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| Home > Public Information > ING Annual Reports > 1995 > Telescope Operation |
ING Annual Report 1995/96
Previous: Chapter 3 - Telescope Perfomance | Up: Table of Contents | Next: Chapter 5 Organisation and StaffChapter 4
Telescope Operation
TELESCOPE OPERATIONSIn 1995 a new technique for cleaning the primary mirror optics was tested, using CO2 snow which is gently sprayed over the mirror surface, carrying the dust particles with it. Since 1996, besides the annual re-aluminising, the primary mirrors of the three telescopes were cleaned once every two months in-situ using CO2 snow. The results looked promising, with much reduced dust buildup throughout the year. From visual inspection and measurements of the mirror reflectivity it is anticipated that with regular in-situ mirror cleaning snow the periods between aluminising can be extended to two years or more.
The control rooms of each of the telescopes were substantial modified. In particular a new control desk was installed for the WHT. This desk is much more spacious, provides a better work environment, and improved protection for the electronics and cabling. Furthermore, partitioning walls within the control room now provide a better layed out and more quiet general computing area. The control rooms of the INT and JKT underwent similar face lifts to keep pace with the upgraded equipment and changing work requirements.
A key area of attention at ING was the evaluation of seeing quality. The assessment of seeing at the focus of the WHT, and a comparison with the undisturbed site seeing outside the telescope building provides fundamental input to the design of adaptive-optics systems, and serves the general aim of improving the image quality of the telescope. Two new diagnostic tool were installed and taken into operation in 1995: the Differential Image Motion Monitor (DIMM) which was installed on its own observing tower, some 50 meters away from the WHT building, and a Shack-Hartmann fast optical wavefront sensor (JOSE), which was operated from the Nasmyth focus on the WHT. Both diagnostic tools were used on a regular basis throughout the years, through half-hour overrides of the scheduled observations. Visiting scientists were very cooperative and understood the need for these disruptions of their observations. Good sampling throughout the various seasons and different parts of the night were obtained. Besides these regular measurements also targeted site characterization campaigns took place. Once a large database of observations has been obtained, it will become clear how the quality of La Palma as an observing site compares to other sites, and how the dome and telescope structure affect seeing quality.
Left: The tower with the DIMM on the top at a height of 5 m above ground. The DIMM is based on a 20 cm Celestron telescope. The WHT in the background is 50 m away and about 15 m above the level of the DIMM. [JPEG|TIFF]
Substantial progress was made on remedial work to reduce heat input into the dome environment with the aim to achieve improved seeing conditions. A new services building, external to, and downwind from the WHT was completed. An improved oil cooling system for the WHT hydrostatic bearings was installed in this building. The new oil cooling plant keeps the oil at a pre-set level corresponding roughly to the night-time air temperature. Eventually also the cooling plant required for instrument and mirror cooling will be installed here.
Towards the end of 1995 the original airbag mirror-support system on the INT was replaced by a bellowphragm three-sector mirror support system similar to that of the WHT. This new system has proven to be much more robust in operation.
In 1996 major advances were made on the re-engineering programme on the INT. Through intermediate steps, gradually fasing out obsolete computers and electronics, the new data acquisition system was installed. These improvements dramatically reduced the CCD readout overheads and allowed observers to immediately access their data on a workstation. A similar upgrade took place on the JKT.
Optical tests of the JKT primary mirror and its support were undertaken in 1995. These tests indicated that the mirror support system is inadequate and limits the best achievable image quality. Telescope pointing and image quality would benefit from an improved mirror support system. An upgrade to the support system is being considered.
In recognition of the potential dangers of working alone, in an isolated environment, the JKT was fitted out with a lone worker alarm system which automatically alerts other workers on-site, should the individual become motionless, or press the manual alarm on the unit.
Following a continuing decline in the use of the Peoples Photometer on the JKT, this instrument was decommissioned in 1996.
OBSERVATORY INFRASTRUCTURE
The temporary office accommodation outside the main WHT telescope building, known as the Casa Blanca, was demolished. To compensate the associated loss of office space, additional offices were constructed in the INT building. However, it became clear that only a sea-level base could adequately meet the long-term accommodation requirements.
In 1996 the Mayantigo building in Santa Cruz was identified as the most suitable location to establish a sea-level base. Agreement was reached with the Galileo telescope and with the Nordic Optical Telescope to collaborate with ING to establish a joint astronomy centre in Santa Cruz de La Palma. Offices were planned and constructed, library, communications and computing infrastructure was installed, and staff commenced to occupy their new offices during the fall of 1996. These new facilities at sea level substantially reduced the need to travel up to site for many staff.
Right: The sea-level office in Santa Cruz de La Palma (green building) came into use during 1996. [JPEG]
Previous: Chapter 3 - Telescope Perfomance | Up: Table of Contents | Next: Chapter 5 Organisation and Staff© Isaac Newton Group of Telescopes
