Day-to-day telescope operations activities are carried out by a single Operation
Team covering the three telescopes. Efforts of day-time and night-time support
activities focus on the WHT. On this telescope six main common-user instruments
are offered, and many observing teams pass the scene. The INT on the other
hand operates in a much simpler fashion and is essentially a two-instrument
facility, while the JKT only supports one instrument. For the night time operation
a telescope operator is present each night on the WHT and some of the nights
on the INT. At the JKT no night time operator support is available to visiting
observers. Astronomy support is offered to all visiting astronomers on the
first night of their observing run, and at night engineering support is always
around. Modernisation and integration of the various control systems have
resulted that the INT and JKT can now easily be operated by a single person.
On the JKT astronomy support is largely carried out by students.
Care of ING’s prime optical components, the telescope mirrors, remains an
important recurrent aspect of the day-to-day work at the observatory. We continued
to CO2 snow-clean the WHT primary mirror. However, in line with
findings at other observatories, tests have shown that regular mirror washing
in combination with snow cleaning helps keep reflectivity high, reduces scatter
of light, and relaxes the need for regular re-aluminising. During the year
the first experiments with mirror washing were carried out with good results.
In situ mirror washing offers a significant engineering challenge in order
to protect the telescope and ancillary equipment against water.
The implementation programme of the new San Diego controllers (SDSU-2) and
control software and hardware to replace the older generation of controllers
has progressed well. The new system was taken in use with all science detectors
available on the INT and with nearly all detectors at the WHT. It provides
much faster readout of CCDs and significantly improves observing efficiency.
The same system has now also been implemented for operation with the IR Hawaii
array in the new infrared camera on the WHT, INGRID.
The CCDs currently available at ING have overall excellent characteristics,
but one weakness in the suite of CCDs offered to astronomers is the relatively
low quantum efficiency beyond 800nm and interference fringes between the front
surface and the back plane of the detector, hampering accurate flat field
calibration. To resolve this weakness ING has joined a consortium effort for
the development of a new generation of MIT/Lincoln laboratory CCDs with nearly
twice the quantum efficiency at far red wavelengths and very little fringing.
The first of the science grade devices are expected for delivery in 2002.
In previous years ING’s Differential Image Motion Monitor (DIMM) had provided
valuable information on the site seeing conditions. The operational overheads
in operating the DIMM have meant that this system could only be operated on
a campaign basis. In view of the adaptive optics observations, in particular
when carried out in queue scheduled mode, the need for continuous information
on the actual seeing condition becomes essential. But also for other types
of observations it has been found useful to have an accurate measure of the
free atmosphere seeing. For this reason the ROBODIMM project was initiated
to provide continuous seeing measurements using a system that can operate
in an unassisted, robotic fashion. ROBODIMM will become operational in 2002.
Over the two reporting years the legacy computer network infrastructure
was successfully replaced with a 100 megabit per second network using structured
cabling. Due to the complexity of the computer infrastructure and the requirement
not to interrupt telescope operation this took more than a year to complete.
This network enhancement not only provides an increase in network capacity
of an order of magnitude, but it also provides a backbone upon which further
increases in network capacity may be realised. This new network has brought
many advantages to the ING in terms of network management and security, and
these improvements have also been appreciated by visiting astronomers.
In line with the network enhancements, data archiving and storage within
the ING has witnessed a number of disparate but crucial changes such as the
successful testing of a system to automatically create “D” tapes, the introduction
of an elaborate backup system, which was developed in-house, and the inauguration
of two new RAID systems. These projects are complemented by the introduction
of a Pioneer library system capable of writing to and reading from CDs and
DVDs. These towers each have the capability of housing 6.8Tb of double-sided
medium allowing data to remain on-line for ten times longer than was previously
possible. This is not only advantageous for visiting observers, but also reduces
much of the day-to-day pressure to manage and guarantee a secure data flow
as raw data from the ING telescopes is now automatically recorded on DVD-R
disks for eventual transfer to the ING archive at Cambridge. With these enhancements
in place ING can keep abreast with the ever growing quantity of data generated
by our observing systems.
