The Giant Magellan Telescope (GMT)1 is a 25 m telescope composed of seven 8.4 m “unit telescopes”, on a common mount. Each primary and conjugated secondary mirror segment will feed a common instrument interface, their focal planes co-aligned and co-phased. During telescope operation, the alignment of the optical components will deflect due to variations in thermal environment and gravity induced structural flexure of the mount. The ultimate co-alignment and co-phasing of the telescope is achieved by a combination of the Acquisition Guiding and Wavefront Sensing system (AGWS) and two segment-edge-sensing systems2. An analysis of the capture range of the AGWS indicates that it is unlikely that that system will operate efficiently or reliably with initial mirror positions provided by open-loop corrections alone3.
Since 2016 GMT have been developing a telescope metrology system, that is intended to close the gap between openloop modelling and AGWS operations. A prototyping campaign was initiated soon after receipt of laser metrology hardware in 2017. This campaign is being conducted in collaboration with the Large Binocular Telescope Observatory (LBTO), and hardware was first deployed on the LBT in August 2017. Since that time the system had been run and developed over some hundreds of hours on-sky. It has been shown to be capable of reliably measuring the relative positions of the main optics over ~ 10 m to a repeatability of ~ 1-2 microns RMS. This paper will describe the prototyping campaign to date, the basic design of the system, lessons learned and results achieved. It will conclude with a discussion of future prototyping efforts.
The Giant Magellan Telescope (GMT) is a 25-meter extremely large telescope that is being built by an international
consortium of universities and research institutions. Its software and control system is being developed using a set of
Domain Specific Languages (DSL) that supports a model driven development methodology integrated with an Agile
management process. This approach promotes the use of standardized models that capture the component architecture of
the system, that facilitate the construction of technical specifications in a uniform way, that facilitate communication
between developers and domain experts and that provide a framework to ensure the successful integration of the
software subsystems developed by the GMT partner institutions.
The Gemini Multi-Conjugate Adaptive Optics System (GeMS) began its on-sky commissioning in January 2011.
The system provides high order wide field corrections using a constellation of five Laser Guide Stars. In December 2011, commissioning culminated in images with a FWHM of 80±2mas at 1.65 microns (H band) over an 87 x 87 arcsecond field of view. The first images have already demonstrated the scientific potential of GeMS, and after more than a year of commissioning GeMS is finally close to completion and ready for science. This paper presents a general status of the GeMS project and summarizes the achievements made during more than a year of commissioning. The characterization of GeMS performance is presented in a companion paper: “GeMS on-sky results”, Rigaut et al. Here we report on the sub-systems' performance, discuss current limitations and present proposed upgrades. The integration of GeMS into the observatory operational scheme is detailed. Finally, we present the plans for next year's operations with GeMS.
The Giant Magellan Telescope Organization is designing and building a ground-based 25-meter extremely large telescope. This project represents a significant increase in complexity and performance requirements over 8-10 meter class telescope control systems. This paper presents how recent software and hardware technologies and the lessons learned from the previous generation of large telescopes can help to address some of these challenges. We illustrate our model-centric approach to capture all the functionalities and workflows of the observatory subsystems, and discuss its benefits for implementing and documenting the software and control systems. The same modeling approach is also used
to capture and facilitate the development process.
The Gemini Multi-Conjugate Adaptive Optics System (GeMS} began its on-sky commissioning in January 20ll. The system provides high order wide-field corrections using a constellation of five Laser Guide Stars. In December 20ll, commissioning culminated in images with a FWHM of 80±2mas at 1.65 microns (H band} over an 87 x 87 arcsccond field of view. The first images have already demonstrated the scientific potential of GeMS, and after more than a year of commissioning GeMS is finally close to completion and ready for science. This paper presents a general status of the GeMS project and summarizes the achievements made during more than a year of commissioning. The characterization of GeMS performance is presented in a companion paper: "GeMS on-sky results" , R.igaut ct al. Here we report on the sub-systems' performance, discuss current limitations and present proposed upgrades. The integration of GeMS into the observatory operational scheme is detailed. Finally, we present the plans for next year's operations with GeMS.
