William Lupton

First Light Adaptive Optics Images from the Keck II Telescope : A New Era of High Angular Resolution Imagery

ABSTRACT Adaptive optics (AO) is a technology that corrects in real time for the blurring effects of atmospheric turbulence, in principle allowing Earth‐bound telescopes to achieve their diffraction limit and to “see” as clearly as if they were in space. The power of AO using natural guide stars has been amply demonstrated in recent years on telescopes up to 3–4 m in diameter. The next breakthrough in astronomical resolution was expected to occur with the implementation of AO on the new generation of large, 8–10 m diameter telescopes. In this paper we report the initial results from the first of these AO systems, now coming on line on the 10 m diameter Keck II Telescope. The results include the highest angular resolution images ever obtained from a single telescope (0 \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsx...

Performance of the W.M. Keck Observatory Natural Guide Star Adaptive Optic Facility: the first year at the telescope

First light for the Keck II Natural Guide Star (NGS) Adaptive Optics (AO) facility was on the night of February 4, 1999. On the firs attempt at closing the AO loops the image full-width- at-half-maximum (FWHM) went from 0.6 to 0.04 arcsec at H-band (1.65 micrometer wavelength), with a Strehl ratio of 25%. The AO system became an officially scheduled Keck science facility in August 1999; 30 science nights are scheduled in the first half of 2000. The primary purpose of this paper is to present results from this first year at the telescope.

The Keck Interferometer

The Keck Interferometer (KI) combined the two 10 m W. M. Keck Observatory telescopes on Mauna Kea, Hawaii, as a long-baseline near- and mid-infrared interferometer. Funded by NASA, it operated from 2001 until 2012. KI used adaptive optics on the two Keck telescopes to correct the individual wavefronts, as well as active fringe tracking in all modes for path-length control, including the implementation of cophasing to provide long coherent integration times. KI implemented high sensitivity fringe-visibility measurements at H (1.6 μm), K (2.2 μm), and L (3.8 μm) bands, and nulling measurements at N band (10 μm), which were used to address a broad range of science topics. Supporting these capabilities was an extensive interferometer infrastructure and unique instrumentation, including some additional functionality added as part of the NSF-funded ASTRA program. This paper provides an overview of the instrument architecture and some of the key design and implementation decisions, as well as a description of all of the key elements and their configuration at the end of the project. The objective is to provide a view of KI as an integrated system, and to provide adequate technical detail to assess the implementation. Included is a discussion of the operational aspects of the system, as well as of the achieved system performance. Finally, details on V^2 calibration in the presence of detector nonlinearities as applied in the data pipeline are provided.

Experience with EPICS in a wide variety of applications

Currently more than 70 organizations have obtained permission to use EPICS, a set of software packages for building real-time control systems. In this paper representatives from four of these sites discuss the reasons their sites chose EPICS, provide a brief discussion of their control system development, and discuss additional control system tools obtained elsewhere or developed locally.

Initial performance of the Keck AO wavefront controller system

The wavefront controller for the Keck Observatory AO system consists of two separate real-time control loops: a tip-tilt control loop to remove tilt from the incoming wavefront, and a deformable mirror control loop to remove higher-order aberrations. In this paper, we describe these control loops and analyze their performance using diagnostic data acquired during the integration and testing of the AO system on the telescope. Disturbance rejection curves for the controllers are calculated from the experimental data and compared to theory. The residual wavefront errors due to control loop bandwidth are also calculated from the data, and possible improvements to the controller performance are discussed.

Software infrastructure for the Keck II telescope

Many diverse software systems are in use on the Keck I telescope. This is mostly because software standards were low-level (e.g., choice of programming language, computer or operating system) and did not specify use of a particular software environment. Selection of directory structures, messaging systems, tasking environments and support packages was largely left up to individual development groups, although there were some successful instances of group collaborations. For the Keck II telescope, a common set of standards and tools has been agreed on, and the provision and maintenance of these tools is regarded as a group effort. These standards and tools are known as the Keck II Software Infrastructure and include EPICS (Experimental Physics and Industrial Control System), the successful Keck I concept of making all system control available via keyword/value pairs, the Tcl command language, standard logging and error reporting, and common programing standards. This paper discusses some of the successes and failures of the Keck I approach and describes how the Keck II system is evolving from the Keck I system. Some examples of the use of EPICS for telescope control are given, and EPICS as a vehicle for future collaboration is considered.

Pointing and tracking performance of the W.M. Keck Telescope

The achieved pointing and tracking performance of the telescope is presented and compared with the Keck goals. The implications of the current performance on observing are discussed, and planned remedies for deficiencies in pointing and tracking are proposed.

Subsystem coordination on the W. M. Keck telescopes

The Keck Telescope Control System is organized as a set of independent hardware subsystems, a pointing subsystem, and a high-level TCS subsystem. The pointing subsystem handles real-time coordination of telescope, mount, enclosure, rotators and guiders. The TCS subsystem knows which low- level subsystems are required for a given instrument, and manages the parallel initialization, shutdown, status monitoring and fault recovery of the overall system. The TCS subsystem also provides a user interface which presents the system as a table, with an Overall row and a row per subsystem; each row has status and error message fields, and a set of standard controls. This user interface serves as the single point of access to the telescope control system for the observing assistant and the engineer: all the other observing and engineering tools can be launched from it. This paper describes the above paradigm, with special attention being given to the user interface. Potential use of the same model for other applications is discussed.

Keck II Telescope Control System

The experimental physics and industrial control system (EPICS) originated in the high energy physics community and has been used for several years to control accelerators. It is now in use or soon to be in use at several observatories around the world. In 1995, it was decided that Keck II telescope would have a new EPICS-based control system rather than use a copy of the Keck I system. This decision was made because it was felt that EPICS provided a superior software infrastructure to that developed for Keck I, and that it would scale well to encompass adaptive optics and eventual use of the two telescopes for interferometry. The new control system was developed throughout 1995 and the early part of 1996, leading to first light in January 1996, making it the first fully EPICS-controlled telescope control system in the world. This paper describes how EPICS has been used to implement the control system, including a detailed discussion of the axes control, pointing and timing system, and of how they interact with each other.

W.M. Keck Telescope control system

The computing environment and major components of the Keck telescope control system are discussed. This is followed by a discussion of calibration procedures and a review of current status and problems.