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ING Vision 2010 - 2020
Marc Balcells, Chris Benn, Don Carlos Abrams
Our strategic vision of the WHT for the next decade is that of a telescope that operates a
range of instruments offered for
classical observing on a large fraction of the year,
while we increase the time devoted to surveys with key instruments
with strategic importance to our communities - instruments where a 4m telescope delivers
more science than larger telescopes. Current discussions suggest that such strategic instrument
a wide field multi-object spectrograph at the WHT prime focus, designed for efficient
follow-up of galactic and extragalactic surveys that will become available in the coming years.
The ING will continue to provide valuable access to the Northern sky to our communities.
We will enhance our visitor instrument programme, and to offer
small fractions of WHT time for the development of technologies useful for E-ELT
instrumentation. Our developments will take into account recommendations of
European review committees on intermediate-size telescopes.
An evolving astronomical landscape
Twenty-five years after the inauguration of the INT and JKT, and 20 years after WHT started science operations, the Isaac Newton Group of Telescopes (ING) is discussing its role for the coming decade. The ING telescopes, thanks to the vitality of the astronomical communities served by them, have amply fulfilled the ING mission of fostering major advances in our knowledge of the Universe. Owing to a versatile set of instruments, and to our commitment to a classical, visitor-oriented operating mode, world-class science has emerged in virtually all areas of astronomy. Our focus on PI science tailored to small groups has meant that the majority of our astronomers, residing in University groups, have had regular access to world-class observational facilities. By welcoming visitor instruments, ING has facilitated the development of innovative instrumentation, thereby contributing to the training of generations of instrumentalists. The multi-national nature of our clients has fostered international collaboration and has decisively contributed to the emergence of Spanish astronomy in the past two decades.
The global astronomical landscape has evolved tremendously during the thirty years throughout which the International Agreements have articulated astronomy in the Canary Islands. As many as twelve optical-infrared telescopes with apertures above 8m are in operation worldwide. Plans are underway in the USA and in Europe for the construction of the next generation of giant telescopes, with apertures of 30m to 42m, which could start observations within one decade. The cost of these larger facilities, and that of projects at other wavelengths on the ground (ALMA, SKA) and in space (JWST, LISA) forces the communities to re-evaluate the roles of the smaller facilities in order to open the way for the larger telescopes.
The following sections portray our vision of the role the WHT should play in the coming decade. Our challenge is to remain a world-class facility, while maintaining the current level of service to the community and the cost effectiveness of our operation for our funding agencies.
The WHT, like other 4m-class telescopes, provides observing capabilities that larger telescopes cannot deliver
Both the ING Board and the ING Science Advisory Committee concur that 4m telescopes have an important role to play among 10m-class telescopes, namely to deliver an efficient capability for wide-field (WF) astronomy. Typical fields of view (FOV) on 10m telescopes are below 20 arcmin in diameter. On 4m telescopes, FOV can reach diameters of 2 degrees at prime focus (PF). Survey speeds are greatly enhanced, both in imaging and multi-object spectroscopy (MOS). We are in agreement with the conclusions of the OPTICON-ASTRONET-led ETSRC Infrastructure Roadmap for European medium-sized telescopes. In this context, the WHT has an important role to play as a 4m complement of the 10m GTC on the ORM.
The three ING partners are all members of ESO, and ESO provides ample access to observational capabilities in the Southern sky. The ING has a crucial role to play in providing access to the Northern sky. Access to the Northern sky is crucial for several science areas. These include the Northern Milky Way, nearby galaxies such as M31, M32 and M33, Local Group dwarf spheroidals, the Coma cluster, follow-up of radio surveys in the North such as LOFAR, and important cosmological fields such as the GOODS-North field, the Lockman Hole and the ELAIS fields. Of strategic importance, access to the Northern sky is essential for follow-up of space-based surveys such as GAIA and Herschel in the North, in support of our communities' investment in space astrophysics.
WEAVE, a wide-field multi-object spectrograph for the WHT
It has become clear in recent years that, among WF instruments, our communities have a strong interest in a WF MOS. The rationale for this is based on the fact that, in the coming years, many imaging and photometric surveys will be carried out on a variety of platforms at a wide range of wavelengths. Examples include the VST and VISTA surveys, the Pan-STARRS maps of the sky, the GAIA map of the Milky Way, and the LOFAR radio survey, in addition to the ongoing UKIDSS surveys. For all of these, obtaining useful physical information from the sources requires extensive optical spectroscopy to obtain redshifts and physical characterization of millions of targets. With a new corrector, now in the design stage, the WHT will deliver a FOV of 2 degrees in diameter. Due to this, the ING is proposing the construction of WEAVE, a wide-field MOS at WHT. The science cases call for a spectrograph fed with 1000 fibres and delivering spectra of resolving power of 5,000 covering from 370 nm to 1000 nm. A high-resolution mode will also be available, with resolving power 20,000 over a smaller wavelength range. WEAVE will provide for single-fibre input as well as mini-IFUs and a monolythic IFU. A science team and an instrumental team will develop the instrument design and construction. ING is working with the WEAVE team to ensure support from the funding agencies for the project, and to expand including non-ING partners to make WEAVE and its scientific exploitation a truly European project. Updated information on this project can be found at the WEAVE web site.
