Steven L. Allen

Representations of Spectral Coordinates in FITS

Greisen & Calabretta (2002) describe a generalized method for specifying the coordinates of FITS data samples. Following that general method, Calabretta & Greisen (2002) describe detailed conventions for dening celestial coordinates as they are projected onto a two-dimensional plane. The present paper extends the discussion to the spectral coordinates of wavelength, frequency, and velocity. World coordinate functions are dened for spectral axes sampled linearly in wavelength, frequency, or velocity, linearly in the logarithm of wavelength or frequency, as projected by ideal dispersing elements, and as specied by a lookup table.

The low-resolution imaging spectrograph red channel CCD upgrade: fully depleted, high-resistivity CCDs for Keck

A mosaic of two 2k x 4k fully depleted, high resistivity CCD detectors was installed in the red channel of the Low Resolution Imaging Spectrograph for the Keck-I Telescope in June, 2009 replacing a monolithic Tektronix/SITe 2k x 2k CCD. These CCDs were fabricated at Lawrence Berkeley National Laboratory (LBNL) and packaged and characterized by UCO/Lick Observatory. Major goals of the detector upgrade were increased throughput and reduced interference fringing at wavelengths beyond 800 nm, as well as improvements in the maintainability and serviceability of the instrument. We report on the main features of the design, the results of optimizing detector performance during integration and testing, as well as the throughput, sensitivity and performance of the instrument as characterized during commissioning.

Representations of time coordinates in FITS - Time and relative dimension in space

Context. In a series of three previous papers, formulation and specifics of the representation of world coordinate transformations in FITS data have been presented. This fourth paper deals with encoding time. Aims. Time on all scales and precisions known in astronomical datasets is to be described in an unambiguous, complete, and selfconsistent manner. Methods. Employing the well-established World Coordinate System (WCS) framework, and maintaining compatibility with the FITS conventions that are currently in use to specify time, the standard is extended to describe rigorously the time coordinate. Results. World coordinate functions are defined for temporal axes sampled linearly and as specified by a lookup table. The resulting standard is consistent with the existing FITS WCS standards and specifies a metadata set that achieves the aims enunciated above.

Optimizing interactive performance for long-distance remote observing

Remote observing is the dominant mode of operation for both Keck Telescopes and their associated instruments. Over 90% of all Keck observations are carried out remotely from the Keck Headquarters in Waimea, Hawaii (located 40 kilometers from the telescopes on the summit of Mauna Kea), and this year represents the tenth anniversary of the start of Keck remote observing from Waimea. In addition, an increasing number of observations are now conducted by geographically-dispersed observing teams, with some team members working from Waimea while others collaborate from Keck remote observing facilities located in California. Such facilities are now operational on four campuses of the University of California and at the California Institute of Technology. Details of the motivation and planning for those facilities and the software architecture on which they were originally based are discussed in several previous reports. The most recent of those papers reported the results of various measurements of interactive performance as a function of alternative networking protocols (e.g., ssh, X, VNC) and software topologies. This report updates those results to reflect performance improvements that have occurred over the past two years as a result of upgrades to hardware, software, and network configurations at the respective sites. It also explores how the Keck remote observing effort has evolved over the past decade in response to the increased number and diversity of Keck instruments and the growing number of mainland remote observing sites.

Methods for measuring and reducing slippage of friction rollers employed in off-axis couplings of position encoders to telescopes

Instrumentation and procedures developed for the study of friction-roller slippage in off-axis couplings of telescope position encoders are presented, and the designs of rollers and their mountings are examined with a view to the characterization of adjustment techniques yielding optimal alignment of the rollers to minimize slippage. Attention is given to the use of various types of fiducials, including GEO satellites and inexpensive optoelectronic sensors, to gather measures of both telescope-position encoder repeatability and telescope hysteresis which are independent of the telescope-pointing model.