On the INT the wide field camera is used much of the time for carrying out
a wide field survey of the sky. This survey project prompted the initiation
of a project to vastly improve the data processing capability for pipeline
data reduction. This so-called Beowulf system is based upon a specialised
parallel processing Linux-PC cluster running the pipeline data processing
software developed at the Cambridge Astronomy Survey Unit in the UK. The introduction
of a Beowulf system complemented ING’s data handling strategy and in particular
consolidated the above mentioned new computer network with the new CD/DVD
systems. The pipeline offers fully automatic quick-look reduction for immediate
quality assessment at the telescope, and a science pipeline offers a reduced
data product shortly after the end of the observing run. Observers can submit
their observations to the pipeline at the end of the night and allow them
to view fully processed data —including object catalogues— the following
afternoon. The science pipeline requires only a small amount of human intervention
in order to ensure use of the best possible calibration frames.
The consumption of liquid nitrogen has gradually increased over the years
and is expected to increase further in the future as more detectors and instruments
come on line. The production capacity of the existing plant had become insufficient
to meet future demands, as the plant supplies not only the ING telescopes
but also other telescopes at the observatory. To resolve this problem, jointly
with the Galileo Telescope and Nordic Optical Telescope groups a second liquid
nitrogen production unit was purchased and installed. The new plant together
with the old unit and enhanced storage capacity will be able to meet current
and future demand.
An initiative has been started to implement a number of low-cost house-keeping
measures in the INT building with the aim to reduce locally induced seeing
and hence improve image quality. Experiments with the Differential Image Motion
Monitor in previous years provided firm quantitative evidence for the popular
belief that seeing at the INT is worse than the quality of the sky would
allow. On the basis of this it was decided to implement a number of simple
measures to reduce the heat input into the dome, such as ventilation of cold
air into the building below the observing floor.
The ageing Westinghouse acquisition TV system on the WHT was replaced by
a modern commercial CCD-based TV system. The new system, although somewhat
limited in capability, provides much improved image quality and allows acquisition
of much fainter objects.
During the summer of 2000 both the WHT and INT domes were painted externally.
This major maintenance work was managed so not to affect the observing programme
in any way.
Figure 1. A view of the ING liquid nitrogen plant
with the new production unit in the foreground. [ JPEG
| TIFF ]
The WHT supports a versatile set of common-user instruments, ranging from
optical and IR imagers, to medium and high resolution spectrographs. But apart
from the facility-class instruments, as in previous years the WHT has remained
popular with visiting instruments. Most notable visitors have been the ESA/ESTEC’s
super conducting-tunnel-junction camera S-Cam, the SAURON integral field
spectrograph, and the Planetary Nebula Spectrograph.
Figure 2. Instrument capability of the William
Herschel Telescope. [ JPEG | TIFF ]
Of these visiting instrument, the ESA/ESTEC’s innovative super conducting-tunnel-junction
camera S-Cam was probably the most technologically exciting. The unique technology
deployed in this camera permits measurement of both the energy and time of
arrival of each photon striking the detector array at very high detection
efficiency. During three observing runs technical commissioning was combined
with science observations. The detector deployed in S-Cam had only 6 by 6
pixels, but it is expected that in the near future S-Cam will feature a larger
format detector with better wavelength resolution.
The SAURON integral field spectrograph had several visits to the WHT. This
instrument is a collaborative project between research groups in Leiden, Lyon
and Durham. The instrument uses a lenslet array to dissect the telescope focal
plane in many apertures, and in one exposure a spectrum for each aperture
is obtained. A huge multiplexing advantage is thus obtained, which makes this
spectrograph highly suitable for measuring the kinematics of nearby galaxies.
The Planetary Nebula Spectrograph, PN.S, designed and built by an international
consortium with groups from Australia, The Netherlands, Italy, the UK and
the USA, is an instrument that has been designed with a very specific scientific
objective in mind. This slit-less spectrograph produces counter-dispersed
images of galaxies in the OIII line. This setup allows very easy and efficient
detection of planetary nebulae in galaxies through their emission line nature.
