GeminiFocus October 2014 | Page 15

GMOS Back for Science The Gemini Multi-Object Spectrograph (GMOS) is back at work for imaging, taking science data with the new Hamamatsu CCDs. As expected, the Hamamatsu CCDs are significantly more sensitive in the red, and appear to perform as advertised from the delivered QE curves pending final spectral throughput analysis. The new CCDs have also greatly reduced fringing, being now about 2 to 3 percent at 900 nanometers (compared to ~ 65 percent for the previous detectors). As you might recall, a decision was made in late 2012 to upgrade the GMOS-South detectors with the newly developed highly-sensitive CCDs manufactured by Hamamatsu Photonics. After an extensive period of testing in Hilo, the new detector array was shipped to Chile last April and installed in late May. The array then underwent commissioning during the following two months — including solving some electronics issues on the controllers. As of the start of Semester 2014B, the new CCDs are operating at full capacity. The screenshot (Figure 2) shows a direct comparison between i’-band imaging of the same field (previous E2V detector on the left, Ham- amatsu on the right). These raw, unprocessed images, should help you to appreciate the new CCDs’ great reduction in fringing. FLAMINGOS-2 Observations Start Observations for 2014B programs with FLAMINGOS-2 (F-2) have started, with a healthy distribution of 12 programs (Bands 1-3) across the partnership. The requested observing modes cover all the offered configurations: YJHKs imaging, and spectroscopy in five different spectral ranges. F-2 offers an average spectral resolution of 900 namometers for the spectral ranges JH and HK, and 2500 for J, H, and Ks. In July 2014, F-2 was back on-sky after two weeks of shutdown for repairing its decker wheel mechanism. Queue observations were resumed, guided with the telescope’s peripheral wavefront sensor. After the shutdown, the K-band internal background was found to be higher than normal in the HK spectroscopy mode, because the gate valve baffle was not positioning properly. Until a new instrument shutdown is programmed, the HK range spectroscopy observations of targets fainter than Ks ~ 16 have been put on hold. Figure 3. After having its decker wheel mechanism repaired, FLAMINGOS-2 is operational and working on several observing programs in the current semester. October 2014 GeminiFocus 13