Information for S20B applicants

Observations of IRCS-AO in S20B

IRCS + AO188 is only available with NGS mode in S20B. For detailed information, please carefully read the "Important Notice" of CfP website and AO188 website.

Please also check the current status of the instrument before preparing your proposal.

New narrowband filter for IRCS

A new narrowband filter created by Dr. Yusei Koyama (Subaru Telescope) will be installed. This filter will be available from the S20B semester under the shared-risk policy since it is currently under a performance evaluation by the observatory. Please see the "Available filters and sensitivities" page for further information.

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 SHOULD contact Dr. Tamura (; the PI of the waveplate unit). Please contact the primary support astronomer before submitting your proposal, for more detailed information including performance limitations. See "Polarimetry" section for basic information about polarimetry mode.


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 should contact to Dr. Tamura ( and the primary support astronomer for more detailed information if they have any plan of the 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.

January 30 2020

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