The installation of fully-depleted Hamamatsu CCDs in GMOS-N in February/March 2017 marked the conclusion of the CCD upgrade project for the two Gemini Multi-Object Spectrographs. The corresponding upgrade for GMOS-S was completed in June/July 2014, so that both GMOS instruments are now operated with a detector array of three fully-depleted Hamamatsu CCDs. We present results from the commissioning of the GMOS-N Hamamatsu CCDs and discuss their on-sky performance. We provide a comparison of the GMOS-N and GMOSS detector parameters and summarize the main observing and data reduction strategies that apply to both detector arrays.
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.
Fighting vibrations on large telescopes is an arduous task. At Gemini, vibrations originating from cryogenic coolers have been shown to degrade the optical wavefront, in certain cases by as much as 40%. This paper discusses a general solution to vibration compensation by tracking the real time vibration state of the telescope and using M2 to apply corrections. Two approaches are then presented: an open loop compensation at M2 based on the signal of accelerometers at the M1 glass, and a closed loop compensation at M2 based on optical measurements from the wave front sensor. The paper elaborates on the pros and cons of each approach and the challenges faced during commissioning. A conclusion is presented with the final results of vibration tracking integrated with operations.
We report the results of a multi-year program to measure the vibration characteristics of the two Gemini telescopes. Measurements with fast-guiding wavefront sensors and networks of accelerometers show a correlation between image motion and optical vibrations induced mostly by instrument cryocoolers. We have mitigated the strongest vibrations by fast-guiding compensation and active cancellation of vibration sources.
Both Gemini telescopes, in Hawaii and Chile, are located in highly seismic active areas. That means that the seismic protection is included in the structural design of the telescope, instruments and auxiliary structure. We will describe the specific design features to reduce permanent damage in case of major earthquakes. At this moment both telescopes have been affected by big earthquakes in 2006 and 2015 respectively. There is an opportunity to compare the original design to the effects that are caused by these earthquakes and analyze their effectiveness.<p> </p> The paper describes the way the telescopes responded to these events, the damage that was caused, how we recovered from it, the modifications we have done to avoid some of this damage in future occasions, and lessons learned to face this type of events. Finally we will cover on how we pretend to upgrade the limited monitoring tools we currently have in place to measure the impact of earthquakes.
The real-time control systems for the Gemini Telescopes were designed and built in the 1990s using state-of-the-art
software tools and operating systems of that time. Since these systems are in use every night they have not been kept upto-
date and are now obsolete and very labor intensive to support. Gemini is currently engaged in a major upgrade of its
telescope control systems. This paper reviews the studies performed to select and develop a new standard operating
environment for Gemini real-time systems and the work performed so far in implementing it.
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.
The Gemini Observatory is continuing in the preliminary design stages of upgrading the micro-controller and related data acquisition components for the Secondary Mirror Tip/tilt System (M2TS). The Gemini North M2TS has surpassed a decade of service in the scientific community, yet the designs at both sites are nearly twenty years old and maintenance costs continue to increase. The next generation M2TS acquisition system takes a look at today's more common practices such as alternatives to VME, and the use of Industry Pack modules and high-rate data logging. An overview of the refactored software design will be described including the use of The Real-Time Executive for Multiprocessor Systems, or RTEMS, as the operating system of choice to meet the real-time performance requirements.
The Gemini Observatory is currently in the early stages of a major upgrade of the Secondary Mirror Tip/tilt Systems
(M2TS). Although these systems continue to deliver good fast-steering and chopping performance at both sites, there are
persistent and occasionally time-consuming issues that need to be addressed in order for them to deliver their full
potential and further reduce downtime. We present an overview of the system, outline its capabilities, and review the
early commissioning process and some of the issues encountered. We describe the augmentation of the original system
with data logging features which made possible some critical servo tuning work that was key in delivering improved
performance. The hardware and software upgrade project to date is discussed, along with a brief overview of items it
intends to address.
The Gemini Secondary Mirror Tip/tilt Systems (M2TS) have greatly benefited from the availability of software-based
data logging-to-disk of internal variables at servo loop rates, enabling efficient testing and troubleshooting. Similar 'fast-logging-to-disk' systems are now being considered for other Gemini subsystems. We describe how this technique was
successfully applied to the M2TS, solving intractable tuning problems; a forward look will show how extensive and fully integrated logging and diagnostic capabilities are at the heart of the new design for the M2TS-2. Designers of new and
ever-larger and more complex telescope systems are challenged to consider the benefits of including such systems in
their own designs at an early stage - and to consider the costs in terms of ease of performing diagnostics and loss of
maintainability of not doing so.
UIST is a facility class near-infrared instrument recently commissioned at the UK Infrared Telescope (UKIRT). UIST provides a comprehensive imaging and spectroscopic facility with spatial resolution limited only by the delivered tip-tilt corrected seeing. In addition to long slit spectroscopic modes, UIST includes the first deployable cryogenic integral field unit in a common user instrument. We will present results obtained during the commissioning period in late 2002. These include measurements of the image quality and the sensitivities of the different observing modes of the instrument. We also discuss the use of an instrument-specific telescope pointing-model developed for UIST to allow the instrument to meet the stringent flexure requirements arising from the choice of 0.06arcsec/pixel and 0.12arcsec/pixel plate scales. We pay particular attention to the performance of the image slicing integral field unit (IFU). We will present astronomical results from the first year of UIST operations, during which time UIST carried out diverse programmes, from mineralogical studies of Mars to measuring the mass of the black hole at the centre of the most distant quasar.