On-sky commissioning of Hamamatsu CCDs in GMOS-S

Abstract

GMOS-S has been recently upgraded with Hamamatsu deep depletion CCDs, replacing the original EEV detector array. The new CCDs have superior quantum efficiency (QE) at wavelengths longer than 680nm, with significant sensitivity extending beyond 1 micron. Furthermore, the fringing level in GMOS-S data is now much lower due to the much thicker CCDs, additionally improving delivered sensitivity above that afforded by quantum efficiency alone. Soon after the Hamamatsu CCDs were installed in June 2014, some issues were noticed that impacted the ability to execute some science programs. In October 2015 the ARC controller electronics were upgraded and a cable was replaced, and since November 2015 GMOS-S has again been taking science data with the Hamamatsu detectors with no sign of the previous limitations. We present the results of the GMOS-S on-sky commissioning of the Hamamatsu detector array, and provide an update on the status of the GMOS-N portion of the project.