The Infrared Imaging Spectrograph (IRIS): project status report

Warad, Kanaka; Andersen, David; Larkin, James E.; Wright, Shelley; Weber, Robert W.; Suzuki, Ryuji; Kupke, Renate; Dunn, Jennifer; Atwood, Jenny; Skidmore, Warren; Miles, John; Nakamoto, Takashi

doi:10.1117/12.3020699

Ground-Based and Airborne Instrumentation for Astronomy X 2024

DOI: 10.1117/12.3020699

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The Infrared Imaging Spectrograph (IRIS): project status report

Kanaka Warad,

David Andersen,

James E. Larkin

et al.

Abstract: The Infrared Imaging Spectrograph (IRIS) is a diffraction-limited instrument designed for the Thirty Meter Telescope (TMT) through an international collaboration. IRIS works in tandem with the Narrow-Field InfraRed Adaptive Optics System (NFIRAOS) and covers a near-infrared spectral range of 0.84 to 2.4 microns. IRIS and NFIRAOS will be the instruments used to demonstrate first light at TMT. IRIS incorporates a wide-field Imager with a fixed plate scale of 4 milliarcseconds (mas), and an Integral Field Spectro… Show more

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Cited by 2 publications

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Petalling mode sensing for the Thirty Meter Telescope

Wang,

Schoeck,

Véran

et al. 2024

Adaptive Optics Systems IX

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Petalling modes characterize the differential piston between the petals of the telescope's aperture, typically separated by the secondary mirror support spiders. Since the discovery of petalling modes by the VLT in low wind conditions, addressing these modes has become a focal point, pertinent to nearly all telescopes equipped with high-performance adaptive optics systems. These modes are poorly sensed by mainstream wavefront sensors (WFS). There are three primary factors contributing to petalling modes in general. Firstly, turbulence discontinuity occurs across the spiders due to temperature non-uniformity, particularly in low wind conditions. This issue is partly mitigated by applying low emissivity coating, pioneered by the VLT. Computational fluid dynamics models used to assess the dome seeing aid in quantifying the residual effect. Secondly, phasing and stacking errors may arise in segmented mirrors. For TMT, the impact is negligible owing to the small width of the support spiders (22.5 cm) and highly redundant phasing sensors in the Alignment and Phasing System. Lastly, measurement noise may propagate to these modes, which we have observed when controlling two deformable mirrors in classic adaptive optics (AO) mode with a single pyramid WFS. Employing modal control with truncated modes is a simple and effective mitigation strategy without a notable performance penalty. Nevertheless, having a mechanism that can measure and control the petalling modes will provide reassurance of the AO system's performance. In this paper, we present a novel hybrid iterative petalling sensor (HIPS) that utilizes modal based phase retrieval on time averaged PSFs from diffraction-limited tip/tilt/focus and full aperture low-order wavefront sensors, which breaks the even mode ambiguity. We successfully demonstrated this algorithm in both static and end-to-end closed-loop AO simulations.

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Petalling mode sensing for the Thirty Meter Telescope

Wang,

Schoeck,

Véran

et al. 2024

Adaptive Optics Systems IX

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Liger at W.M. Keck Observatory: overall design and science drivers

Wright,

Jones,

Larkin

et al. 2024

Ground-Based and Airborne Instrumentation for Astronomy X

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Liger is a next-generation near-infrared (0.81 -2.45 µm) integral field spectrograph (IFS) and imaging camera for the W. M. Keck Observatory (WMKO) adaptive optics (AO) system. The instrument concept originated by coupling designs from WMKO AO instruments and the future Thirty Meter Telescope IRIS spectrograph. Liger is designed for the Keck I telescope to operate behind the upcoming Keck All-sky Precision Adaptive optics (KAPA) system. The imaging camera sequentially feeds an IFS that makes use of slicer assembly for the coarsest sampling (75 mas and 150 mas per spaxel) and lenslet array (14 mas and 31 mas per spaxel) for diffraction-limited sampling. The imaging camera makes use of off-axis parabolas and a Hawaii-2RG detector to achieve a 14 mas/pixel plate scale and 20.5"×20.5" field of view. The IFS offers a range of spectral resolving power of R=4,000 -10,000 and yields large fields of view for an AO-fed IFS. Liger will enable new science by providing enhanced capabilities, including higher spectral resolving power, access to shorter wavelengths, and larger fields of view than any current or planned ground-or space-based IFS system. Liger will be able to unlock previously inaccessible science across a wide range of the cosmos, such as dark matter substructure, supermassive black holes, the Galactic Center, exoplanet atmospheres, and the time-variable Solar System. We present the overall design of the Liger subsystems and review unique science drivers.

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The Infrared Imaging Spectrograph (IRIS): project status report

Cited by 2 publications

References 22 publications

Petalling mode sensing for the Thirty Meter Telescope

Petalling mode sensing for the Thirty Meter Telescope

Liger at W.M. Keck Observatory: overall design and science drivers

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