The new Keck Observatory Telescope Control System is now deployed for regular operations on Keck 2 and the deployment on both telescopes, Keck 1 and Keck 2, is expected to be completed by the time this paper is published. Two new instruments, KCWI and NIRES, were commissioned with the new control system on Keck 2. The upgrade project was a major undertaking replacing the original software architecture and modules, as well as many obsolete hardware components. During the long testing phase, we discovered deficiencies, which we corrected with modifications of the original design. This paper gives a summary of the achieved performance, the issues involving deploying a new system while remaining in full operation, and lessons learned in design and implementation of such a large system.
Launched in 2009, Keck Observatory’s Telescope Control System Upgrade (TCSU) project set out to improve Keck’s telescope pointing, tracking, and offsetting performance as well as increase maintainability and reliability. The project went online full time on the Keck 2 telescope in October 2017 and on the Keck 1 telescope in March 2018 after a notable delay due to a re-design of the azimuth and elevation encoder mounting systems. This paper discusses the details and challenges of implementing this large and complicated system while never requiring a shutdown of either telescope. The TCSU project replaced all of the major elements of the telescope controls, rotator and secondary mirror controls, and safety system. National Instrument’s reconfigurable I/O technology (i.e. NI RIO), with their embedded field programmable gate arrays (FPGAs), are used as the core of the telescope’s digital velocity control loop, structural filter, and tachometer filter. They were also used to create a monitoring and safety system for the rotator velocity controller as well as reading the newly installed tilt meters used to greatly improve pointing performance. Delta Tau’s family of “Brick” programmable multi-axis controllers, i.e. PMAC or BRICK, are used to control the rotator and secondary mirror. They enable better tuning and faster slew speeds for these subsystems. An Allen Bradley’s ControlLogix® controller and the family of FLEX™ Input/Output (IO) modules were used to create a distributed safety system able to handle a wide variety of signal types. This technology refresh based on commercial off the shelf equipment replaced much of our obsolete and custom equipment. A significant part of the project was the installation of new telescope azimuth and elevation position encoders based on Heidenhain’s 40 micron grading tape scales. Interpolated to a 10 nanometer resolution, the new encoders provide true 4 mas resolution in azimuth and 1 mas resolution in elevation. This is a big improvement to Keck’s position sensing when compared to the old rotary incremental encoders. The installation required a significant amount of mechanical infrastructure to house them. Additionally, two tilt meters were installed to sense the telescope’s varying vertical angle as a function of azimuth, mainly due to the azimuth bearing’s axial runout. The encoders and tilt meters are the primary reason for achieving the greatly improved pointing and tracking performance . Finally, a switching solution using solid state relays and dual network switches was installed to provide seamless and rapid switching between the old and new control systems during commissioning. Although this component is a simple design and does not boast of any new technology, it is one of the key components that enabled the successful testing of the new equipment while keeping the old system operational as a backup for night time observing as well as for baseline performance comparisons. It allowed us to switch a variety of signal types and was very cost effective when compared to available products.
Since the start of operations in 1993, the twin 10 meter W. M. Keck Observatory telescopes have continued to maximize their scientific impact and to produce transformative discoveries that keep the observing community on the frontiers of astronomical research. Upgraded capabilities and new instrumentation are provided though collaborative partnerships with Caltech and UC instrument development teams. The observatory adapts and responds to the observers’ evolving needs as defined in the observatory’s strategic plan, periodically refreshed in collaboration with the science community. This paper summarizes the performance of recently commissioned infrastructure projects, technology upgrades, and new additions to the suite of instrumentation at the observatory. We will also provide a status of projects currently in the design or development phase, and since we need to keep our eye on the future, we mention projects in exploratory phases that originate from our strategic plan. Recently commissioned projects include telescope control system upgrades, OSIRIS spectrometer and imager upgrades, and deployments of the Keck Cosmic Web Imager (KCWI), the Near-Infrared Echellette Spectrometer (NIRES), and the Keck I Deployable Tertiary Mirror (KIDM3). Under development are upgrades to the NIRSPEC instrument and adaptive optics (AO) system. Major instrumentation in design phases include the Keck Cosmic Reionization Mapper and the Keck Planet Finder. Future instrumentation studies and proposals underway include a Ground Layer Adaptive Optics system, NIRC2 upgrades, the energy sensitive instrument KRAKENS, an integral field spectrograph LIGER, and a laser tomography AO upgrade. Last, we briefly discuss recovering MOSFIRE and its return to science operations.
Pointing and tracking performance is one of the key metrics that characterize a telescope's overall efficiency. The pointing performance of the Keck telescopes, which use rotary friction encoders to provide position feedback to the control system, has been surpassed by newer large telescopes with more precise encoder systems. While poor tracking can be compensated with guiding, poor blind pointing performance can lead to loss of observing time. In this paper we present a history of the efforts to reduce the impact of poor pointing, as well as the improvements achieved after the installation of new tape encoders. We will discuss the calibration and testing methods and the tools for monitoring and maintaining the desired pointing performance. A comparative analysis of the pointing performance before and after the telescope control system upgrade will also be presented.
The Keck I and II telescopes have been operational respectively since 1990 and 1996. Operational improvements are
sought to decrease the settling time in response to short moves. The structural response of the open loop system has been
re-identified and the mount control design has been re-examined. Changes to the mount control compensators and
command shaping architecture have been proposed in order to achieve improved response. Results from these studies are
presented, both theoretical and experimental.
Natural Guide Star (NGS) and Laser Guide Star (LGS) Adaptive Optics (AO) have been offered for routine science
operations to the W. M. Keck Observatory community since 2000 and late 2004, respectively. The AO operations team
is now supporting ~100 nights of AO observing with four different instruments, including over fifty nights of LGS AO
per semester. In this paper we describe improvements to AO operations to handle the large number of nights and to
accommodate the recent upgrade to the wavefront sensor and wavefront controller. We report on the observing
efficiency, image quality, scientific productivity, impact analysis from satellite safety procedures and discuss the support
load required to operate AO at Keck. We conclude the paper by presenting our plans for dual LGS AO operations with
Keck I - Keck II LGS, starting in 2009.