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GMOS-North Detectors

The GMOS detector array consists of three 2048x4608 EEV chips arranged in a row. The table below gives a summary of the current detector/controller characteristics.

Array	EEV
Pixel format	6144x4608 pixels
Array layout	Three 2048x4068 chips in a row with ~0.5mm gaps
Pixel size	13.5 microns square; 0.0727 arcsec/pixel
Spectral Response	approx 0.3 to 0.9 microns [ data / plot ]
Bias level	Bias image
Flat field response	Fringe images Flat field images
Readout time	See observing overheads page
Chip	CCD 01	CCD 02	CCD 03
Chip ref no.	EEV 9273-16-03	EEV 9273-20-04	EEV 9273-20-03
Dark current*	0.8 e-/pix/hr	0.7 e-/pix/hr	0.5 e-/pix/hr
Full Well **	150 ke-	101 ke-	159 ke-
Fringing at 900nm ***	29%	19%	24%

* Dark current measured at -120C by NOAO
** Saturation can be avoided by assuming 100ke- for all chips
*** (peak-valley)/mean, measured from images taken at NOAO

Readnoise and Gain Values

The table below gives gain/read-noise values for the current GMOS EEV CCDs operating with the SDSU controller. Only the suggested settings are listed. The values are averaged over all 6 amps. For the full table of read-noise and gain values at all settings and for all amps, click here .

Readout	Gain	Resulting average
rate	level	Gain (e-/DN)	noise (e- rms)
Fast	High	5.02	7.4
"	Low	2.49	4.9
Slow	High	4.40	4.8
"	Low	2.18	3.4

Data Format

Each of the three chips can be read out through one or two amplifiers (left and right). In the two-amplifier mode the output data file then contains 6 fits extensions (see diagram below). Each of the six image sections has an accompanying overscan region 32 pixels wide. In one-amp mode the data file contains three extensions, one per chip, again with a 32-pixel wide overscan section. The one-amplifier mode is the most used for science applications.

More information about the data format and GMOS data examples are available.

Binning: When pixel binning is used, the resulting datafile still contains overscan regions that are 32 samples wide.

Layout of GMOS detector array and structure of the output data file, when reading out in 6-amp mode, with unbinned pixels.

Layout of GMOS detector array and structure of the output data file, when reading out in 3-amp mode (using the 'best' three amps, R,R,L). Note the overscan regions are not in the same place for each chip.

In original form: Isobel Hook
Last update: March 30, 2006; Kathy Roth