A new facility instrument open to the scientific community is MISTRAL. The MIllimeter Sardinia radio Telescope Receiver based on Array of Lumped elements KIDs (MISTRAL) is a millimetric multi–pixel camera, mounted at the Gregorian focus of the Sardinia Radio Telescope (SRT), working in the W-band that will be able to study many scientific cases, from the ‘missing baryons’ problem to extragalactic astrophysics, morphology of galaxy cluster and the search of the Cosmic Web through high angular resolution measurements of the Sunyaev-Zel’dovich effect. We present the current state of the map-making and data filtering software that we plan to use for future observations. This software aims to analyze the simulated observations of a target, filter the data from instrumental noise and produce a map, employing a customized common mode removal.
The Millimeter Sardinia radio Telescope Receiver based on Array of Lumped elements KIDs (MISTRAL) is a new high resolution, wide field-of-view camera that was successfully installed in May 2023 at the Sardinia Radio Telescope (SRT). SRT is a 64m fully steerable gregorian radio telescope, and it underwent an upgrade funded by a National Operational Program (PON) with the aim to expand the fleet of receivers of the radio telescope in order to cover frequency up to the W–band. The W-band sky has been extensively studied by Cosmic Microwave Background experiments, both ground-based (ACT, SPT) and satellite-based (WMAP, Planck). However, their resolution is limited to ≈1′ from ground telescopes and ≈10′ from satellite at best. With this new instrument, we aim to map the microwave sky at a resolution of ≈12′′, a capability only shared by few instruments in the world, unlocking the exploration of a plethora of science cases from the recently upgraded SRT. The heart of MISTRAL is a ≈90mm silicon focal plane populated with 415 cryogenic Lumped Elements Kinetic Inductance Detectors (LEKIDs). These detectors are copuled with the telescope using a cold (4K) re-imaging optical system, producing a diffraction limited field-of-view of 4 ′. The system is enclosed in a custom, four stage cryostat, built with strict requirements on its size, in order to fit on the rotating turret that allows to switch the receivers to be quickly moved in and out of the gregorian focus position. The sub-K stage cools the detectors down to 200-240 mK. MISTRAL is now installed on the gregorian focus of SRT and is undergoing the technical commissioning, and will soon enter the scientific commissioning phase. In this contribution we will survey the subsystems of MISTRAL and their performance at the focus of the radio telescope, and report the current status of the technical commissioning.
The LiteBIRD mission is dedicated to the search for primordial B modes in the Cosmic Microwave Background (CMB) polarization. To achieve unprecedented sensitivity and accuracy in this measurement, the control of instrument systematics is paramount. In this context, we describe the development of microwave absorbers needed to mitigate the straylight within the telescope tubes of the LiteBIRD Mid- and High-Frequency Telescopes (MHFT). A baseline solution has been designed and validated using HFSS simulations, consistently demonstrating sub-percent level specular reflectance across the entire 90-448 GHz band of the MHFT under a broad variety of incidence conditions, representative of the actual optical environment predicted for the two telescopes. Leveraging consolidated technologies, a prototype has been manufactured and characterized in laboratory, demonstrating a promising reflectance mitigation despite the deviation from the nominal geometry. Ongoing parallel efforts involve a comprehensive investigation (both through simulations and laboratory measurements) of the requirements to be finalized in order to define the practical implementation of the baseline design. This activity will ultimately ensure the alignment with allocated thermo-mechanical requirements along with the compliance with the desired electromagnetic performance. The presented studies not only solidify the feasibility of the straylight mitigation approach, but also inform the finalization of the optical tube design, in view of the conclusion of the CNES Phase A study of LiteBIRD.
The MISTRAL instrument is a cryogenic, W-band camera consisting of 415 lumped element kinetic inductance detectors. In a significant milestone achieved in May 2023, MISTRAL was successfully installed at the Gregorian focus of the Sardinia Radio Telescope, a 64m aperture telescope in Italy. MISTRAL has a focal plane of ~ 94mm in diameter, resulting in an instantaneous field of view ~ 4 arcmin. To preserve the high angular resolution of the telescope, which is ~ 12 arcsec, the focal plane sampling has been tuned to 4.2 mm, corresponding to a pixel separation of ~ 10.6 arcsec. The remarkable combination of high angular resolution and wide instantaneous field of view makes MISTRAL an exceptionally versatile tool for continuum surveys of wide areas of the sky. Its unique capabilities significantly enhance the observational capacity of the Sardinia Radio Telescope. The lumped element kinetic inductance detectors of MISTRAL are obtained from a titanium-aluminum bilayer 10 + 30nm thick on a single 100 mm–diameter Silicon wafer with thickness 235 μm. They exhibit a critical temperature of 945mK and are optimized to operate within the temperature range of 200 to 240 mK. The feedline is made of an aluminum 21nm thick and has a critical temperature of 1.35 K. We discuss the design, electrical, and optical characterization of the detector array, placing specific emphasis on the yield, the pixel identification on the array, the optical performance, and the calibration procedures.
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