The sky coverage and performance of laser guide star (LGS) adaptive optics (AO) systems is limited by the natural guide star (NGS) used for low order correction. This limitation can be dramatically reduced by measuring the tip and tilt of the NGS in the near-infrared where the NGS is partially corrected by the LGS AO system and where stars are generally several magnitudes brighter than at visible wavelengths. We present the design of a near-infrared tip-tilt sensor that has recently been integrated with the Keck I telescope’s LGS AO system along with some initial on-sky results. The implementation involved modifications to the AO bench, real-time control system, and higher level controls and operations software that will also be discussed. The tip-tilt sensor is a H2RG-based near-infrared camera with 0.05 arc second pixels. Low noise at high sample rates is achieved by only reading a small region of interest, from 2×2 to 16×16 pixels, centered on an NGS anywhere in the 100 arc second diameter field. The sensor operates at either Ks or H-band using light reflected by a choice of dichroic beamsplitters located in front of the OSIRIS integral field spectrograph.
The W. M. Keck Observatory recently completed an upgrade to the Shutter Drive System on the Keck 1 dome. Due to three major failures on the shutters we decided to undertake a multimillion dollar, multiyear effort to upgrade the drive system. The intention was to increase the system safety factors, to prevent potential problems, to improve maintenance of the system, and to add the capability of the shutter being used as a tracking windscreen, reducing wind effects on the telescope, thereby improving observing. Our solution included the replacement of the drive system with a new drive train and control mechanism, as well as various modifications to existing infrastructure. We'll describe the project from inception to conclusion, and illustrate various approaches helpful to managing this large project while minimizing observatory downtime. We'll discuss control schemes, safety features, failure mode investigations and some heat dissipation concerns. We'll also describe work scheduling, and some prototyping options helpful to ensure success of the project. Finally we'll present some lessons learned from retrofitting a large, essential system of an operating telescope.
The W. M. Keck Observatory is in the process of formalizing its engineering process across the observatory. Over the years we have developed separate systems in separate departments; we are now creating a unified workflow and documentation system. We'll discuss the context, and propose a process for implementation. We'll describe resources, functions, and tools required for effective development and maintenance of any engineering process. The astronomy community is different from a typical manufacturing environment, and implications for off-the-shelf solutions as well as custom developments will be presented in the context of being an appropriate solution to our type of organization.
Specific focus will be placed on the role of documentation as part of this process. We'll discuss different types of documentation and implications for long-term maintenance. We'll describe collaboration tools for both internal and external development and maintenance. We'll discuss paper documentation and current parametric CAD models, and how to maintain those for the life of the observatory. We'll present tools for fast search and retrieval of this information. Finally we'll present lessons learned that may be applied to any such a process.
The W.M. Keck Observatory is conducting a focused effort to identify and mitigate facility vibrations that significantly affect optimal optical performance. This effort should improve the performance of both Keck adaptive optics systems, the laser guide star, the AO instruments, and the interferometer, and will benefit future high precision instruments.
We present our strategy for mitigating vibrations in a large ground-based telescope. Our approach is to establish reasonable confidence in identifying the facility vibration sources that most significantly deteriorate optical performance. For the interferometer we completed vibration surveys that correlate vibrations on the interferometer beam path with direct vibration measurements on the telescope structure and facility. We developed a metric to evaluate the effect of vibrations on the entire interferometer beamline. From our surveys, we prioritized facility components to be addressed, and developed approaches to mitigate key vibrations contributions. Initial results show large local improvements, and global improvements to our vibration environment.