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