Figure 1.
Before (left) and after
(right) data from
GMOS-S showing
the banding present
before the fix (left)
and a different field
with bright stars after
the fix (right) with no
banding present.
The screenshots shown here (Figure 1) present examples of standard star fields with
bright stars using 2 x 2 binning before and after the board replacement. In the left image,
the banding effect is visible as dark lanes on
the saturated stars. In the right image, taken
after the fix, the effect is completely eliminated and saturated stars do not produce the
dark lanes.
Since the controller has changed, we are
now re-characterizing the entire detector
system, including re-measuring gains, read
noise, and full well for all modes. Meanwhile,
GMOS-S has resumed normal operation. We
found the primary science mode read noise
to be unchanged at ~ 4e-. A nice additional
benefit of this upgrade is that the full well increased by ~ 10 percent with respect to the
previous value.
operating at full capacity and are ready to deliver high-quality data to our users.
Having learned from these experiences, we are
building the GMOS-North Hamamatsu CCD
system with the new video controller boards
to avoid the banding problem entirely.
Gemini Instrument Feasibility
Studies (GIFS) Review
Each of the four GIFS proposal teams presented their draft study reports during meetings held at the Gemini North Base Facility
in late September. The teams will take the
feedback gathered from these meetings and
incorporate them into their final reports, due
in October. Figure 2 shows some of the excitement during the OCTOCAM report.
Figure 2.
Presentation by
Antonio de Ugarte
Postigo on the
OCTOCAM GIFS study
during a review of all
submitted Feasibility
Study reports in late
September 2015.
A second problem involving a charge
transfer smearing effect, most noticeable during long nod and shuffle sequences, has gone away on its own.
We have made several efforts to reproduce the problem, but the effects have
remained elusive, so we continue to
monitor. We will be investigating more
when we do some additional maintenance on GMOS-S in October. However, the bottom-line result is that the
Hamamatsu CCDs in GMOS-S are now
October 2015
GeminiFocus
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