 | |||
|
| Home > Public Information > ING Annual Reports > 1995 > New Instrumentaion and Enhancements |
|
| |||
|
| Home > Public Information > ING Annual Reports > 1995 > New Instrumentaion and Enhancements |
ING Annual Report 1995/96
Previous: Chapter 1 - Scientific Highlights | Up: Table of Contents | Next: Chapter 3 - Telescope PerfomanceChapter 2
New Instrumentation and Enhancements
WILLIAM HERSCHEL TELESCOPEThe capability of instruments offered to observers at ING was augmented in 1995 through the commissioning of the WHIRCAM infrared imaging camera, based on a 256 x 256 element InSb array. It was subsequently used for many observing runs. WHIRCAM also served as the science detector for the Durham prototype adaptive-optics system MARTINI. To provide optimal throughput in the infrared a new derotator was commissioned for the Nasmyth focus. First steps were taken for subsequent commissioning of WHIRCAM in the cassegrain focus, where the instrument was anticipated to be mounted permanently on the standard acquisition and guiding unit. Unfortunately, in December 1996 the detector failed and had to be sent back to the manufacturer for repair.
The MARTINI-3 adaptive-optics system was successfully commissioned in co-phased mode, which achieved images with 0.2-arcsec FWHM over the full 13-arcsec field of view. These encouraging results demonstrated the successful application of adaptive-optics techniques to relatively faint targets, including extra-galactic objects. These trials also provided essential input for the development of the common-user NAOMI adaptive-optics system, which is a key element of ING's development programme.The wide field available at the prime focus of WHT is very effectively exploited through the development of the prime focus fiber positioning unit, AUTOFIB, feeding the intermediate resolution fiber spectrograph, WYFFOS. This system is capable of measuring up to 120 objects over a field of 40 arcminutes wide. The individual fibers are positioned automatically in the focal plane by a robotic gripper unit working to an overall accuracy of better than 10 microns. Light captured by the fibers is run along the telescope structure to the Nasmyth platform and then fed into the WYFFOS spectrograph. This spectrograph has different modes of operation, yielding resolutions ranging from 1 to 10 Å.
The commissioning of this complex fiber system was carried out in various stages during 1995 and 1996. A number of problems, both with the AUTOFIB positioning unit and with the WYFFOS spectrograph plagued the commissioning. Some fundamental problems with the robotic fiber positioning unit persisted and required a major redesign. In spite of these difficulties, the system was used successfully for various observing runs and produced spectra of many hundreds of galaxies and stellar objects.
Another instrument specifically exploiting the wide field of the WHT prime focus was the mosaic CCD camera (totaling 5000 x 8000 pixels) built at NAO Japan, which was first deployed on the WHT in 1996. The (unfilled) mosaic CCD covers 30' x 50' in four exposures, i.e. most of the prime-focus field, and provides a superb complement to the AUTOFIB/WYFFOS fibre-fed spectrograph. This instrument, a prototype for the Subaru telescope, is a visiting instrument at ING.
The ISIS intermediate resolution spectrograph in the cassegrain focus of the WHT saw an upgrade of its polarisation unit in 1996. Although the optical capabilities remained the same, the operational accuracy was substantially improved and made more reliable.
INTEGRAL, the integral field fiber feed for the WYFFOS spectrograph, was being built by a collaborative team from the IAC, RGO, and ING. Design and manufacture progressed well. This instrument will be deployed at the nasmyth focus of the WHT with a variety of integral field fiber bundels for optimized sampling, depending on the science requirements and the seeing conditions.
Observations of the globular cluster M15 using the MARTINI adaptive-optics system on the WHT. Shown on the left is the K-band uncorrected image [GIF] and on the right the corrected image. [GIF]
ISAAC NEWTON TELESCOPEThe prime-focus Wide Field Camera approached completion in 1996. The camera contains a mosaic of four 2048 x 2048 pixel thinned Loral CCDs. The delivery of these devices was substantially delayed which resulted in much later commissioning of the instrument than originally anticipated. The camera started to be used for scheduled common-user observations in 1996.
MUSICOS, a fibre fed echelle spectrograph, constructed by an ESA/Leiden group, was successfully commissioned for use on the INT in 1996. Much useful science was obtained from the scheduled programmes. MUSICOS was located in the old photographic developing room on the INT observing floor. This instrument fills a niche for high resolution spectroscopy (R ~ 40,000) for objects of intermediate brightness during bright time. The possibility of retaining this instrument on a long-term basis was under investigation.
DETECTOR ENHANCEMENTS
A large-format unthinned 2220x1280 EEV CCD was commissioned for use with UES in 1995. In 1996 a 2048 x 2048 thinned Loral CCD was commissioned as a general-purpose detector for the WHT. This device had an excellent UV and blue response, but suffered from cosmetic defects and operational complexities. Furthermore, the relatively poor point-spread function and relatively high read noise limited the use of this detector. The 1024 x 1024 thinned TEK devices remained the work horse detectors at ING.
The IPCS detector was used for the last time in February 1996. Its chief advantage over CCDs was its zero readout noise which gave it an advantage for very faint sources and high-resolution spectroscopy. But since CCDs became available with very low readout noise, combined with their high quantum efficiency, these detector reduced the advantage of the IPCS detector, which was subsequently decommissioned.
A fast and continuous readout mode was developed for detectors on the WHT. This new mode of operation allows very short exposure times, as short as 0.2 seconds, with similar low dead times. This readout mode is particularly suited for high-speed spectroscopy of rapidly varying sources such as X-ray binaries and flare stars. This readout mode was achieved by only adapting the CCD controller software and the high-level data acquisition software.
Previous: Chapter 1 - Scientific Highlights | Up: Table of Contents | Next: Chapter 3 - Telescope Perfomance© Isaac Newton Group of Telescopes
