Name: Jacques Beckers
Institution: University of Washington

University of Washington

Astrolunch

Abstract:
I am aware of at least 8 projects for Extremely Large Telescopes (or ELTs) that are currently on the drawing board. These are telescopes with mirror diameters ranging from 22 to 60 meters. ELTs aim at collecting as many photons as feasible and putting them in as sharp an image as possible using the rapidly evolving technique of adaptive optics.

Some of the scientific goals for ELTs need very high resolution optical spectrographs Conventional techniques used until now for constructing those devices result in dimensions comparable to the sizes of their host telescopes. The resulting large sizes for ELTs cause technical problems not the least of which are the control of gravity and thermal flexures needed to achieve wavelength stability.

As part of the 50-meter Euro50 telescope project I explored ways of decreasing the spectrograph size while at the same time increasing its spectral resolution. The technique proposed uses "pupil slicing" combined with adaptive optics. The resulting spectrograph has a size of only a couple of meters. The spectral resolution aimed at is > 100,000 and can be made to exceed 500,000. That is enough for quality studies of the interstellar medium in our and nearby galaxies and of the intergalactic medium at high red shifts using QSO absorption line systems. Applications also include the search for planets around other stars and the study of the atmospheres of those planets.