The eye of the beholder: designing the OWL

Abstract

Preliminary requirements and possible technological solutions for the next generation of ground-based optical telescopes were laid down at ESO in 1998. Since then, a phase A study has been commissioned, the objective of which is to produce a conceptual design compatible, to the maximum possible extent, with proven technology, and establish realistic plans for detailed design, site selection, construction and operation for a 100-m class optical, diffractionlimited telescope. There was no doubt about how daunting such a challenge would be, but, somewhat surprisingly, it turns out to be firmly confined to adaptive optics concepts and technologies. The telescope itself appears to be feasible within the allocated budget and without reliance on exotic assumptions. Fabrication of key subsystems is fully within the reach of a properly engineered, industrialized process. A consolidated baseline is taking shape, and alternative system and subsystem solutions are being explored, strengthening the confidence that requirements could be met. Extensive development of wavefront measurement techniques enlarges the palette of solutions available for active wavefront control of a segmented, active telescope. At system level, ESO is developing enabling experiments to validate multi-conjugate adaptive optics (MAD for Multi-conjugate Adaptive optics Demonstrator) and telescope wavefront control (APE, for Active Phasing Experiment).

Comparison of measurements of the outer scale of turbulence by three different techniques

“…A finite outer scale has implications for interferometry as well. 9 -11 With the current interest in the design of extremely large ground-based optical and infrared telescopes, [12][13][14][15][16][17][18] reliable estimates of the true size of the outer scale have assumed considerable importance.…”

Control and alignment of segmented-mirror telescopes: matrices, modes, and error propagation

“…[1][2][3][4][5][6][7] The majority of these telescopes involve a highly segmented primary mirror, with several hundred up to even a few thousand segments. The optimal number of segments used to fill a particular aperture size is the result of a key design trade-off: Larger segments are in general more difficult to fabricate whereas smaller segments are more difficult to align and control, principally as a result of their larger numbers.…”

Site selection for OWL using past, present, and future climate information

“…The reanalysis products are known as ECMWF Reanalysis 20 (ERA) and NCEP/NCAR Reanalysis 21 respectively. These reanalysis products are freely available to the scientific community for research purposes, and are available for download on the internet 1,2 . Our study uses data from both sets of reanalyses, in order to be as comprehensive as possible.…”

“…The construction of such a telescope would constitute a major engineering challenge 3 , but current estimates indicate that the cost may be met within a budget of €1 billion 1,4,5 . A decision on whether to go-ahead with OWL project is due sometime in 2005, and a search for the best possible site in the world is well underway 6,7 .…”

“…The European Southern Observatory (ESO) is presently undertaking concept studies on the possibility of a new Overwhelmingly Large (OWL) 100-metre diameter optical telescope 1,2 . The construction of such a telescope would constitute a major engineering challenge 3 , but current estimates indicate that the cost may be met within a budget of €1 billion 1,4,5 .…”