With two to three deformable mirrors, three Natural Guide Stars (NGS) and five sodium Laser Guide Stars (LGS), the
Gemini Multi-Conjugate Adaptive Optics System (Gemini MCAO a.k.a. GeMS) will be the first facility-class MCAO
capability to be offered for regular science observations starting in 2013A. The engineering and science commissioning
phase of the project was kicked off in January 2011 when the Gemini South Laser Guide Star Facility (GS LGSF)
propagated its 50W laser above the summit of Cerro Pachón, Chile. GeMS commissioning has proceeded throughout
2011 and the first half of 2012 at a pace of one 6- to 10-night run per month with a 5-month pause during the 2011
This paper focuses on the LGSF-side of the project and provides an overview of the LGSF system and subsystems, their
top-level specifications, design, integration with the telescope, and performance throughout commissioning and beyond.
Subsystems of the GS LGSF include: (i) a diode-pumped solid-state 1.06+1.32 micron sum-frequency laser capable of
producing over 50W of output power at the sodium wavelength (589nm); (ii) Beam Transfer Optics (BTO) that transport
the 50W beam up the telescope, split the beam five-ways and configure the five 10W beams for projection by the Laser
Launch Telescope (LLT) located behind the Gemini South 8m telescope secondary mirror; and (iii) a variety of safety
systems to ensure safe laser operations for observatory personnel and equipment, neighbor observatories, as well as
passing aircrafts and satellites.
GeMS, the Gemini Laser Guide Star Multi-Conjugate Adaptive Optics facility system, has seen first light in December 2011, and has already produced images with H band Strehl ratio in excess of 35% over fields of view of 85x85 arcsec, fulfilling the MCAO promise. In this paper, we report on these early results, analyze trends in performance, and concentrate on key or novel aspects of the system, like centroid gain estimation, on-sky non common path aberration estimation. We also present the first astrometric analysis, showing very encouraging results.
GeMS (the Gemini Multi-conjugated adaptive optics System) is a facility instrument for the Gemini-South
telescope. It will deliver a uniform, diffraction-limited image quality at near-infrared (NIR) wavelengths over an
extended FoV or more than 1 arcmin across. GeMS is a unique and challenging project from the technological
point of view and because of its control complexity. The system includes 5 laser guide stars, 3 natural guide
stars, 3 deformable mirrors optically conjugated at 0, 4.5 and 9km and 1 tip-tilt mirror. After 10 years since
the beginning of the project, GeMS is finally reaching a state in which all the subsystems have been received,
integrated and, in the large part, tested. In this paper, we report on the progress and current status of the
different sub-systems with a particular emphasis on the calibrations, control and optimization of the AO bench.
Myst is the Gemini MCAO System (GeMS) high level control GUI. It is written in yorick, python and C. In this
paper, we review the software architecture of Myst and its primary purposes, which are many: Real-time display,
high level diagnostics, calibrations, and executor/sequencer of high level actions (closing the loop, coordinating
CANOPUS is the facility instrument for the Gemini Multi Conjugate Adaptive Optics System (GeMS) wherein all the
adaptive optics mechanisms and associated electronic are tightly packed. At an early stage in the pre-commissioning
phase Gemini undertook the redesign and implementation of its chilled Ethylene Glycol Water (EGW) cooling system to
remove the heat generated by the electronic hardware. The electronic boards associated with the Deformable Mirrors
(DM) represent the highest density heat yielding components in CANOPUS and they are also quite sensitive to
overheating. The limited size of the two electronic thermal enclosures (TE) requires the use of highly efficient heat
exchangers (HX) coupled with powerful yet compact DC fans.
A systematic approach to comply with all the various design requirements brought about a thorough and robust solution
that, in addition to the core elements (HXs and fan), makes use of features such as high performance vacuum insulated
panels, vibration mitigation elements and several environment sensors. This paper describes the design and
implementation of the solution in the lab prior to delivering CANOPUS for commissioning.
As part of its Safe Aircraft Localization and Satellite Acquisition System (SALSA), Gemini is building an All Sky Camera (ASCAM) system to detect aircrafts in order to prevent propagation of the laser that could be a safety hazard for pilots and passengers. ASCAM detections, including trajectory parameters, are made available to neighbor observatories so they may compute impact parameters given their location. We present in this paper an overview of the system
architecture, a description of the software solution and detection algorithm, some performance and on-sky result.
