MOIRCS Instrument Parameters

Detectors(10)HAWAII-2 RG Science Grade x 2
Sci#16926 (channel 1) and Sci#16843 (Channel 2)
Pixel size18 um
Pixel scale(1)0.116''
Field of view3.9' x 6.9' (2)
Gain(3)2.07 e-/ADU (ch1), 1.99 e-/ADU (ch2)
Dark current< 0.01 e-/s
Saturation level~65k ADU (4)
Read noise15 e- rms(5)
Number of amplifiers per detector32
Minimum Exposure(6) (sec)1.475*NDR (NDR=1 for normal CDS data)
Overhead of repeated readout(7)~12.5+1.475*NDR (sec)
Filter exchange time 15~60 sec
Number of available mask slotsup to 21 (15 for users)
Typical number of slits per mask(8)40~60
Days needed for cooling mask 2 whole days
MOS aquisition time(9) about 20 min

(1) The value measured around the center of the raw image. Note that the pixel scale becomes smaller with the distance from the optical center due to the optical distortion (barrel distortion).

(2) Hawaii-2 RG detector has 2040 x 2040 sensitive pixels, with the additional 4 rows and columns of "reference pixels" on each side (see Detector Information). About 0.4 arcmin2 region at the upper right of the channel-2 raw image is vignetted by the calprobe box in the Cs frange unit. Please see the FOV page. And also, the mosaic boundary between channels (~0.4 arcmin2) is not usable for science.

(3) Measured values in April 2016 using the final Readout Parameters setting by the photon transfer method. Though the nominal error is 1%, somewhat more systematics may exists. Note that this is after the inter-pixel crosstalk correction (6%) is applied.

(4) The value is under the single readout data (fits extension data 2). The pedestal level is each 7k and 8k (ADU) for ch1 and 2, respectively. Note that the ~5% non-linearity level is reached at about 45k and 60k ADU for ch1 and 2 in single readout, respectively. We recommend to keep the maximum counts less than 25000 ADU in CDS data to achieve < 2 % non-linearity level.

(5) Under the single CDS (NDR=1). The value under the multi-sampling (NDR) reduce the noise by sqrt(NDR), though the reduction somewhat slows down at NDR > 20 (possibly due to some ambient noise: TBD).

(6) In future we will introduce the "Window mode" (partial-readout mode) to enable much faster data acquisition.

(7) Typical value with a few seconds of variation. Note that the value does not include the time related to the telescope move. See the Overhead Part in "Guide to exposure time" webpage for more.

(8) Maximum number is under the length of slitlets of 7.5 arcseconds. See the MOS section for more about the choice of slit length.

(9) See also the MOS page. The acquisition time for Long slits can be similar or a bit shorter than this.

(10) We are using the Cryogenic Focal Plane Electronics SIDECAR ASIC #40 for channel 1, and #39 for channel 2.

FITS file format and Header Keywords

We use the Multi-Extension FITS (MEF) format since 2016. The primary header and its data are the CDS data and usuallly used for your science. The extension 1 is the "reset level (or "pedestal") image", i.e., the image just after the reset, and the extension 2 is the "signal image", the image after the exposure time. The CDS frame is made by subtracting the reset level data from the signal level data, as well as the bias level correction using the "reference pixel" regions. If you use the multi-sampling readout, the same number of reset level images and signal level images as multi-sampling number is attached. See also the "Detector information" Page for more.

For the fits information for the old moircs, please visit the old page below.

Old MOIRCS Information

For reference, the old page can be found here.

Please note that all data on these pages are subject to change as the evaluation of the performance of the upgraded MOIRCS progresses.

Updated 2016-07-06

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