The Harvard-led HARPS-NEF high-resolution stabilized spectrograph was part of our strategy of providing the WHT with competitive, front-line instrumentation. Funding issues prevented HARPS-NEF from coming to WHT. It is our understanding that the instrument, now named HARPS-N, is being built by a consortium led by Observatory of Geneva and is planned for deployment at TNG. We regret not being able to host HARPS-N on the WHT, and wish the team full success in the detection of planets by the radial velocity technique.
Balancing classical observing with large surveys
The ING will strive for a middle ground approach between allocating time for classical, TAC-based time allocation to small-size proposals, and large allocations to survey-type science. Whilst the former has been at the root of ING's past successes, and oversubscription factors of 4 indicate that this mode of observation is in much demand, it is only through large time allocations that the full power of some of our instruments can be harvested and solutions for key astrophysical questions can be sought. The spectroscopic follow-up to large surveys which we suggest above is one such example. The exact balance between the two observing modes is a matter of debate, and indeed it is the communities we serve who have to decide the amount of time allocated to surveys.
How many instruments
A diversity of common-user instruments is a natural wish of classical observing, and the WHT has excelled in this regard in the past. At the same time, more instruments imply greater maintenance costs. Furthermore, having more instruments results in each instrument sitting unused in storage for a larger fraction of each year. Obtaining full benefits from the construction of forefront, expensive instruments, requires generous access to telescope time. For all of these reasons, it is likely that ING will reduce the number of supported common-user instruments in the near future. Instrument selection will be guided by the statistics of instrument requests by our users, among other considerations. For the past 5 years, 50% of all requested time at the WHT has been for ISIS or LIRIS, which rightly qualify as the work-horse instruments of the WHT.
Enhancing the visitor instrument programme
In our view, the ING mission of providing telescopes for world-class astronomical research is strongly served by continuing our successful visitor instrument programme. Within this programme, small groups have been able to complete the entire instrument building cycle, from idea through design and construction to exploitation on a world-class telescope, in the time span of a few years. Over the years, this programme has fostered the training of generations of instrumentalists; today it is these scientists who are leading the design of the complex instruments needed for future giant telescopes. Furthermore, data from visitor instruments have led to some of the most highly cited papers coming from the WHT. And it is a common remark from teams who have deployed their instruments at the WHT that their programme could not possibly have been carried out at any other major observatory to which they have access. For these reasons we believe that maintaining and enhancing the visitor instrument programme is of immense benefit to our communities, and we plan to do so in the future.
Through our visitor observer, classically scheduled mode, and our resident student programme, students and young astronomers gain a direct exposure to optical-infrared observing. We believe this is an important contribution of ING to present and future astronomy, and we plan to continue our programme.
Use of the WHT for technology development
We believe that our mission of supporting forefront astronomical research benefits from our offering a fraction of WHT time to activities aimed at developing technologies that do not immediately yield astrophysical knowledge but which will be used in future instruments. In particular, we plan to facilitate technology development aimed at instrumentation for E-ELT.
European-wide rationalisation of observing capabilities
European astronomy holds an important potential for better coordination of national-level strategic plans. For medium-size telescopes, such coordination is fundamental if we are to survive under the funding pressure driven by the larger facilities. ING is engaged in the OPTICON-ASTRONET-led ETSRC study, whose final report is expected in the first quarter of 2010. ING already has instrument and observing time-sharing experience, which we are eager to contribute in order to make the process a success. For the multi-object spectrograph we plan to take into consideration the recommendations of the ETSRC and its MOS working group.
The Adaptive Optics programme at the WHT
Promoting wide-field spectroscopy represents a change of strategic direction for ING. In the past
decade, ING has focussed on developing technologies and observing capabilities
high-spatial resolution imaging
and integral-field spectroscopy
based on natural guide star (NGS) and laser-assisted (LGS) adaptive optics (AO). While
the WHT ground-layer laser system
was a good choice when initially planned, it is no
longer competitive now when several 8 and 10m telescopes have sodium-layer laser systems. Our
AO systems will continue operational with a priority below that of other
instruments. We note that the investment in AO has led to a high knowledge level on AO systems,
which will come in handy for technology developments aimed at the E-ELT, as described above.
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