The Scientific Requirements for Extremely Large Telescopes Plenary talks:Review of scientific achievements of current 8-10m telescopes (Longair)ELT Science: Exoplanets & SF, Stellar Pops, IGM, Galaxies & CosmologySynergies: SKA, JWST, Herschel/ALMAELT projects I: Overview, Sites, Detectors, Instruments, Adaptive OpticsELT Projects II: TMT, GMT, OWL, Euro-50, Novel Techniques, Surveys & Ops.

Parallel SessionsScience Working Groups: Exoplanets & Star Formation, Stellar Populations, Intergalactic Medium & Large Scale Structure, Galaxy Formation/Evolution & Cosmology The Diversity of Projects Worldwide

Discussion

IAU Symposium 232, Cape Town, 14-18 November

Frequently Expressed ViewsNeed instruments to cover wide range of observational parameter space open to discoveries and a broad astronomical programme

Need both large collecting area and angular resolution (and FOV?)

Each ELT project should take into account what others are doing for instrumentation (overlap should be avoided, while competition is maintained)

Some Other Comments at the MeetingNo significant break points (except Virgo? - for which D > 40m?)Mid infrared for star formation - (implications for site)ALMA synergy southern hemisphereImportance of polarizationimportance of calibrationNeed end-to-end operationsKeep options open for new instrumentsLimitation on high contrast imaging due to segmented mirror(?)Revolution in NIR spectroscopy - OH suppression techniques

Some Points of Discussion at the MeetingStress FOV over telescope aperture and resolution?How many astronomical programmes need AO?Should the different ELTs have different/complementary instruments?Should there be 2-3 specialized ELTs? (eg high and low altitude?)Include parallel observational capabilities?Will ELTs do surveys?