Despite recent advances in the study of extra-solar planets the detection of reflected light from planetary atmospheres remains a major goal. For the so-called hot-Jupiters, which are unlikely to be spatially resolved from the central star in the foreseeable future, very high sensitivity measurements are required to detect the reflected signal from the very much larger direct starlight. We describe an optical photo-polarimeter designed to have a polarization sensitivity of at least 1 in $10^6$ and some early observations made in an attempt to detect the polarization signature of $\tau$ Boo b. We discuss the role of such an instrument for the planned ELTs.

Cool, extrasolar gas giants similar to Jupiter and Saturn in our own Solar System should be detectable by virtue of the light they reflect in the optical and near-infrared with the next generation of Extremely Large Telescopes (ELTs) equipped with adaptive optics systems. Broad band imaging or very low-resolution spectra should then enable the characterization of the orbit, mass, atmospheric scattering properties, and presence of large rings in these gas giant analogues.

Various projects to find planets or entire planetary systems around main sequence stars in the solar neighborhood are presently under way. When ELTs will be operational, there will be literally thousands of confirmed planetary systems including spectro-photometric detections. At this point it becomes inevitable to consider the next logical step: the spectroscopic analysis of the atmospheres of these planets. High-resolution spectroscopy, i.e. resolving $v \times \sin (i)$ of these planets, in the wavelength regime of 950-5500nm is a powerful and promising tool. In view of the obvious contrast problems in detecting such planets non-LTE features are specifically targeted. Sensitivity estimates for the detection of the non-thermal OH glow in oxygen-bearing atmospheres are given. With 8m-class telescopes such a search is impossible, but a dedicated spectrograph, e.g. at the projected ESO 100m OWL telescope could detect Earth-like planets at a distance of ${\approx} 10$ parsec. A conceptual design for a dedicated spectrograph, NOCTUA, is presented. In case of ELTs of smaller size the science case changes and the instrument requirements have to be adjusted. Preparatory work with CRIRES, ESO's Cryogenic Infrared Echelle Spectrograph on the VLT at $\frac{\lambda}{\Delta \lambda} \approx 10^5$ as well as other science cases are shortly discussed.

The extreme contrast in mass and luminosity between the extra-solar planets and their host stars make detailed studies of these planets very challenging. In particular, direct observations of extra-solar planets is still beyond the capabilities of the currently available instrumentation, save for perhaps a few extreme cases of very young and massive planets at large distances from the central star. While progress in instrumentation might allow significant progress in detection capabilities either with the 8 and 10-m ground-based telescopes (Planet Finder instruments on the VLT and Gemini) or with the next generation space telescope (JWST), imaging of extra-solar planets over a wide range of parameters, and possibly down to terrestrial planets, will require extremely large ground-based telescopes like OWL or dedicated space instrumentation (TPF or Darwin for instance). We outline here the scientific objectives of EPICS, the OWL Earth-like Planet Imager and Spectrograph, summarize the corresponding high level requirements, present the foreseen observing modes and give a first estimate of its performance.

Brown dwarfs and very low-mass stars are likely to harbour planetary systems with rocky planets. We discuss the possibility of detecting them using accurate radial velocity measurements with a cross-dispersed high-resolution spectrograph coupled to a ground-based extremely large telescope.

The detection of telluric extra-solar planets implies an extremely high contrast long exposure imaging capability at near-infrared and probably visible wavelengths. We present here the core of any Planet Finder instrument which is the extreme AO sub-system. The level of AO correction directly impacts on the exposure time required for planet detection. The extreme adaptive optics system has to correct for the perturbation induced by the atmospheric turbulence as well as for the internal aberrations of the instrument itself. An example of application is proposed in the frame of the EPICS project (XAO system for the ESO OWL telescope).

The future planning working group of the optical and infrared astronomy community of Japan completed its two-year study to yield a concrete plan for ground based telescopes and space missions for the coming decades. The R&D issues towards the realization of extremely large telescopes reported in this paper include a novel optical design, development of new ceramic mirrors, high precision grinding approach to reduce the involved cost and time for fabricating aspheric segmented mirrors, and conceptual studies of instruments.

