Development of a 2D precision cryogenic chopper for METIS

Paalvast, S.L.; Janssen, H.; Teuwen, Maurice; Huisman, R.; Brandl, Bernhard R.; Molster, Frank; Venema, Lars

doi:10.1117/12.925338

Cited by 2 publications

(4 citation statements)

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“…It is worth noting that a cryogenic chopper is part of the METIS instrument design for the E-ELT. Details of the development and characterization of such a cryogenic device was presented at this conference 10 .…”

Section: External Choppermentioning

confidence: 99%

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VISIR upgrade overview and status

Kerber¹,

Käufl

Baksai

et al. 2014

SPIE Proceedings

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We present an overview of the VISIR upgrade project. VISIR is the mid-infrared imager and spectrograph at ESO's VLT. The project team is comprised of ESO staff and members of the original VISIR consortium: CEA Saclay and ASTRON. The project plan is based on input from the ESO user community with the goal of enhancing the scientific performance and efficiency of VISIR by a combination of measures: installation of improved hardware, optimization of instrument operations and software support. The cornerstone of the upgrade is the 1k by 1k Si:As AQUARIUS detector array (Raytheon) which has been carefully characterized in ESO's IR detector test facility (modified TIMMI 2 instrument). A prism spectroscopic mode will cover the N-band in a single observation. New scientific capabilities for high resolution and high-contrast imaging will be offered by sub-aperture mask (SAM) and phase-mask coronagraphic (4QPM/AGPM) modes. In order to make optimal use of favourable atmospheric conditions a water vapour monitor has been deployed on Paranal, allowing for real-time decisions and the introduction of a user-defined constraint on water vapour. During the commissioning in 2012 it was found that the on-sky sensitivity of the AQUARIUS detector was significantly below expectations and that VISIR was not ready to go back to science operations. Extensive testing of the detector arrays in the laboratory and on-sky enabled us to diagnose the cause for the shortcoming of the detector as excess low frequency noise (ELFN). It is inherent to the design chosen for this detector and can't be remedied by changing the detector set-up. Since this is a form of correlated noise its impact can be limited by modulating the scene recorded by the detector. We have studied several mitigation options and found that faster chopping using the secondary mirror (M2) of the VLT offers the most promising way forward. Faster M2 chopping has been tested and is scheduled for implementation before the end of 2014 after which we plan to re-commission VISIR. In addition an upgrade of the IT infrastructure related to VISIR is planned in order to support burst-mode operations. The upgraded VISIR will be a powerful instrument providing close to background limited performance for diffraction-limited observations at an 8-m telescope. It will offer synergy with facilities such as ALMA, JWST, VLTI and SOFIA, while a wealth of targets is available from survey work (e.g. VISTA, WISE). In addition it will bring confirmation of the technical readiness and scientific value of several aspects of potential mid-IR instrumentation at Extremely Large Telescopes.

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Section: External Choppermentioning

confidence: 99%

“…We had to conclude that VISIR was not ready for returning to science operations and a dedicated plan was set up to identify the root cause of the lack of sensitivity. Frequency (Hz) 10.00 100.00…”

Section: Commissioning In 2012mentioning

confidence: 99%

VISIR upgrade overview and status

Kerber¹,

Käufl

Baksai

et al. 2014

SPIE Proceedings

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“…The 1∕f noise can be effectively removed by subtracting pairs of observations where the source has been modulated via tip/tilt offsets faster than the characteristic frequency corresponding to the up-turn of the 1∕f noise component. This strategy will be implemented in the ELT/METIS instrument (Brandl et al 2022;Paalvast et al 2014). 4.…”

Section: Mitigation Strategiesmentioning

confidence: 99%

“…The

1/f

noise can be effectively removed by subtracting pairs of observations where the source has been modulated via tip/tilt offsets faster than the characteristic frequency corresponding to the up‐turn of the

1/f

noise component. This strategy will be implemented in the ELT/METIS instrument (Brandl et al 2022; Paalvast et al 2014). For low‐background observations, a CDS or SUR mode may provide an effective way to subtraction out the

1/f

noise if signal accumulation is low.…”

Section: Excess Noise Analysismentioning

confidence: 99%

Evaluating the GeoSnap 13‐μ$$ \mu $$m cutoff HgCdTe detector for mid‐IR ground‐based astronomy

et al. 2023

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New mid‐infrared HgCdTe (MCT) detector arrays developed in collaboration with Teledyne Imaging Sensors (TIS) have paved the way for improved 10‐m sensors for space‐ and ground‐based observatories. Building on the successful development of longwave HAWAII‐2RGs for space missions such as NEO Surveyor, we characterize the first 13‐m GeoSnap detector manufactured to overcome the challenges of high‐background rates inherent in ground‐based mid‐IR astronomy. This test device merges the longwave HgCdTe photosensitive material with Teledyne's GeoSnap‐18 (18‐m pixel) focal plane module, which is equipped with a capacitive transimpedance amplifier (CTIA) readout circuit paired with an onboard 14‐bit analog‐to‐digital converter (ADC). The final assembly yields a mid‐IR detector with high QE, fast readout (>85 Hz), large well depth (>1.2 million electrons), and linear readout. Longwave GeoSnap arrays would ideally be deployed on existing ground‐based telescopes as well as the next generation of extremely large telescopes. While employing advanced adaptive optics (AO) along with state‐of‐the‐art diffraction suppression techniques, instruments utilizing these detectors could attain background‐ and diffraction‐limited imaging at inner working angles <10 /D, providing improved contrast‐limited performance compared with JWST MIRI while operating at comparable wavelengths. We describe the performance characteristics of the 13‐m GeoSnap array operating between 38 45 K, including quantum efficiency, well depth, linearity, gain, dark current, and frequency‐dependent () noise profile.

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Development of a 2D precision cryogenic chopper for METIS

Cited by 2 publications

References 1 publication

VISIR upgrade overview and status

VISIR upgrade overview and status

Evaluating the GeoSnap 13‐μ$$ \mu $$m cutoff HgCdTe detector for mid‐IR ground‐based astronomy

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