Gabriel Perez

Gemini multiconjugate adaptive optics system review - I. Design, trade-offs and integration

The Gemini multiconjugate adaptive optics system (GeMS) at the Gemini South telescope in Cerro Pachon is the first sodium-based multilaser guide star (LGS) adaptive optics system. It uses five LGSs and two deformable mirrors to measure and compensate for atmospheric distortions. The GeMS project started in 1999, and saw first light in 2011. It is now in regular operation, producing images close to the diffraction limit in the near-infrared, with uniform quality over a field of view of two square arcminutes. This paper is the first one in a two-paper review of GeMS. It describes the system, explains why and how it was built, discusses the design choices and trade-offs, and presents the main issues encountered during the course of the project. Finally, we briefly present the results of the system first light.

The Gemini MCAO System GeMS: nearing the end of a lab-story

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.

The Gemini South MCAO laser guide star facility: getting ready for first light

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.

GeMS: Gemini Mcao System: current status and commissioning plans

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 view. 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.

The Gemini MCAO infrastructure: laser service enclosure and support structure

The Laser Service Enclosure (LSE) is an environmentally controlled ISO 7 clean room designed to house, protect and provide environmental control for the Gemini South multi-conjugate adaptive optics laser system. The LSE is 8.0 meters long, 2.5 meters wide and 2.5 meters high with a mass of approximately 5,100 kg. The LSE shall reside on a new telescope Nasmyth platform named the Support Structure (SS). The SS is a three-dimensional beam and frame structure designed to support the LSE and laser system under all loading conditions. This paper will review the system requirements and describe the system hardware including optical, environmental, structural and operational issues as well as the anticipated impact the system will have on the current telescope performance.

Gemini all-sky camera for laser guide star operation

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.

Dueling lasers! A comparative analysis of two different sodium laser technologies on sky

Sodium guide star technologies for Adaptive Optics (AO) have been around for over 20 years. During this time, the technologies for the lasers used to excite the mesospheric sodium have been in constant development, with the goals being not only to excite as much sodium as possible, but to do so efficiently, while producing a round guide star, and while offering a reliable facility. The first lasers in use were dye lasers with a liquid gain medium, while these lasers were able to produce sodium guide stars, the liquid dye used was toxic and flammable. The second generation of guide star lasers used sum-frequency-mixed solid-state lasers. These lasers provided excellent return but were notoriously difficult to calibrate and maintain, requiring a full-time laser engineer on staff. The current third generation of sodium guide star lasers use Raman fiber amplification to generate a laser that is very efficient at exciting sodium with a good spot profile and offer a high degree of reliability. The Gemini South observatory for the last few years has been in the process of obtaining one of these third-generation lasers, a Toptica Sodium Star 20/2 while maintaining its second-generation Lockheed Martin Coherent Technologies (LMCT) 50W CW Mode-locked laser. In October of 2017 successful on-sky commissioning of the Toptica laser was executed while the LMCT laser was still active and in operations. During the course of the commissioning run both lasers were used on sky in close in time in possible. We present a comparative study of the performance of each laser.

Switching between two laser guide star facilities: an overview of the optomechanical design for the new laser beam injector at the Gemini South Observatory

A motorized laser Beam Injector Module (BIM) has been designed to integrate the new Toptica SodiumStar 20/2 laser to the Beam Transfer Optics (BTO) subsystem of the Gemini South telescope. The main goal is to inject the new laser beam co-axially to the BTO optical axis without altering the optical path of the current Lockheed Martin Coherent Technologies (LMCT) sodium laser. The optical design consists of a custom high-power attenuator offering two power modes, an opto-mechanical laser switch to commute between the two laser guide star facilities within a short period of time and a set of tip-tilt picomotor mirror mounts for BTO optical alignment. The motorized module is remotely controlled via an EPICS command interface by the laser operator that can propagate both lasers consecutively on sky for the measurement of the sodium layer guide star photon return. The laser beam factor quality and optical characteristics of the beam injector output beam have been measured within the Gemini South Laser Guide Star (GS-LGS) requirements. This paper presents a general overview of the new sodium laser facility and the beam injector optomechanical design. It reports on the optical calibration, laser beam characterization, telescope integration and BTO optical alignment.

An infusion of new blood using the Toptica laser with GeMS: results of the commissioning and science performance

Adaptive Optics (AO) systems aim at detecting and correcting for optical distortions induced by atmospheric turbulences. The Gemini Multi Conjugated AO System GeMS is operational and regularly used for science observations since 2013 delivering close to diffraction limit resolution over a large field of view. GeMS entered this year into a new era. The laser system has been upgraded from the old 50W Lockheed Martin Coherent Technologies (LMCT) pulsed laser to the Toptica 20/2W CW SodiumStar laser. The laser has been successfully commissioned and is now used regularly in operation. In this paper we first review the performance obtained with the instrument. I will go then into the details of the commissioning of the Toptica laser and show the improvements obtained in term of acquisition, stability, reliability and performance.

Response to major earthquakes affecting Gemini twins

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. 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.