Shane Walker

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.

GeMS: first on-sky results

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.

Science planning for the Gemini 8-m telescopes

The new 8-meter class telescopes represent large investments by the development communities. This means that these telescopes must be operated efficiently to provide the best possible return on these investments and a great deal of effort has been made to provide control software that supports effective use of the telescopes. However, efficient use must be more than just keeping the telescopes operating; it is important that observers be provided tools that enable them work effectively. The Gemini 8 m Telescopes have developed a strategy for helping astronomers plan observations through the design of science programs. While there are a number of unique aspects to this strategy, this paper focuses on the methods used as the foundation for connecting astronomers to the facilities of the observatories during the design of science programs. The methods under development take advantage of emerging Internet technologies to help reduce the maintenance issues normally associated with supporting remote sites, while freeing users from many of the performance problems associated with web-based solutions.

An observation execution system for next-generation large telescopes

The telescope development projects of the 1990s produced a set of capable 8-10m telescopes that are now in operations across the northern and southern hemispheres. This was the first generation of telescopes to benefit from carefully engineered software systems, yet several years of 8m operations have revealed weaknesses in a common architecture employed by many of them. Today engineers are working on the next generation of telescopes, the extremely large telescopes (ELTs), along with their software systems. It is our view that many of the fundamental assumptions about how software systems for 8-m class large telescopes should be constructed are not optimal for the next generation of extremely large telescopes. In fact, these ideas may constrain the solution space and result in overly complex software and increased development costs. This paper points out issues with current architecture solutions and how they impact the software needed for extremely large telescopes. It then provides the outline of a new approach for the design of the software running at the telescope that is targeted towards the development issues of ELTs and large telescope operations.

Experience with a new approach for instrument software at Gemini

Gemini Observatory is using a new approach with instrument software that takes advantage of the strengths of our instrument builders and at the same time better supports our own operational needs. A lightweight software library in conjunction with modern agile software development methodologies is being used to ameliorate the problems encountered with the development of the first and second-generation Gemini instruments. Over the last two years, Gemini and the team constructing the software for the Gemini Planet Imager (GPI) have been using an agile development process to implement the Gemini Instrument Application Interface (GIAPI) and the highlevel control software for the GPI instrument. The GPI is being tested and exercised with the GIAPI, and this has allowed us to perform early end-to-end testing of the instrument software. Early in 2009 for the first time in our development history, we were able to move instrument mechanisms with Gemini software during early instrument construction. As a result of this approach, we discovered and fixed software interface issues between Gemini and GPI. Resolving these problems at this stage is simpler and less expensive than when the full instrument is completed. GPI is currently approaching its integration and testing phase, which will occur in 2010. We expect that utilizing this new approach will yield a more robust software implementation resulting in smoother instrument integration, testing, and commissioning phases. In this paper we describe the key points of our approach and results of applying the new instrument API approach together with agile development methodologies. The paper concludes with lessons learned and suggestions for adapting agile approaches in other astronomy development projects.

Target of Opportunity Observing in Queue Mode at the Gemini North Observatory

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.

Quick response target of opportunity observations at Gemini

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.

The Gemini online data processing system

Processing astronomical images is an inherently resource intensive procedure that is typically time consuming as well. At the same time, first order reductions are particularly important during the observing process since they can provide key quality assessment information. To resolve this conflict, the Online Data Processing (OLDP) system being commissioned at the Gemini Observatory automatically maps reduction sequences onto a cluster of servers during observing, taking advantage of available concurrency where possible. The user constructs a visual representation of the sequence for an observation using the Gemini Observing Tool. No constraints are placed upon the series of steps that comprise the sequence. At runtime, the OLDP reads the reduction sequence from the Observing Database and splits it into smaller pieces for simultaneous execution on the cluster. Recipe steps can be implemented in IRAF, shell scripts, or Java, and other types can be plugged into the architecture without modifying the core of the code base. This paper will introduce the Gemini OLDP and demonstrate how it utilizes modern infrastructure technology like Jini and JavaSpaces to achieve its goals.

Enhancing science program collaboration at Gemini

At Gemini, support for observers during Phase 2 is a collaborative effort among individuals spread across four continents at many institutions. Short Phase 2 preparation periods necessitate close communication between observers and support personnel. Email alone has not been an adequate solution. For the 2003B semester, the Gemini Observing Tool has been extended to allow off-site investigators and national project office support personnel to directly access the science program database. The observer is able to keep up to date with changes by accessing his program at any time. Email notifications are generated automatically when activities occur in the science program lifecycle. This paper will give an overview of how this system, based upon Java and freely available open source software, provides these new capabilities.