The Update for S16B Applicants


Shared-risk Operation of MOIRCS

    Due to the MOIRCS Upgrade Project (nuMOIRCS Project: see below), MOIRCS is operated under the shared-risk policy during S16B Semester.

    We have completed the engineering observations for basic tests for both imaging and spectroscopy. Basic instrument performance is updated based on the engineering data, and is now available in the relevant page below.

    Basic Imaging performance is summarized in the Imaging section as well as the Instrument Parameter (especially in Detector Information Section) section. Please refer these pages.

    For spectroscopic performance, we now have significantly better sensitivity (up to 5 to 40% rise, better for blue band). With much lower readnoise (1/2 ~ 1/3 of the old system), we can reach the background-noise-limited performance for all available grisms. The overall spectroscopic performance is much better than old system. We expect you can enjoy the improved S/N of the data by the new system. As the data for deep spectroscopy is notPlease use the current performance for the observing time estimate.

For MOS Applicants

    When you apply the MOS observation, you must explicitly specify the required number of MOS masks (both for the Full and the Minimum Number of Nights) in the Section 16 (Instrument Requirement) of the application form. And also, please describe why you need the requested number in Section 14 (Technical Justification).

    The number of MOS mask will be fixed once it is assigned by TAC's critical reviewing. The request for backup MOS mask is basically not permitted, unless it is critical to the goal of the science. If you need backup mask, please make a clear justification on Section 14.

    Please note that the maximum number of MOS mask available for one contiguous observing period is 15.

Current Status of the MOIRCS Upgrade Project

Posted 2016-07-04

After the replacement of the detector to Hawaii2RG in late last year, we have completed some engineering observations for the chracterization by July 2016. The success of the first engineering observation was appeared in a Subaru Web Topic article.

We have confirmed that the new detectors and electronics provide a significant reduction in electronic noise in the data. The new detectors have 14 and 15 electrons respectively of read noise in a CDS frame, which is about a factor of 2 improvement compared with the old system. In multi-sampling exposures we confirmed that the readnoise reduces roughly proportional to the square-root of the multisampling. However, the degree of reduction slows relatively quickly at the number of multi-sampling larger than 20, possibly due to the ambient noise. In fact, we see some streak pattern across the slow-read direction in dark frame.

The new detectors have a better sensitivity than the old one, especially in Y and J bands. The rise of the sensitivity is from a few % (red side) to 27% (blue side). Note that the quantity largely depends on how you treat the QE variation across the detector.

The new system offers the 32-channel readout (cf. old system was 4 channel), which offers faster readout speed than the old system. The measured overhead time during a data acquisition, however, is about 15 sec. This is somewhat longer than expected, and we are still working on this.

Latent and inter-channel cross talk is quite low in channel-1 detector, while some degree of recognizable latent is seen for channel-2 image. We thus recommend to put high-priority target on channel-1 side.

The radiation hit events observed after replacement of the new detector was completely suppressed by the installation of a new alpha-paricle blocker window we have installed just after the last lens. A short report can be found here.

The spectroscopic performance was evaluated in April and May. Overall, the trend of the improvement is as expected from the imaging observation. The improvement of YJ band is quite impressive. Thanks to the reduced readout noise, we can reach the background-noise-limited performance in all grisms we have within reasonable amount of time. This has helped better subtraction of the sky, as we can keep the unit exposure time relatively short, This resulted in the better quality of the final spectra.

Future Plan

We are also planning to introduce the IFU spectroscopy function to MOIRCS, as well as the upgrade of the current MOS system. The date of the downtime is still TBD, though currently starting from early 2017, when MOIRCS might "hibernate" more than a year for possible SWIMS operation, is expected.

We will update the information via this website.


    !!! Caution !!!
    Some information on the current website are still for the old system before 2016. Be careful when you refer the number etc. Sorry for any inconvenience.

MOIRCS (Multi-Object InfraRed Camera and Spectrograph) provides wide-field imaging and long-slit/multi-object (MOS) spectroscopic capabilities in the 0.9 ~ 2.5 µm spectral range under the natural seeing condition. The 4'×7' field of view is covered by two Hawai-2 RG 2048×2048 infrared detector arrays with the spatial resolution of 0.116 arcsec/pixel.

For the imaging mode, the standard MKO YJHKs filters as well as some narrow-band filters are available. See the Imaging Mode Page for more details.

The MOS performance of MOIRCS spectroscopy mode is the most notable feature of the instrument. Using the cooled aluminium slit masks, MOIRCS can acquire 40 ~ 60 object spectra simultaneously across 0.9~2.5 micron wavelength range. The low-resolution (R~500) and high-resolution (R~3000) grisms are available (the R1300 medium-resolution grism is also available but have some issues). See the Spectroscopy Page for more details. All MOS observers/applicants should carefully read the MOS observation pages.

Instrument and Detector

Imaging mode

Spectroscopy mode

!! Note that much of the info here is still for OLD MOIRCS before 2016 !!

Instrument Citation

Please cite the following papers when you refer MOIRCS in your publication.
"Multi-Object Infrared Camera and Spectrograph (MOIRCS) for the Subaru Telescope I. Imaging"
Suzuki, R. et al. Publications of the Astronomical Society of Japan, 2008, Vol.60, No.6, pp.1347--1362.
"MOIRCS: Multi-Object Infrared Camera and Spectrograph for SUBARU"
Ichikawa, T. et al. 2006, in Proc. of SPIE, Vol. 6269, 38

MOIRCS Management Structure

  • Observation Support Astronomers
    • Primary: Dr. Ichi Tanaka (email: )
    • Secondary: Dr. Kentaro Aoki (email: )
  • Primary Instrument Operator / Documentation Responsible
    • Joshua Williams (email:
  • Data Distribution Resonsible
    • Tom Winegar and Computer Division (email:
  • Instrument Hardware and Software Resonsible
    • Instrument Division (email:
* Please change _AT_ to @ for email address.

Note that any data on the pages are subject to change.

Dr. Ichi Tanaka (MOIRCS Support Astronomer: email )

Updated 2016-01-19

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