Cryogenic detector preamplifer developments at the ANU

We present a summary of the cryogenic detector preamplifier development programme under way at the ANU. Cryogenic preamplifiers have been demonstrated for both near-infrared detectors (Teledyne H1RG and Leonardo SAPHIRA eAPD as part of development for the GMTIFS instrument) and optical CCDs (e2v CCD231-84 for use with the AAT/Veloce spectrograph). This approach to detector signal conditioning allows low-noise instrument amplifiers to be placed very close to an infra-red detector or optical CCD, isolating the readout path from external interference noise sources. Laboratory results demonstrate effective isolation of the readout path from external interference noise sources. Recent progress has focussed on the first on-sky deployment of four cryogenic preamp channels for the Veloce Rosso precision radial velocity spectrograph. We also outline future evolution of the current design, allowing higher speeds and further enhanced performance for the demanding applications required for the on instrument wavefront sensor on the Giant Magellan Integral Field Spectrograph (GMTIFS).This research was supported under Australian Research Council's Linkage Project funding scheme (LP150100620) in partnership with the Australian National University and Giant Magellan Telescope Organisation

Design of the near infrared camera DIRAC for East Anatolia Observatory

The 4m DAG telescope is under construction at East Anatolia Observatory in Turkey. DIRAC, the “DAG InfraRed Adaptive optics Camera”, is one of the facility instruments. This paper describes the design of the camera to meet the performance specifications. Adaptive and auxiliary optics relay the telescope F/14 input 1:1 into DIRAC. The camera has an all refractive design for the wavelength range 0.9 - 2.4 micron. Lenses reimage the telescope focal plane 33 x 33 as (9 x 9 mm) on a 1k x 1k focal plane array. With magnification of 2x, the plate scale on the detector is 33 mas/pixel. There are 4 standard filters (Y, J, H, K) and 4 narrowband continuum filters. A 12 position filter wheel allows installation of 2 extra customer filters for specific needs; the filter wheel also deploys a pupil viewer lens. Optical tolerancing is carried out to deliver the required image quality at polychromatic Strehl ratio of 90% with focus compensator. This reveals some challenges in the precision assembly of optics for cryogenic environments. We require cells capable of maintaining precision alignment and keeping lenses stress free. The goal is achieved by a combination of flexures with special bonding epoxy matching closely the CTE of the lens cells and crystalline materials. The camera design is very compact with object to image distance <220 mm and lens diameters <25 mm. A standalone cryostat is LN2 cooled for vibration free operation with the bench mounted adaptive optics module (TROIA) and coronagraph (PLACID) at the Nasmyth focus of the DAG telescope

MAVIS on the VLT: A Powerful, Synergistic ELT Complement in the Visible

International audienceOn 1 June 2021 ESO and a consortium of Australian, Italian and French institutions signed an agreement for the design and construction of the MCAO Assisted Visible Imager and Spectrograph (MAVIS). This Very Large Telescope (VLT) instrument will push the frontier of new astronomical instrument technologies to provide, for the first time, wide-field, diffraction-limited angular resolution at visible wavelengths. In combination with the VLT Adaptive Optics Facility, it will use multi- conjugate adaptive optics (MCAO) to feed a 4k × 4k imager covering 30 × 30 arcseconds, as well as an Integral Field Spectrograph (IFS). Angular resolution down to 18 milliarcseconds will be achieved at a wavelength of 550 nm (V band). The IFS will provide four spectral modes, with spectral resolutions from 4000 to over 15000 between 370 and 950 nm. This will enable a wide variety of science cases, spanning themes that include the emergence of the Hubble sequence, resolving the contents of nearby galaxies, star clusters over cosmic time and the birth, life, and death of stars and their planets. Delivering visible images and integral- field spectroscopy at an angular resolution two to three times better than that of the Hubble Space Telescope will make MAVIS a powerful complement at visible wavelengths to future facilities like the James Webb Space Telescope and the 30–40-metre-class ground-based telescopes currently under construction, which are all optimised for science at infrared wavelengths