We present Canopus, the AO bench for Gemini's Multi Conjugate Adaptive Optics System (GEMS), a unique facility for
the Gemini South telescope located at Cerro Pachon in Chile. The MCAO system uses five laser beacons in conjunction
with different natural guide stars configurations. A deployable fold mirror located in the telescope Acquisition and
Guiding Unit (A&G) sends the telescope beam to the entrance of the bench. The beam is split within Canopus into three
main components: two sensing paths and the output corrected science beam. Light from the laser constellation (589nm)
is directed to five Shack-Hartman wave front sensors (E2V-39 CCDs read at 800Hz). Visible light from natural guide
stars is sent to three independent sensors arrays (SCPM AQ4C Avalanche Photodiodes modules in quad cell
arrangement) via optical fibers mounted on independent stages and a slow focus sensor (E2V-57 back-illuminated
CCD). The infrared corrected beam exits Canopus and goes to instrumentation for science. The Real Time Controller
(RTC) analyses wavefront signals and correct distortions using a fast tip-tilt mirror and three deformable mirrors
conjugated at different altitudes. The RTC also adjusts positioning of the laser beacon (Beam Transfer Optics fast
steering array), and handles miscellaneous offloads (M1 figure, M2 tip/tilt, LGS zoom and magnification corrections,
NGS probes adjustments etc.). Background optimizations run on a separate dedicated server to feed new parameters into
The Gemini Observatory is implementing a Multi-Conjugate Adaptive Optics (MCAO) system as a facility instrument
for the Gemini South telescope (GeMS). The system will include 5 Laser Guide Stars, 3 Natural Guide Stars, and 3
deformable mirrors, optically conjugated at different altitudes, to achieve near-uniform atmospheric compensation over a
one arc minute square field of view. This setup implies some level of operational complexity.
In this paper we describe how GeMS will be integrated into the flow of Gemini operations, from the observing
procedures necessary to execute the programs in the queue (telescope control software, observing tools, sequence
executor) to the safety implementation needed such as spotters/ASCAM, space command and laser traffic control
The Gemini Observatory is in the final integration and test phase for its Multi-Conjugate Adaptive Optics (MCAO)
project at the Gemini South 8-meter telescope atop Cerro Pachón, Chile. This paper presents an overview and status of
the laser-side of the MCAO project in general and its Beam Transfer Optics (BTO), Laser Launch Telescope (LLT) and
Safety Systems in particular. We review the commonalities and differences between the Gemini North Laser Guide Star
(LGS) facility producing one LGS with a 10W-class laser, and its southern sibling producing five LGS with a 50W-class
laser. We also highlight the modifications brought to the initial Gemini South LGS facility design based on lessons
learned over 3 years of LGS operations in Hawaii. Finally, current integration and test results of the BTO and on-sky
LLT performance are presented. Laser first light is expected in early 2009.
The Gemini Multi-Conjugate Adaptive Optics project was launched in April 1999 to become the Gemini South
AO facility in Chile. The system includes 5 laser guide stars, 3 natural guide stars and 3 deformable mirrors optically
conjugated at 0, 4.5 and 9km to achieve near-uniform atmospheric compensation over a 1 arc minute square field of
Sub-contracted systems with vendors were started as early as October 2001 and were all delivered by July
2007, but for the 50W laser (due around September 2008). The in-house development began in January 2006, and is
expected to be completed by the end of 2008 to continue with integration and testing (I&T) on the telescope. The on-sky
commissioning phase is scheduled to start during the first half of 2009.
In this general overview, we will first describe the status of each subsystem with their major requirements, risk
areas and achieved performance. Next we will present our plan to complete the project by reviewing the remaining steps
through I&T and commissioning on the telescope, both during day-time and at night-time. Finally, we will summarize
some management activities like schedules, resources and conclude with some lessons learned.
Altair is the general-purpose Adaptive Optics bench installed on Gemini North that has operated successfully with
Natural Guide Star (NGS) since 2003. The original design and fabrication included an additional WaveFront Sensor
(WFS) to enable operation with Laser Guide Star (LGS). Altair has been recently upgraded and functional
commissioning was performed between June and November 2005. The insertion of a dichroic beamsplitter in the
NGS path allows to reflect the 589nm light to the LGS wavefront sensor and transmit the visible light of the NGS (or
Tip-Tilt Guide star -TTGS-) to the tip-tilt-focus sensors. We will review the various modifications made for this dual
operation, both in hardware and software, and describe the steps and results of the integration and testing phase on the