The Four Laser Guide Star Facility (4LGSF) is part of the ESO Adaptive Optics Facility, in which one of the VLT telescopes, UT4, is transformed in an adaptive telescope-equipped with a deformable secondary mirror, two adaptive optics systems at the Nasmyth focii and four sodium laser guide star modular units. In this paper we present the design, the assembly and validation test performed so far in Europe on the first laser guide star unit.
The New Adaptive Optics Module for Interferometry (NAOMI)1 is the future low order adaptive optics system to be developed for and installed at the ESO 1.8 m Auxiliary Telescopes (ATs). The four ATs2 are designed for interferometry which they are essentially dedicated for. Currently the AT’s are equipped with a fast, visible tip-tilt sensor called STRAP3 (System for Tip/tilt Removal with Avalanche Photodiodes), and the corrections are applied through a tip-tilt mirror. The goal is to equip all four ATs with a low-order Shack-Hartmann system operating in the visible for the VLTI dual feed light beams in place of the current tip-tilt correction. Because of the limited size of the ATs (1.8m diameter), a low-order system will be sufficient. The goal is to concentrate the energy into a coherent core and to make the encircled energy (into the single mode fibers) stable and less dependent on the atmospheric conditions in order to increase the sensitivity of the interferometric instruments. The system will use the ESO real time computer platform Sparta-light as the baseline. This paper presents the preliminary design concept and outlines the benefits to current and future VLTI instruments.
The ALMA Observatory is currently operating ′Early Science′ observing. The Cycle0 and Cycle1 Calls for Proposals are
part of this Early Science, and in both the ALMA Observing Tool plays a crucial role. This paper describes how the
ALMA OT tackles the problem of making millimeter/sub-millimeter interferometry accessible to the wider community,
while allowing "experts" the power and flexibility they need.
We will also describe our approach to the challenges of supporting multiple customers, and explore the lessons learnt
from the Early Science experiences. Finally we look ahead to the challenges presented by future observing cycles.
Most of the sky is black: picking off the interesting bits is the challenge. By placing pick-off mirrors in the focal plane of
an instrument, it is possible to select light from only the desired sub-fields. The Micro Autonomous Positioning System
(MAPS) is a method for maneuvering pick-off mirrors into position by giving each mirror its own set of wheels. This
paper details the metrology algorithms that are being developed to provide real-time feedback of the robots’ positions.
This will be achieved through imaging high-resolution targets on the robots and analysing the power floor on which they
move. Early tests show that the imaging system is capable of resolving linear motions of lμm and rotation of <1mrad, for
an operating area of 25 x 20 cm.
This paper describes the features and functionality of the UCam (UKATC Universal Camera Control and Data
Acquisition) detector control system with a particular emphasis on development and testing of two 4K×4K CCD camera
systems built recently at UKATC and delivered to a group of telescopes in India. These two camera systems use two
variants of an e2v CCD203 device; a 4k×4k standard back-thinned device and a deep depleted silicon device. Apart from
the expected differences with the spectral response of these devices, other performance differences have been observed
between the two systems such as conversion gain non-linearity, electrical crosstalk between outputs, fringing etc. which
are thought to be related to the silicon thickness. Both these detectors show charge trapping during device power on or
when saturated. The effects of this charge trapping and a solution implemented to minimise it will be presented. The
configuration of the UCAM system, custom built detector mount and fanout board and the overall performance of these
camera systems will also be presented.
This paper describes the software architecture and design concepts used in the UKATC's generic camera control and data
acquisition software system (UCam) which was originally developed for use with the ARC controller hardware. The
ARC detector control electronics are developed by Astronomical Research Cameras (ARC), of San Diego, USA. UCam
provides an alternative software solution programmed in C/C++ and python that runs on a real-time Linux operating
system to achieve critical speed performance for high time resolution instrumentation. UCam is a server based
application that can be accessed remotely and easily integrated as part of a larger instrument control system. It comes
with a user friendly client application interface that has several features including a FITS header editor and support for
interfacing with network devices. Support is also provided for writing automated scripts in python or as text files. UCam
has an application centric design where custom applications for different types of detectors and read out modes can be
developed, downloaded and executed on the ARC controller. The built-in de-multiplexer can be easily reconfigured to
readout any number of channels for almost any type of detector. It also provides support for numerous sampling modes
such as CDS, FOWLER, NDR and threshold limited NDR. UCam has been developed over several years for use on
many instruments such as the Wide Field Infra Red Camera (WFCAM) at UKIRT in Hawaii, the mid-IR
imager/spectrometer UIST and is also used on instruments at SUBARU, Gemini and Palomar.