The images obtained provide not only the position of the PNe, but also the
radial velocity of the objects that can then be used to study the dynamics
Apart from these new visitors, also other visiting instruments that had
been to the telescopes before, like the MUSICOS fibre-fed echelle spectrograph,
the CIRSI panoramic IR camera, and the Texas-Tromso Photometer, returned to
the ING telescopes.
Figure 3. The Planetary Nebula Spectrograph fully
assembled and integrated with the WHT, and EEV CCDs and controllers mounted
on each arm of the spectrograph. [ JPEG | TIFF ]
Instrumentation development activities now strongly involve ING’s engineers
and astronomers on La Palma, a trend that has become more apparent during
the reporting years. Reorganisation of the operational activities has enabled
ING staff to gradually become more involved in development projects than used
to be the case. The following main projects came to fruition.
Early 2000 saw the completion and commissioning of ING’s new infra-red imager,
INGRID, for the WHT. The system performed well from the very start. INGRID
is made available at a new port on the Cassegrain focus and is also used as
the premier imaging system for adaptive optics. This camera at its heart has
a Rockwell 1024 by 1024 pixel HgCdTl array detector covering a field of over
four minutes of arc. It has been very popular within the user community, judging
from the number of applications and post-observing feedback received. In
particular the field of view has proven to be an attraction to observers.
Figure 4. Left: INGRID
mounted on one of the WHT folded Cassegrain foci (top right). The instrument
on the Cassegrain focus is SAURON. [ JPEG | TIFF ] Right: This image acquired
using INGRID on the first nights is a J-band image of M95. The inset on the
right shows the nuclear ring of enhanced star formation. [ JPEG | TIFF ]
A second important project carried out at the ING was the design and construction
of a new fibre module for the AUTOFIB multi-object fibre spectrograph in the
prime focus of the William Herschel Telescope. AUTOFIB has considerably increased
in popularity, most likely due to the fact that this instrument fulfils a
pivotal role for spectroscopic follow-up observations of ongoing imaging
surveys such as the ones being conducted at the INT. The new fibre module
with smaller, 1.6 arcsec diameter fibres has the advantage of reduced sky
background contamination and higher throughput. Design and manufacturing work
on the new fibre module was fully carried out at ING. A further enhancement
of the fibre spectrograph has been initiated, with the design and construction
of a new spectrograph camera that will allow imaging more fibres and deployment
of larger format CCDs.
Figure 5. Left: Alignment of fibres
into micro-lens finger holder at ING. [ JPEG |
TIFF ] Right: The Small Fibre Module at WHT
prime focus. [ JPEG | TIFF
Arguably the most important development project that came to fruition was
the technical commissioning and first science observations of the common-user
adaptive optics system for the WHT, NAOMI. The Adaptive Optics (AO) programme
is a corner stone development area for the WHT. The 4-m class telescopes will
more readily be able to effectively exploit AO techniques at relatively short
wavelengths and over moderately wide fields than the larger telescopes, in
particular on a good observing site such as La Palma. The WHT AO system was
designed and built by a team from Durham University and the UK-Astronomy Technology
Centre in Edinburgh. The advent of NAOMI required a range of modifications
and improvements to be made to the Nasmyth focal station and telescope performance
in order to make the telescope ready for the 0.1 arcsecond world of adaptive
During pre-commissioning tests diffraction-limited images were readily obtained
in the J, H and K bands with a small pinhole illuminating the focal plane.
And also on celestial objects in the K band the diffraction limit was reached.
Most of the commissioning goals were met, proving basic functionality of
the system. Particularly impressive was the quality of optical alignment
achieved with the modular NAOMI design and the success of largely automated
methods for determining and correcting for so-called non-common path error
(differential optical aberrations between wavefront sensor camera and science
camera). The complex interplay between the segmented deformable mirror, the
fast steering mirror, and the telescope tracking was achieved reliably.
Following initial commissioning in 2000, further on-sky tests have focussed
on optimising and characterising system performance. Key achievements included
regular diffraction limited 0.12 arcsec FWHM performance in the K band, closing
the loop on a 15th-mag star, and automatic dithering with the AO loop closed.
In September 2001 tests were conducted to gauge NAOMI's performance in the
optical, in preparation for the OASIS integral-field spectrograph that will
come to the WHT in 2003.
