The Gregor Infrared Spectrograph (GRIS) is installed at the Gregor telescope at Observatorio del Teide, Spain. The instrument started observations in 2012 and underwent several upgrades in the following years. Currently, it is experiencing the most significant upgrade so far, which includes, among other things, adding two optical channels to perform simultaneous multi-wavelength observations. One of the elements we need to modify to optimise the performance of the instrument on all the new spectral channels is the Polarisation Module Unit (PMU). In this contribution, we want to present our theoretical analysis, laboratory experiments, and first-light results related to the new version of the PMU. This new version and many of the improved capabilities of the instrument will be offered to the community gradually during 2024.
The European Solar Telescope (EST) will be Europe’s most ambitious ground-based infrastructure in solar physics. It will have a primary mirror with a diameter of 4.2m, which will make it the largest in Europe, and of identical aperture as the largest solar telescope available worldwide, namely the Daniel K. Inouye Telescope (DKIST) installed at the Haleakala summit, Hawai'i. EST will have two main characteristics devoted to maximising the scientific return. First, the telescope’s optical path will be polarisation-free using pairs of mirrors that compensate for instrumental polarisation. Second, the telescope will be designed together with a complete instrument suite with imaging and spectrograph instruments. EST will also bring many new technologies, such as a multi-conjugate adaptive optics system and integral field spectro-polarimeters. This contribution presents the conceptual design of the infrared (1 to 1.8 microns) integral field spectropolarimeter. The instrument will have an integral field unit composed of a mirror-based image slicer as input to a Czerny-Turner spectrograph. It will have a polarimeter to record the polarisation state of light on a dual-beam configuration to ensure high-precision spectro-polarimetry.
The GREGOR Infrared Spectrograph (GRIS) can perform spectropolarimetric observations in the infrared. The spectrograph has a Czerny-Turner design and offered traditional long-slit observations since 2014. Later on, in 2018, it was upgraded with an Integral Field Unit (IFU) based on a slicer mirror, which has slicers of 100-μm width. The latter option makes GRIS a unique instrument in solar physics that, after more than 10 years of operation, is still at the forefront of the field, particularly in the infrared. A third upgrade took place in 2021, where optomechanical, control and software improvements have been conducted to introduce new optical channels that operate below 1 μm. These new spectral channels allow simultaneous observations with the previous infrared camera. Between these improvements, a new diffraction grating was installed to enable multi-wavelength configurations with high scientific potential. This new diffraction grating will be interchangeable with the previous one, offering flexibility between spectral resolution, simultaneity, and spectral coverage. Additionally, two more IFUs will be offered to the community. One IFU with a 70-μm width slicer mirror that has already been manufactured and tested at the telescope, and the second with a 35-μm width slicer mirror that is currently at development status. The three IFUs will be interchangeable and offer three different spatial resolution modes and fields of view. This work presents the final optical configuration of the upgraded GRIS and the installation procedure of the most recent upgrades.
The European Solar Telescope (EST), with its primary mirror of 4.2 diameter, will be the largest solar telescope available in Europe. EST will offer Integral Field Spectropolarimetry (IFS) by incorporating the EST spectropolariMeter Based on slicEr-mirrors for the near-infraRed (EMBER). This instrument is a high-resolution spectropolarimeter that allows for the analysis of a 2D field of view by using a slicer mirror-based Integral Field Unit (IFU) as input to the spectrograph. The slicer mirror, which is placed at the focal plane of the telescope, allows the observation of the integral field of view by slicing the entire field. After that, an optical system reorganizes the field of view and provides the spectrograph with an output slit composed of multiple slitlets. The spectrograph has a Czerny-Turner design and will cover the solar spectrum from 1 to 1.8 μm. Additionally, EMBER will offer spectropolarimetry observations with a dual-beam configuration. In this contribution, we present the conceptual optical design of the spectrograph and the IFU as a solution that meets the scientific requirements.
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