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.
A new technique has been developed to collimate the Gemini telescopes using the Peripheral Wavefront Sensors (PWFS) to measure focal plane offset and tilt. For several years prior to 2014, observers at Gemini North noticed a variation in the focus Zernike term of about ±30 μm when guiding with the PWFS. It was speculated that variation was due to a tilt of the PWFS rotary table. Further testing revealed that it was actually due to an incorrect tilt of the secondary mirror (M2), causing the focal plane to be offset and tilted relative to the PWFS axis. Due to the Ritchey- Chrétien design of the telescopes there is no Seidel comatic field pattern typical of an aligned telescope. Instead a constant comatic field pattern occurs from either tilt or decenter of M2, and patterns arising from tilt can be eliminated with the appropriate decenter. For the Gemini telescopes, proper alignment is not guaranteed from a zero-coma condition. The new technique measures PWFS focus variation around the periphery of the imaging field, 6 arcminutes off-axis, by programming the telescope pointing to move in a circle while PWFS tracks a guide star, completing a full circle. The measured focus variation is then used to calculate M2 tilt. The tilt and decenter offset are then adjusted to zero both focus variation and coma and achieve collimation. The technique permits correction of the erroneous M2 tilt to <~ 30 arcseconds, corresponding to a wavefront error <~ 3 μm, but is limited by short-period focus variations.
Gemini Observatory on Maunakea has been collecting optical and infrared science data for almost 15 years. We have begun a program to analyze imaging data from two of the original facility instruments, GMOS and NIRI, in order to measure sky brightness levels in multiple infrared and optical broad-band filters. The present work includes data from mid-2016 back through late-2008. We present measured background levels as a function of several operational quantities (e.g. moon phase, hours from twilight, season). We find that airglow is a significant contributor to background levels in several filters. Gemini is primarily a queue scheduled telescope, with observations being optimally executed in order to provide the most efficient use of telescope time. We find that while most parameters are well-understood, the atmospheric airglow remains challenging to predict. This makes it difficult to schedule observations which require dark skies in these filters, and we suggest improvements to ensure data quality.
The Gemini Remote Access to CFHT ESPaDONS Spectrograph has achieved first light of its experimental phase in May
2014. It successfully collected light from the Gemini North telescope and sent it through two 270 m optical fibers to the
the ESPaDOnS spectrograph at CFHT to deliver high-resolution spectroscopy across the optical region. The fibers gave
an average focal ratio degradation of 14% on sky, and a maximum transmittance of 85% at 800nm. GRACES achieved
delivering spectra with a resolution power of R = 40,000 and R = 66,000 between 400 and 1,000 nm. It has a ~8%
throughput and is sensitive to target fainter than 21st mag in 1 hour. The average acquisition time of a target is around 10 min. This project is a great example of a productive collaboration between two observatories on Maunakea that was
successful due to the reciprocal involvement of the Gemini, CFHT, and NRC Herzberg teams, and all the staff involved
closely or indirectly.
The GMOS-N instrument was upgraded with new CCDs in October 2011, improving the instrument sensitivity at both red and blue wavelengths. The deep depletion devices are manufactured by e2v (42-90 with multi-layer 3 coating) and extend the useful wavelength range of GMOS-N to 0.98 microns (compared to 0.94 microns previously). These detectors also exhibit much lower fringing than the original EEV detectors that had been in use since GMOS-N was commissioned in 2002. All other characteristics of the new detectors (readout speed, pixel size and format, detector controller, noise, gain) are similar to the original CCDs. Operating the new detectors in all amps mode (2 per CCD) has effectively improved the readout speed by a factor of 2. The new devices were selected to provide a quick and relatively simply upgrade route while technical issues with the Hamamatsu devices, originally planned for the upgrade, were investigated and resolved. We discuss the rationale for this interim upgrade, the upgrade process and attending issues. The new detectors have been used for science since November 2011. We present commissioning results illustrating the resulting gain in sensitivity over the original detector package. Gemini is still committed to installing Hamamatsu devices, which will further extend the useful wavelength range of GMOS to 1.03 microns, in both North and South GMOS instruments. We discuss the status of the Hamamatsu project and the current planned schedule for these future upgrades.
Target of opportunity observations (ToO) are an integral part of multi-instrument queue operations at Gemini
Observatory. ToOs comprise a significant fraction of the queue (20-25% of the highest ranking band) and with the
advent of large survey telescopes (eg. Pan-STARRS, LSST) dedicated to searching for transient events this fraction may
reasonably be expected to increase significantly in the coming years. While some important aspects of ToO execution at
Gemini Observatory are managed automatically (eg. trigger alerts, data distribution), other areas such as duplications
checking, scheduling and relative priority determination still require manual intervention. In order to increase efficiency
and improve our commitment to ToOs and queue observing in general, these aspects need to be formalized and
incorporated into improved phase 2 checking, automated queue scheduling and on-the-fly nightly plan generation
software. We discuss the different flavors of ToOs supported at Gemini Observatory and how each kind is scheduled
with respect to existing queue observations. We present ideas for formalizing these practices into a system of dynamical
prioritization which automatically self adjusts as new ToO observations are triggered, high priority targets become
endangered, and timing windows near expiration.
