Design of the VLT-CUBES image slicers:

Abstract

CUBES is a high efficiency spectrograph designed for a Cassegrain focus of the Very Large Telescope and is expected to be in operation in 2028. It is designed to observe point or compact sources in a spectral range from 300 to 405nm. CUBES will provide two spectral resolving powers: R$$\ge$$ ≥ 20,000 for high resolution (HR) and R$$\ge$$ ≥ 5,000 for low resolution (LR). This is achieved by using an image slicer for each resolution mode. The image slicers re-format a rectangular on-sky field of view of either 1.5arcsec by 10arcsec (HR) or 6arcsec by 10arcsec (LR) into six side-by-side slitlets which form the spectrograph slit. The slit dimensions are 0.19mm $$\times$$ × 88mm for HR and 0.77mm $$\times$$ × 88mm for LR. The on-sky and physical widths of the slicer mirrors are 0.25arcsec/0.5mm (HR) and 1arcsec/2mm (LR). The image slicers reduce the spectrograph entrance slit etendue and hence the size of the spectrograph optics without associated slit losses. Each of the proposed image slicers consists of two arrays of six spherical mirrors (slicer mirror and camera mirror arrays) which provide a straight entrance slit to the spectrograph with almost diffraction-limited optical quality. This paper presents the description of the image slicers at the end of the Phase A conceptual design, including their optical design and expected performance.

Spectral Imager of the Solar Atmosphere: The First Extreme-Ultraviolet Solar Integral Field Spectrograph Using Slicers

“…Image slicers have been used for ground-based telescopes in recent decades, operating at different spectral ranges from the infrared to UV/visible, for a wide variety of science cases. Some examples are shown in Figure 3 and include the following: VLT CUBES [90], BlueMUSE [91] and MUSE [92]; GTC FRIDA [93]; GNIRS at Gemini North Telescope or ELT HARMONI [94] and METIS [95] for night-time observation. For solar physics, image slicers were first proposed for the integral field spectrograph [96,97] of the European Solar Telescope, which provides optical observations.…”

SISA: The First Extreme-Ultraviolet Solar Integral Field Spectrograph Using Slicers

“…Image slicers have been used for ground-based telescopes in the last few decades, operating at different spectral ranges from the infrared to UV/visible, for a wide variety of science cases. Some examples are shown in Figure 3 and include: VLT CUBES [88], BlueMUSE [89] and MUSE [90]; GTC FRIDA [91]; GNIRS [92] at Gemini North Telescope or ELT HARMONI [93] and METIS [94] for night-time observation. For solar physics, image slicers were first proposed for the integral field spectrograph [95,96] of the European Solar Telescope, which would observe in the optical.…”

Cometary science with CUBES

“…The CUBES project completed its Phase A conceptual design in mid 2021, and will move into the construction phase in 2022; technical details of the design are outlined elsewhere in this volume [1]. A key aspect of the design for cometary observations is the provision of two resolving powers by using two (exchangeable) image slicers, each with six slices [2]. These provide a high-resolution (HR) mode with R≥ 22 000, with an on-sky field of view of 1.5 �� × 10 �� (and a slice-width of 0.25 ′′ ), and a low-resolution (LR) mode with R≥ 5 000, with a larger field on the sky of 6 �� × 10 �� (and 1 ′′ slices).…”