Figure 6. Left: H-alpha image of globular
cluster M13 obtained using NAOMI. The FWHM has been improved from 0.8 arcsec
(natural seeing) to 0.4 arcsec, allowing many faint stars to be resolved.
The image was taken during September 2001 tests of NAOMI’s performance at
optical wavelengths, and provides a realistic outlook of the AO potential
at the William Herschel Telescope. Given that the median natural seeing on
La Palma is about 0.7 arcsec, an image quality of ~0.3 arcsec in the R and
I bands should be achieved regularly. [ JPEG
| TIFF ] Right: NAOMI in GHRIL, with INGRID in
the foreground. [ JPEG | TIFF ]
Further development of the adaptive optics programme at the WHT includes
deployment of a coronagraph (OSCA), built at the University College London,
and of an integral field spectrograph (OASIS) in collaboration with Centre
de Recherche Astronomique in Lyon, France. Both instruments will provide
important new science capability to the adaptive optics system and are expected
to be commissioned in 2003.
The NAOMI AO instrumentation relies on natural guide stars to measure wavefront
distortions. Optimal exploitation of AO would require the deployment of artificial
guide stars produced by a laser beam, as this would provide nearly full sky
coverage. Large sky coverage enables a much wider range of astronomical applications
of adaptive optics to be carried out. A sodium laser produces a fluorescent
spot high in the Earth’s atmosphere, at an altitude of approximately 90km
that can then be used as an artificial star. In preparation for possible
future sodium beacon deployment on La Palma a study has been completed to
investigate whether the atmospheric conditions above the observatory are
suitable for this technique and to learn about the technical complexities
of sodium laser guide star deployment. This programme, led by the Imperial
College in London, resulted in a number of laser firings during several nights
over the period of one year. The very successful trials gave invaluable information
and experience on both technical and atmospheric parameters. For instance
the tests allowed measurement of the temporal variation of the mesospheric
sodium layer thickness and profile, as is shown in the adjacent figures.
Figure 7. Left: Sodium laser beam
projected in the sky. Clearly visible are the low altitude Rayleigh back
scatter plume and the sodium 'spot' at some 90 km above the observatory.
[ JPEG | TIFF ] Middle: The Sodium spot
at 90 km as seen from the Jacobus Kapteyn Telescope. Due to projection effects
the spot is seen elongated against the sky. [ JPEG | TIFF ] Right: Temporal and
spatial profile of the sodium spot during one observing night. [ JPEG | TIFF ]
An exciting instrument under development at the Instituto de Astrofisica
de Canarias that will likely serve a large user community in the future is
the LIRIS IR spectrograph and imaging system. This versatile system, designed
for the Cassegrain focus of the WHT, will be capable not only of high quality
imaging from 0.9 to 2.4 micron, but also of long-slit and multi-slit spectroscopy,
coronography and polarimetry. Commissioning is expected to take place in
On the 2.5-m Isaac Newton Telescope survey activities with the Wide Field
Camera continued to fulfil an important role in the scientific exploitation
of this telescope. Survey proposals ranged from deep galaxy surveys to a
census of the Local Group and an extensive investigation of time-dependent
phenomena. Sky coverage of the main science programme of the survey passed
the 150 square degrees mark.
The first round of proposals for the Wide Field Survey has completed a full
three years, and a second call for proposals was send out as a continuation
of the scheme. Following this second announcement of opportunity for Wide
Field Survey activities, six proposals were selected by the time allocation
committee. The principal investigators and the titles of the selected proposals
Dalton (Oxford), The Oxford deep WFC survey
Davies (Cardiff), Multi-coloured large area survey of the Virgo cluster
Van den Heuvel (Amsterdam), The faint sky variability survey
McMahon (Cambridge), The INT wide angle survey
Walton (Cambridge), The Local Group census
Watson (Leicester), An imaging programme for the XMM-Newton serendipitous
X-ray sky survey
Clearly the offer of survey time has again inspired the principal investigators
to request large blocks of observing time over several semesters that would
otherwise be difficult to get approved through the normal time allocation