The Gemini Multi-Object Spectrograph (GMOS-N), with a field of view of
5.5 × 5.5 arc minutes, was used to obtain r' band images of the
Keck II laser beam. The data samples the Rayleigh scattered laser beam at low
elevations and the sodium spot at the highest elevation. The Rayleigh scattered part of
the beam is large at low elevations, filling the GMOS-N field of view, with high surface
brightness. At higher elevations (85 deg - 89.5 deg) it gets smaller and fainter. We also
present data taken on the laser spot which we see at an elevation of 89.625,
corresponding to a height in the atmosphere of ~100km. In addition, GMOS-N spectra
and GMOS-N on-instrument wavefront sensor (OIWFS) data have been collected that
allow us to characterize the effect that lasers from other telescopes might have on
GMOS-N data. The OIWFS works at wavelengths which include the sodium D band.
We present plans for the commissioning of the new GMOS-N red-sensitive science detectors, currently being integrated
into a new focal plane assembly at the NRC HIA. These Hamamatsu CCDs provide significantly higher quantum
efficiency than the existing detectors at red optical wavelengths (longward of ~ 700 nm), with > 80% QE at 900 nm
falling to ~10% QE at 1.05 μm. This upgrade not only improves current operations with GMOS-N, but also opens new
spectral ranges and potential observing modes (eg. use with Altair, the Gemini-N AO module). Care has been taken to
ensure that Nod & Shuffle will still be supported, since accurate sky subtraction is increasingly important at longer
wavelengths due to the increased density of sky lines. The commissioning plan aims to demonstrate the improvement in
current modes while minimizing the period of GMOS-N downtime for science use. The science commissioning is
currently scheduled for mid-November 2010.
The Gemini Observatories primarily operate a multi-instrument queue, with observers selecting observations that are best suited to weather and seeing conditions. Queue operations give higher ranked programs a greater chance for completion than lower ranked programs requesting the same conditions and instrument configuration. Queue observing naturally lends itself to Target of Opportunity (ToO) support since the time required to switch between programs and instruments is very short, and the staff observer is trained to operate all the available instruments and modes. Gemini Observatory has supported pre-approved ToO programs since beginning queue operations, and has implemented a rapid (less than 15 minutes response time) ToO mode since 2005. We discuss the ToO procedures, the statistics of 2+ years of rapid ToOs at Gemini North Observatory, the science that this important mode has enabled, and some recent software modifications which have improved both standard and rapid ToO support in the Gemini Observing Tool.
Gamma-ray bursts and other targets of opportunity require a quick response by observers to maximize the significance of observations. Because of this need for quickness, these types of observations are often observed at smaller facilities where observers and institutions have more freedom to respond to serendipitous events. The two Gemini 8-m telescopes have a well-developed workflow for queue observing that allows investigators to be involved in their science program throughout its lifecycle. To coincide with the startup of the Swift Gamma Ray Burst Explorer orbiting observatory in late 2004, the Gemini observing policies, workflow, and observing tools were enhanced to allow investigators to participate in target of opportunity programs. This paper describes how target of opportunity has been integrated into Gemini operations to allow investigators to trigger observations at the Gemini telescopes within minutes of an event.
We present the final results of the injection tests of adaptive optics corrected light into single mode fibers, conducted at Canada-France-Hawaii Telescope, W.M. Keck Observatory and Gemini North Observatory, in the prospect of 'OHANA Phase I (preparatory phase). We emphasize on the impact of the results on both the 'OHANA Phase II (interferometric demonstration phase) sensitivity and observational protocol and the behavior of the different adaptive optics.
The Mauna Kea Observatory offers a unique opportunity to build a large and sensitive interferometer. Seven telescopes have diameters larger than 3 meters and are or may be equipped with adaptive optics systems to correct phase perturbations induced by atmospheric turbulence. The maximum telescope separation of 800 meters can provide an angular resolution as good as 0.25 milli-arcseconds in the J band. The large pupils and long baselines make 'OHANA very complementary to existing large optical interferometers. From an astrophysical point of view, it opens the way to imaging of the central part of faint and compact objects such as active galactic nuclei and young stellar objects. On a technical point of view, it opens the way to kilometric or more arrays by propagating light in single-mode fibers. First instruments have been built and tested successfully at CFHT, Keck I and Gemini to inject light into single-mode fibers thus partly completing Phase I of the project. Phase II is now on-going with the prospects of the first combinations of Keck I - Keck II in 2004 and Gemini - CFHT in 2005.
The Far Ultraviolet Spectroscopic Explorer (FUSE) satellite was launched into orbit on June 24, 1999. FUSE is now making high resolution ((lambda) /(Delta) (lambda) equals 20,000 - 25,000) observations of solar system, galactic, and extragalactic targets in the far ultraviolet wavelength region (905 - 1187 angstroms). Its high effective area, low background, and planned three year life allow observations of objects which have been too faint for previous high resolution instruments in this wavelength range. In this paper, we describe the on- orbit performance of the FUSE satellite during its first nine months of operation, including measurements of sensitivity and resolution.