The present paper is essentially a slightly updated version of the paper presented in the workshop “Instrumentation for Extremely Large Telescopes” held at Ringberg Castle, Bavaria, 25-29 July 2005.

This report is a general introduction on Chinese large telescope projects. It includes the ongoing project Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), and three projects which have reviewed by Chinese government recently: Five-hundred-meter Aperture Spherical (radio) Telescope (FAST); Space Solar Telescope (SST); Hard X-ray Modulation Telescope (HXMT). These three projects have finished their feasibility studies and development of key technologies. They are very likely to be approved by the Chinese government in 2006. Besides these large telescope projects, the site survey in Western China for large telescopes in optical, infrared, sub-millimeter and millimeter astronomy, the preliminary study on Chinese future giant optical/infrared telescopes, and a future extremely large wide field telescope are also briefly introduced.

The project of the Russian 6m BTA telescope reconstruction was cancelled in 2004 because of financial problems. In the beginning, it was planned to replace the existing 42 ton parabolic main mirror by a new one of 8m diameter using the Zerodur blank provided by the Germain company Schott.

Russia still possesses a high potential in the development of large-scale optics and mechanics. A new 25m telescope with the segmented mirror was the subject of wide speculations. Strange as it may seem, the country with the world largest territory has no good site for a large astronomical observatory. Any project of the national observatory is therefore faced with the necessity of looking for a foreign partner. We are also studying the possibility of joining one of the large international projects, including the ESO projects OWL, ALMA and others. At the same time, work on a few Russian space astronomical missions is going on well.

We describe how the Virtual Observatory (VO) projects in Europe, the USA, Japan, and elsewhere are meeting the challenge of providing simple and efficient access to the data from the world's observational facilities, together with applications and computational resources required to support the analysis of this data. We note the pan-European Euro-VO project and its technological development VO-TECH project which are now in the process of designing the framework for comprehensive access to emerging high data volume facilities such as ESO's VISTA infrared survey telescope.

Science drivers from major new astronomical missions are helping to define the development of the VO. Scientifically this is in terms of developing systems able to meet the demands of the main science programmes shaping the ELTs. VOs must be able to handle the large data streams from the complex multiplexed instruments on the ELTs, and provide access to applications required to analyse/interpret the data. VOs must enable the effective distribution of ELT data to the global community.

Conversely, the rapid development of the Virtual Observatory, offers opportunities for major new projects such at the ELTs. This could be: in the design of their down stream data-flow systems; in terms of opening up access to ‘real-time’ availability of ancillary data flows; in multi-wavelength observational programmes.

We highlight these areas, and give some specific current examples of early VO usage in delivering science from, e.g. the mining of deep multi-wavelength surveys to study the high redshift universe.

The extremely large telescopes (ELTs) are built at huge financial cost and usually involve partnership among several bodies/nations. Consequently and naturally, telescope time allocations in many, if not most, of such telescopes are based either directly or indirectly on the monetary contributions of the partners. This paper examines the economy, sociology, science and politics of the ELTs and their implications for the astronomers and/or astronomy in poorer developing nations.

The scientific goals for the TMT (Thirty Meter Telescope) are consistent with all the objectives outlined by the top level astronomy review committees in both Canada and the United States. In addition to powerful seeing-limited instruments, TMT will include instruments that will take advantage of the full diffraction-limited performance of a 30m telescope at wavelengths $\gt 1 \mu {\rm m}$. This will enable TMT to meet the challenges presented by the scientific requirements and will provide full complementarity with future project like JWST and ALMA. This paper presents a brief review of the status of TMT and an overview of the instruments and their adaptive optic systems.

