Detector characteristics are given in this section. Note that the GMOS-North and GMOS-South detectors have different spectral responses, with GMOS-N having more red-sensitive CCDs and GMOS-S more blue-sensitive CCDs. Note also that the telescope optics are now silver-coated, reducing the system throughput in the blue.

The GMOS-North original EEV detectors were replaced with e2v deep depletion devices in October 2011, improving sensitivity in the blue and greatly improving / extending sensitivity to longer wavelengths. This interim upgrade is intended to be followed shortly afterward with a second upgrade featuring a new focal plane array populated with Hamamatsu devices, further improving red sensitivity, and including an upgraded detector controller. See the Status and Availability webpage for more details.

The recommended detector read-out configuration for all GMOS-N observations using the e2v DD detectors was anticipated to be

• slow read
• low gain
• 3 amplifiers

with the intent being to use the three best amplifiers, giving the lowest read-noise. This was the case for the original EEV detectors; however, for the new e2v DD detectors a recabling enacted to reduce spurious noise has yielded the 3 amplifiers mode unavailable. All GMOS-N data taken since November 22 has utilized 6-amp mode. A decision will be made soon as to whether or not efforts will be made to restore the 3-amplifier capability.

It is recommended not to use the fast read mode unless read-out speed is essential for the science goals of the program, i.e. time resolved observations. High gain is recommended only for programs that target very bright objects.

For the Hamamatsu detectors, we expect that the recommended detector read-out configuration will be

• slow read
• low gain
• 12 amplifiers

For the Hamamatsu detectors, the 6 amplifiers mode will be used only if one or more of the amplifiers delivers significantly greater read noise. The 3 amplifiers mode will not be available. Fast read-out speed will be available for time resolved observations and high gain for observations of very bright objects.