Information for S24A applicants

LGS mode will be operated with TBAD (Shared-risk)

The new laser guide star (LGS) system for AO188 will be operated with TBAD (Transponder Based Aircraft Detector). Please note that the LGS mode with TBAD will be opened as a shared-risk policy. All proposals requesting LGS mode observation should prepare a backup plan with NGS mode. Please carefully read the AO188 webpage for additional information of the new laser system.

Near-Infrared wavefront sensor for AO188 (Shared-risk)

The near-infrared wavefront sensor (NIR WFS) is available for IRCS 20 mas imaging and echelle observations. Please carefully read the IRCS + NIR WFS webpage for the available modes, sensitivities, and restrictions. Users planning to submit a proposal MUST contact Dr. Julien Lozi (; the PI of the NIR WFS) and include him in the proposal as a Co-I.

Polarimetry mode (Shared-risk)

IRCS provides several linear polarimetry modes in 0.95−4.80 μm as 'Shared-Risk' mode. Users who want to propose polarimetry observation MUST contact Dr. Tamura (; the PI of the NsIR waveplate unit) and include him in the proposal as a Co-I. In addition, contact the support astronomer before submitting your proposal. See "Polarimetry" section for basic information about polarimetry mode.

Other general informations

Please see the general informaion of IRCS + AO188 before preparing your proposal.
Also, please check the current status of IRCS.


The Infrared Camera and Spectrograph (IRCS) is installed at the Infrared Nasmyth focus of Subaru Telescope and incorporates two 10242 ALADDIN III arrays which are sensitive from 0.9−5.6 μm. IRCS is designed to deliver diffraction limited images from 2 μm and up, as well as providing spectroscopy with grisms and a cross-dispersed echelle. The camera can also be used as a slit viewer for the echelle spectroscopy.

IRCS is always operated with Adaptive Optics (AO188) attached regarldess of using adaptive optics, and relies on AO188 for guiding without a separate autoguider.


The imaging mode of IRCS provides two plate scales, of 20 and 52 mas per pixel, producing fields of view of 21'' and 54'', respectively. The camera is equipped with a range of broad and narrow-band filters in its three filter wheels.

Grism spectroscopy

The camera section of IRCS provides a number of grisms which provide a low resolution (R = 100-2000) spectroscopic capability. Slit widths of 0.1-0.9'' are available.

Echelle spectroscopy

IRCS has a cross-dispersed echelle spectrograph, providing spectral resolution up to 20 000. The IRCS echelle provides a pixel scale of 55 mas along the slit and slit widths of 0.14'', 0.27'' (providing half the spectral resolution), or 0.54'' (providing one-quarter the spectral resolution). The camera-side detector is used as a slit viewer.

Note: We provide an NH3 gas absorption cell function for a high-precision radial velocity measurement at the 30 m s-1 level even with the spectral resolving power of IRCS. The NH3 gas cell can be used in a part of K-band with IRCS + AO188 mode. Please contact to IRCS + AO188 support astronomer for further information. The IR gas cell was provided by Andreas Seifahrt (University of Chicago) in collaboration with colleagues at the university of Goettingen (Germany) and Lund Observatory (Sweden).


IRCS provides several linear polarimetry modes in 0.95−4.80 μm as 'Shared-Risk' mode. Imaging polarimetry is available for Y-, J-, H-, K(K')-, L'-, and M'-bands. Spectropolarimetry is available with zJH-, HK-, K-, and L-grisms in 52 mas mode only. Please be advised that circular polarimetry is not available. Users must contact Dr. Tamura ( and the primary support astronomer if they are planning to submit any kind of proposal with polarimetry mode observation.

Observation Preparation


When referring to IRCS in a paper, please use the following citation. The papers can be downloaded from links below.

Further information


Questions regarding IRCS should be directed to the primary support astronomer (Yuhei Takagi,

Please note that all numbers on these pages are subject to change as the performance of IRCS is better determined.

Jul 28 2023

© 2000 Subaru Telescope, NAOJ.