The DEIMOS flexure compensation system: overview and operational results

The DEep Imaging Multi-Object Spectrograph (DEIMOS) was commissioned on Keck II in June 2002. It employs a closed-loop flexure compensation system (FCS) to measure and compensate for image motion resulting from gravitationally-induced flexure of spectrograph elements. The FCS utilizes a set of fiber-fed FCS light sources located at the edges of the instrument focal plane to produce a corresponding set of spots on a pair of FCS CCD detectors located on either side of the science CCD mosaic. (This FCS light follows the same light path through the instrument as the science spectra.) During science exposures, the FCS detectors are read out several times per minute. These FCS images are analyzed in real time to measure any translational motion of the FCS spots and to derive correction signals; those signals drive active optical mechanisms which steer the spots back to their nominal positions, thus stabilizing the images on the FCS CCDs and the science mosaic. This paper describes the commissioning of the DEIMOS FCS system, its continued evolution during its first 18 months of operation on the telescope, and its operational performance over that period. We describe the various challenges encountered while refining the initial FCS prototype (deployed at commissioning) into a fully-operational and highly-reliable system that is now an essential component of the instrument. These challenges include: reducing stray light from FCS light sources to an acceptable level; resolving interactions between FCS acquisition and slit mask alignment; providing robust rejection of cosmic ray events in FCS images; implementing a graphical user interface for FCS control and status.

Another look at web-enabled instrument monitoring and control

Web-enabled user interfaces for the control and monitoring of instruments and telescopes have a checkered history. However, the remarkable interactive speed and quality of Google Maps and Google Suggests have led us, like others, to take another look at implementing services over the Web. The so-called AJAX mechanism enables simple, lightweight, efficient, and responsive interfaces in nearly any modern Web browser. We discuss methods, security, and other implementation issues for sample interfaces that include telescope monitoring, instrument control, and weather station information.

A shared approach to supporting remote observing for multiple observatories

The University of California (UC) began operating the Lick Observatory onMount Hamilton, California in 1888. Nearly a century later, UC became a founding partner in the establishment of theW. M. Keck Observatory (WMKO) in Hawaii, and it is now a founding partner in the Thirty Meter Telescope (TMT) project. Currently, most UC-affiliated observers conduct the majority of their ground-based observations using either the Keck 10-meter Telescopes on Mauna Kea or one or more of the six Lick telescopes now in operation on Mount Hamilton; some use both the Keck and Lick Telescopes. Within the next decade, these observers should also have the option of observing with the TMT if construction proceeds on schedule. During the current decade, a growing fraction of the observations on both the Keck and Lick Telescopes have been conducted from remote observing facilities located at the observers home institution; we anticipate that TMT observers will expect the same. Such facilities are now operational at 8 of the 10 campuses of UC and at the UC-operated Lawrence Berkeley National Laboratory (LBNL); similar facilities are also operational at several other Keck-affiliated institutions. All of the UC-operated remote observing facilities are currently dual-use, supporting remote observations with either the Keck or Lick Telescopes. We report on our first three years of operating such dual-use facilities and describe the similarities and differences between the Keck and Lick remote observing procedures. We also examine scheduling issues and explore the possibility of extending these facilities to support TMT observations.

Realizing software longevity over a system's lifetime

A successful instrument or telescope will measure its productive lifetime in decades; over that period, the technology behind the control hardware and software will evolve, and be replaced on a per-component basis. These new components must successfully integrate with the old, and the difficulty of that integration depends strongly on the design decisions made over the course of the facilitys history. The same decisions impact the ultimate success of each upgrade, as measured in terms of observing efficiency and maintenance cost. We offer a case study of these critical design decisions, analyzing the layers of software deployed for instruments under the care of UCO/Lick Observatory, including recent upgrades to the Low Resolution Imaging Spectrometer (LRIS) at Keck Observatory in Hawaii, as well as the Kast spectrograph, Lick Adaptive Optics system, and Hamilton spectrograph, all at Lick Observatorys Shane 3-meter Telescope at Mt. Hamilton. These issues play directly into design considerations for the software intended for use at the next generation of telescopes, such as the Thirty Meter Telescope. We conduct our analysis with the future of observational astronomy infrastructure firmly in mind.

DIVISION XII / COMMISSON 5 / WORKING GROUP: FITS

The business meeting began with a brief review of the current rules and procedures of the WG, which are documented on the WG web page. Four regional FITS committees have been established by the WG, covering North American, Europe, Japan, and Australian/New Zealand, to provide advice to the WG on pending proposals. While it is recognized that this committee structure might need to be revised to provide representation to other regions, the current system is working well, and there were no motions to make any changes at this time.