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Home > Public Information > ING Annual Reports > 1997 > Chapter 2 |
ING Annual Report 1997
Previous: Chapter 1 - Scientific Highlights | Up: Table of Contents | Next: Chapter 3 - Telescope OperationChapter 2
New Instrumentation and Enhancements
WILLIAM HERSCHEL TELESCOPE
Good data continued to be obtained with the prime focus AUTOFIB multi-fibre positioning unit feeding light into the WYFFOS fibre spectrograph. Spectra from thousands of galaxies, hundreds of globular clusters and tens of planetary nebulae in M51 had been gathered in only a few nights on the WHT. However, the operational reliability of the AUTOFIB fibre positioner continued to be problematic. These problems led to a detailed analysis of the faults which resulted in a re-design of the fibre griper mechanism and parts of the fibre support assembly. The new system was put through its paces in December 1997 and was shown to perform very satisfactory. The accuracy of fibre positioning is now good enough to proceed with the manufacturing of a fibre unit with 1.6 arcsec diameter fibres with confidence.
An integral-field spectroscopic facility, INTEGRAL, was deployed at the Nasmyth focus of the WHT. This collaborative development between teams from the Instituto de Astrofísica de Canarias and the Royal Greenwich Observatory picks up and dissects light from extended objects, and channels the light into the WYFFOS fibre spectrograph. Three fibre bundles are available with field sizes ranging from 10 to 40 arcseconds and different fibre core sizes, which allow observers to make the most efficient use of the prevailing seeing conditions. This instrument is particularly useful for kinematic studies of galaxies.
A new UES derotator was commissioned in December 1997. The new derotator has high UV throughput, but a small field of view. The old derotator remains available for long-slit work.
Work progressed on INGRID (the ING Red Imaging Device), the new near-infrared camera for the WHT. Unlike WHIRCAM, this camera will be optimised for a wide field of view at relatively short wavelengths, with good performance expected out to about 2.2 microns. The detector will be a Rockwell 1024 × 1024 HgCdTl array. This camera will be deployed at the Cassegrain focus of the WHT for direct imaging, where it will provide a pixel scale of 0.25 arcseconds/pixel, and it will be the principal detector for the NAOMI Adaptive Optics system, where it will provide a pixel scale of 0.04 arcseconds/pixel. Most of the detailed design of the instrument was finished, and the detector readout electronics were tested using the engineering array in a test camera.
The main instrument development project for the William Herschel Telescope is the NAOMI natural guide star adaptive optics system. A number of milestones were successfully passed. The wavefront sensor and opto-mechanical chassis design phases were completed. The first deployment of the ELECTRA segmented mirror, which will be a key part of NAOMI, suffered some delay, but in June the loop between the (preliminary) Shack-Hartmann wavefront sensor and the 78-element segmented mirror was closed for the first time on a star. This was a key milestone for the project. The next important phase will be to achieve closed loop full strain gauge control over the mirror segments with virtually zero hysteresis, which will allow very accurate wavefront correction.
1 2 3 4 1.- The focal plane end of the standard INTEGRAL fibre bundles. The insert (top left) shows a close up of the bundle with the smallest aperture fibres. [ JPEG | TIFF ]
2.- Back illuminated fibres from the 0.45" bundle. [ JPEG | TIFF ]
3.- INTEGRAL mounted on the GHRIL rotator. The fibre bundles can be seen exiting the instrument on the coupled ring at the back of the instrument. The insert is a close up of the fibre complex, showing plate and also the autoguiding bundles. [ JPEG | TIFF ]
4.- INTEGRAL fibre bundles mounted in a WYFFOS slit unit. [ JPEG | TIFF ]Other instrumentation developments include LIRIS, a cooled near-infrared (0.9-2.5 microns) intermediate-resolution spectrograph for the Cassegrain focus of the WHT. This instrument is being planned by the Instituto de Astrofísica de Canarias. LIRIS will also use a Rockwell 1024 × 1024 HgCdTl array to cover a large spectral range and a wide spatial field of view.
ISAAC NEWTON TELESCOPE
The new prime focus Wide Field Camera was commissioned in May. This system is based on a mosaic of four thinned 2048 × 2048 pixel CCDs. Its scientific performance was unfortunately limited by the relatively poor performance of the CCDs, which led to the decision to look for alternative CCDs to replace the existing set. New and larger thinned detectors were acquired from EEV and the upgrade of the camera was planned to take place early in 1998.
Important progress was made on the initiative to modernise the instrument and telescope control infrastructure. The new infrastructure is based around a DEC-Alpha workstation for the telescope control, and Unix based instrument control and data acquisition systems. This upgrade allowed decommissioning of the very old control computers which became difficult to support and did not comply with the more demanding tasks and much higher data rates.
The upgrades programme has been carried out through various stages, gradually replacing old equipment. This approach caused that observers had to cope with many changes, but on the other hand the telescope did not have to be taken out of service for any substantial length of time.
Towards the end of the year the Cambridge Institute of Astronomy's CIRSI wide field infrared camera was commissioned at the INT as a private instrument. This panoramic wide field camera is based on a mosaic of 4 Rockwell HgCdTl 1024 × 1024 arrays. The absence of cold fore optics limits it use in the thermal infrared, but its collecting area makes it a highly competitive instrument in the near infrared. It will be particularly well-suited for surveys of star-forming regions, low mass stars, distant galaxies, clusters and quasars.
The INT Wide Field Camera (WFC) consists of a 4 chip mosaic assembly. A fifth CCD, a Lesser thinned Loral device, is co-mounted with the science array in the cryostat to provide autoguiding functions (see picture top left) [ JPEG | TIFF ]. The bottom left picture corresponds to the first commissioning on the telescope in May 1997 [ JPEG | TIFF ]. Finally, the picture on the right is a true-colour image of M51 galaxy using BVR imaging on the WFC [ JPEG ]. JACOBUS KAPTEYN TELESCOPE
Parallel to the upgrades of the computing infrastructure on the INT, a similar development took place on the JKT. A Unix based data acquisition system was commissioned in 1997, and full completion of the upgrades programme, which includes a DEC-Alpha based telescope control system and a Unix based instrument control system will take place in 1998.
DETECTOR ENHANCEMENTS
Progress on the contract to procure 2k × 2k pixel thinned Loral CCD continued to be problematic and has not yielded the quality of devices that was aimed for. Also progress on the procurement of thinned 4k × 2k pixel CCD from EEV was slow, but in the fall of 1997 one EEV detector was delivered which did perform satisfactory and quickly became the detector of choice for most observers. The large size of the chip, in combination with the small pixels, the good quantum efficiency, and intrinsically good point spread function, makes this a highly attractive tool for astronomy.
In order to accommodate the strong need for large format thinned devices two 2048 × 2048 pixel thinned devices from SITe were purchased in the beginning of the year and successfully put into operation.
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