We present first on-sky performance results of KalAO, the natural guide star adaptive optics imager on the 1.2m Swiss telescope in La Silla, Chile. It is designed to reach at least 30% Strehl in order to detect stellar companions as close as the 150mas in visible-light, at diffraction limit. KalAO was built to search for binarity in planet hosting stars by following-up planet candidates primarily from the TESS satellite survey. The optical design is optimised for the 450 to 900nm wavelength range and is fitted with SDSS griz filters. Wavefront control works down to I-magnitude 10 stars in order to probe the same parameter space as radial velocity instruments such as HARPS and NIRPS. The system first closed the loop on sky in November 2023 and reached diffraction limit imaging in February 2024. It can carry out AO corrected observation of up to 500 targets in one night, with a Strehl ratio of ≈30%.
NIRPS is a fiber-fed AO nIR spectrograph working simultaneously with HARPS at the La Silla-ESO 3.6m telescope. The cryogenic spectrograph operating at 75K employs a cross-dispersed echelle grating (R4), covering a wavelength range of 0.98-1.80 microns in a single image using a Teledyne Hawaii-4RG infrared detector. In early 2022, the NIRPS spectrograph was transported to Chile by plane with all the optical elements mechanically attached to the optical bench inside the vaccum vessel. To ensure the safety of the spectrograph, dedicated work was performed on the shipping crate design, which could survive up to 7g shocks. In La Silla, the vacuum vessel was re-integrated on its support structure and the spectrograph alignment was verified with the H4RG and the injection module. Given the optical design, the alignment phase was performed using a metrology arm and a few optical tests, which minimize the time required for this critical phase. From the validation/technical phase results, two major modifications were required. Firstly, the original grating element was replaced by a new etched crystalline silicon component made by the Fraunhofer Institute for Applied Optics and Precision Engineering. A novel technique was developed to verify the alignment at a warm temperature with the H4RG detector. Secondly, a thermal enclosure was added around the vacuum vessel to optimize thermal stability. Since then, the long-term thermal stability has been better than 0.2mK over 20 days. In this paper, we will review the final spectrograph performances, prior to shipping, and describe the novel techniques developed to minimize shipping costs, AITV phase duration, and grating replacement at the observatory. Additionally, we will discuss the thermal enclosure design to achieve the sub-mK thermal stability.
NIRPS is a near-infrared (YJH bands), fiber-fed, high-resolution precise radial velocity (PRV) spectrograph installed at the ESO 3.6-m telescope in La Silla, Chile. Using a dichroic, NIRPS will be operated simultaneously with the optical HARPS PRV spectrograph and will be used to conduct ambitious planet-search and characterization surveys. NIRPS aims at detecting and characterizing Earth-like planets in the habitable zone of low-mass dwarfs and obtain high-accuracy transit spectroscopy of exoplanets. The spectrograph is compact for better thermal stability. Using a custom R4 grating in combination with a state-of-the-art Hawaii4RG detector, the instrument provides a high resolution and high stability over the range of 950-1800 nm. This paper focuses on the lens and optomechanical design, assembly, and test of NIRPS’s spectrograph. Some performance tests conducted at Université Laval (Canada) during the integration and at La Silla during commissioning are presented
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