The original Magellan partner institutions and the Smithsonian Astrophysical Observatory, Texas A&M University, and The University of Texas at Austin have undertaken to construct an extremely large telescope in Chile. The Giant Magellan Telescope is built around seven 8.4m borosilicate honeycomb mirror segments, six of which are off-axis. The collecting area is equivalent to that of a filled aperture 21.5m in diameter, the angular resolution is equivalent to a filled 24.4m telescope. The telescope mount is highly compact and delivers light to the focal plane in two reflections. Instruments are mounted at either a low-background straight Gregorian focus, or to one of several folded Gregorian foci behind the center primary mirror segment. A set of candidate first generation instruments has been defined and conceptual design studies are underway. The first off-axis primary mirror segment has been cast and will soon be polished as part of a proto-typing program. The current schedule calls for first light in mid 2015. This contribution describes the telescope and the considerations that led to its design.

The 100 m OWL ESO Concept Study has undergone a full review early November 2005. The development of the concept, the conclusions of the review panel and the planned post-review actions for the European Extremely Large Telescope (ELT) to be built by ESO in the next 10 years are presented and discussed.

For a European ELT, we discuss science requirements and technical options. Science includes from the solar system to the first stars and galaxies. ELT and instrument needs are commented. Design options are discussed for the primary mirror, its segmentation and shape, and an adaptive secondary mirror. Adaptive optics and enclosure are commented.

We review the need for technology developments to meet the science cases that have been assembled for optical and infrared telescopes from 20 to 100 metres. Novel technologies can make an impact on the scientific capabilities of these ELTs, make them more affordable and decrease the operating costs. We consider those technologies highlighted by design studies and technology roadmapping exercises on both sides of the Atlantic, with particular emphasis on instrumentation. We do not consider adaptive optics (AO), which is covered by Ellerbroek & Hubin (this volume). Finally, we recommend a joint technology development programme to enable a world-wide suite of ELTs to be built.

The ongoing conceptual design activities for the Thirty Meter Telescope (TMT) illustrate many (if not virtually all) of the advanced instrumentation technologies under consideration for future extremely large telescopes. First light capabilities must be based upon credible extrapolations of existing systems and components, while potential upgrades and follow-on systems should explore the full range of advanced and innovative technologies currently proposed for scientific instrumentation and adaptive optics (AO). An affordable technology development program must then be implemented which balances these conflicting objectives.

In this paper, we outline the range of innovative AO component technologies now under discussion for TMT, and describe some of the contracts and studies comprising our AO development program. Components that require advances include piezostack and MEMS deformable mirrors; adaptive secondary mirrors; fast, low noise detectors for both laser- and natural guide star wavefront sensing; guidestar laser sources; and processing electronics for the implementation of AO control algorithms. Instrumentation studies are also underway that investigate issues related to the huge size of seeing-limited instruments; large gratings; integral field spectroscopy; detectors; and advanced techniques for sky subtraction.

I summarise the ELT requirements derived from the science cases in the area of galaxy formation/evolution and cosmology. This summary is based on the talks, posters and discussion in parallel Session A of this meeting, but also makes use of various publically-available ELT science case documents. Topics covered include studies of black holes, dark matter, properties of galaxies at a range of redshifts (including the first galaxies to form), fundamental constants and cosmology.

ELTs will bring galaxies within 5 Mpc or more “as close as the Magellanic Clouds”. This is why stellar populations is such an exciting subject for ELTs. We can resolve galaxies into stars and learn their history (1) from the “fossil record” of old stars and (2) looking back in time. The confrontation of these two views will bring important new insights in the star formation history of galaxies and stellar evolution, at the same time.

We summarise the science cases for an ELT that were presented in the parallel session on the intergalactic medium, and the open discussion that followed the formal presentations. Observations of the IGM with an ELT provides tremendous potential for dramatic improvements in current programmes in a very wide variety of subjects. These range from fundamental physics (expansion of the Universe, nature of the dark matter, variation of physical constants), cosmology (geometry of the Universe, large-scale structure), reionisation (ionisation state of the IGM at high $z\ge 6$), to more traditional astronomy, such as the interactions between galaxies and the IGM (metal enrichment, galactic winds and other forms of feedback), and the study of the interstellar medium in high $z$ galaxies through molecules. The requirements on ELTs and their instruments for fulfilling this potential are discussed.