PyDevCom is a small application written in the python programming language for communicating with astronomical
instrumentation devices (e.g. temperature monitors and controllers, motion controllers, etc.) that
use serial communication interfaces. It provides a highly configurable framework for defining an interface for
communicating with a serial device. The configuration information for PyDevCom is stored in an XML file
which is designed to be easily read and customised. Therefore when an interface to a new device is required,
a new configuration file for the device is all that is needed. This avoids having to write a new device specific
communications application. The core PyDevCom application can be used interactively in a Python terminal, or
may be executed inside a script, providing a great deal of flexibility for testing hardware in the lab. PyDevCom
has its own platform-independent GUI, based on wxPython, which automatically constructs the interface for a
given device from the information in the XML configuration file. Future development for PyDevCom will add
several new user interface features that include a plug-in architecture for adding specially tailored GUI interfaces
written in python. Once these features have been implemented they will extend PyDevCom to function as a
lightweight instrument control system.
Multi-object instruments provide an increasing challenge for pick-off technology (the means by which objects are selected in the focal plane and fed to sub-instruments such as integral field spectrographs). We have developed a technology demonstrator for a new pick-off system. The performance requirements for the demonstrator have been driven by the outline requirements for possible ELT instruments and the science requirements based on an ELT science case. The goals for the pick-off include that the system should capable of positioning upwards of one hundred pick-off mirrors to an accuracy better than 5 microns. Additionally, the system should be able to achieve this for a curved focal surface -- in this instance with a radius of curvature of 2m.
This paper presents the first experimental results from one of the approaches adopted within the Smart Focal Plane project -- that of a Planetary Positioning System. This pick-and place system is so called because it uniquely uses a combination of three rotation stages to place a magnetically mounted pick-off mirror at any position and orientation on the focal surface. A fixed angular offset between the two principal rotation stages ensures that the pick-off mirror is always placed precisely perpendicular to the curved focal plane. The pick-off mirror is gripped and released by a planar micromechanical mechanism which is lowered and raised by a coil-actuated linear stage.
VISTA is a wide-field survey telescope with a 1.6° field of view, sampled with a camera containing a 4 x 4 array of 2K x 2K pixel infrared detectors. The detectors are spaced so an image of the sky can be constructed without gaps by combining 6 overlapping observations, each part of the sky being covered at least twice, except at the tile edges. Unlike a typical ESO-VLT instrument, the camera also has a set of on-board wavefront sensors. The camera has a filter wheel, a collection of pressure and temperature sensors, and a thermal control system for the detectors and the cryostat window, but the most challenging aspect of the camera design is the need to maintain a sustained data rate of 26.8 Mb/second from the infrared detectors. The camera software needs to meet the requirements for VISTA, to fit into the ESO-VLT software architecture, and to interface with an upgraded IRACE system being developed by ESO-VLT. This paper describes the design for the VISTA camera software and discusses the software development process. It describes the solutions we have adopted to achieve the desired data rate, maximise survey speed, meet ESO-VLT standards, interface to the IRACE software and interface the on-board wavefront sensors to the VISTA telescope software.
Ultracam is a high speed, three channel CCD camera designed to provide imaging photometry at high temporal resolution, allowing the study of rapidly changing astronomical phenomena such as eclipses, rapidly flickering light curves and occultation events. It is designed to provide frame rates up to 500 Hz with minimum inter-frame dead time and to time-tag each frame to within 1 millisecond of UT. The high data rates that this instrument produces, together with its use as a visitor instrument at a number of observatories, have lead to a highly modular design. Each major service (camera, control, sequencing, data handlers, etc.) is a separate process that communicates using XML documents via HTTP transport, allowing the services to be redeployed or reconfigured with minimal effort. The use of XML and HTTP also allows a web browser to act as a front end for any of the services, as well as providing easy access to services from other control systems. The overall design allows for simple re-engineering for a variety of imaging systems, and is already expected to provide control of IR arrays for the UKIRT Wide-Field Camera project. The instrument has been successfully commissioned on the William Herschel Telescope.