Laser frequency combs (LFCs) are optical devices that produce a series of equally spaced spectral lines that can serve as precise and stable references for spectroscopic calibration. ESO has already since several years, laser frequency combs systems in routine operation for the HARPS and the ESPRESSO instruments. We discuss the challenges and solutions for maintaining and operating the LFCs for daily calibrations, and latest achieved performances are presented. Open issues are outlined as well.
CRIRES+ extended the capabilities of CRIRES, the CRyogenic InfraRed Echelle Spectrograph. It transformed this VLT instrument into a cross-dispersed spectrograph to increase the wavelength range that is covered simultaneously by a factor of ten. In addition, a new detector focal plane array of three Hawaii 2RG detectors with a 5.3 μm cut-off wavelength replaced the existing detectors. Amongst many other improvements a new spectropolarimetric unit was added and the calibration system has been enhanced. The instrument was installed at the VLT on Unit Telescope 3 beginning of 2020 and successfully commissioned and verified for science operations during 2021, partly remote from Europe due to the pandemic. The instrument was subsequently offered to the community from October 2021 onwards. This article describes the performance and capabilities of this development and presents on sky results.
FIDEOS (FIbre Dual Echelle Optical Spectrograph) is a fibre-fed bench-mounted high-resolution echelle spec- trograph for the 1-m telescope at ESO in La Silla, Chile. It is based on a 44.41 lines/mm 70° blaze angle
echelle grating in quasi-Littrow mode, providing spectral resolution of R ~ 42 000, covering the spectral range from 400 nm to 680 nm. The detector is a 2k×2k CCD with 15 μm pixels. The spectrograph will be fed by two 50
µm core diameter fibres for the astronomical object and the simultaneous calibration lamp, respectively. Alter- natively, an iodine cell will be mounted on the telescope-spectrograph interface, providing a secondary spectral calibration source. In addition, the instrument will be mounted on a fixed optical-bench without movable parts rather than the CCD shutter and its enclosure will be thermally controlled to ensure opto-mechanical stability. Since the FIDEOS will deliver high resolution and spectral stability, it will be optimized for precision radial velocities.
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