miquel

doi:10.1117/12.2188591

Cited by 8 publications

(5 citation statements)

References 4 publications

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“…Using a LCVR avoids the complication of using a mechanical system for precision rotation of the wave plate, such as in GONG, hence reducing the complexity and cost in the design. LCVRs for space application have been demonstrated recently by the SoLO mission (Alvarez-Herrero et al 2015).…”

Section: Discussionmentioning

confidence: 99%

A Compact Full-disk Solar Magnetograph Based on Miniaturization of the GONG Instrument*

Gosain¹,

Harvey²,

Pillet³

et al. 2023

PASP

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The design of compact instruments is crucial for the scientific exploration by smaller spacecraft such as CubeSats and deep space missions, as these missions require minimal instrument mass. In this proof-of-concept study, we demonstrate the miniaturization of the Global Oscillation Network Group (GONG) instrument. GONG instruments routinely produce full-disk maps of the Sun’s photosphere using the Ni i 676 nm absorption line, measuring Doppler shifts and magnetic fields. To miniaturize the GONG optical design, we propose replacing the bulky Lyot filter with a narrow-band interference filter. We validate this concept through numerical modeling and proof-of-concept observations. Finally, we propose a simple optical design for building a compact version of GONG.

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Section: Discussionmentioning

confidence: 99%

A Compact Full-disk Solar Magnetograph Based on Miniaturization of the GONG Instrument*

Gosain¹,

Harvey²,

Pillet³

et al. 2023

PASP

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“…The HRT uses its own Polarisation Modulation Package (PMP), consisting of Liquid Crystal Variable Retarders (LCVR) and a polariser to modulate the light in order to obtain the polarisation characteristics of the incoming light. 7 Once modulated, the light is split and a portion enters the Correlation Tracker Camera (CTC). The CTC is part of the Image Stabilisation System (ISS) which works to track a specific feature on the solar surface, calculating from the CTC images the steering signal for the M2 (tip-tilt) mirror, to accurately track the desired feature.…”

Section: The Instrumentmentioning

confidence: 99%

The on-ground data reduction and calibration pipeline for SO/PHI-HRT

Sinjan¹,

Calchetti

Hirzberger

et al. 2022

Software and Cyberinfrastructure for Astronomy VII

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The ESA/NASA Solar Orbiter space mission has been successfully launched in February 2020. Onboard is the Polarimetric and Helioseismic Imager (SO/PHI), which has two telescopes, a High Resolution Telescope (HRT) and the Full Disc Telescope (FDT). The instrument is designed to infer the photospheric magnetic field and line-of-sight velocity through differential imaging of the polarised light emitted by the Sun. It calculates the full Stokes vector at 6 wavelength positions at the Fe I 617.3 nm absorption line. Due to telemetry constraints, the instrument nominally processes these Stokes profiles onboard, however when telemetry is available, the raw images are downlinked and reduced on ground. Here the architecture of the on-ground pipeline for HRT is presented, which also offers additional corrections not currently available on board the instrument. The pipeline can reduce raw images to the full Stokes vector with a polarimetric sensitivity of 10 −3 • I c or better.

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“…The PMP in fact is the key and most innovative optical element of the polarimeter. Its assembly includes two nematic LCVRs, that are active optical elements that can change the orientation of the LC molecules by application of a suitable low voltage (< 10 V) [2]; thus it is possible to vary in a controlled way the optical retardance of the PMP without the need of any mechanism, which is a clear advantage for space applications. This property is used for the polarimetric analysis, thanks to the adopted de Sénarmont configuration [9] for the polarimeter.…”

Section: Visible Light Channel Optical Pathmentioning

confidence: 99%

Optical design of the multi-wavelength imaging coronagraph Metis for the solar orbiter mission

et al. 2020

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This paper describes the innovative optical design of the Metis coronagraph for the Solar Orbiter ESA-NASA mission. Metis is a multi-wavelength, externally occulted telescope for the imaging of the solar corona in both the visible and ultraviolet wavelength ranges. Metis adopts a novel occultation scheme for the solar disk, that we named “inverse external occulter”, for reducing the extremely high thermal load on the instrument at the spacecraft perihelion. The core of the Metis optical design is an aplanatic Gregorian telescope common to both the visible and ultraviolet channels. A suitable dichroic beam-splitter, optimized for transmitting a narrow-band in the ultraviolet (121.6 nm, HI Lyman-α) and reflecting a broadband in the visible (580–640 nm) spectral range, is used to separate the two optical paths. Along the visible light optical path, a liquid crystal electro-optical modulator, used for the first time in space, allows making polarimetric measurements.

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Polarization modulators based on liquid crystal variable retarders for the Solar Orbiter mission

Cited by 8 publications

References 4 publications

A Compact Full-disk Solar Magnetograph Based on Miniaturization of the GONG Instrument*

A Compact Full-disk Solar Magnetograph Based on Miniaturization of the GONG Instrument*

The on-ground data reduction and calibration pipeline for SO/PHI-HRT

Optical design of the multi-wavelength imaging coronagraph Metis for the solar orbiter mission

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