Annu. Rev. Astron. Astrophys. 1992. 30: 311-358
Copyright © 1992 by . All rights reserved

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Over the next few years, we can look forward to several new instruments that will be well suited to studying different aspects of the gravitational lens problem. At radio wavelengths, the VLBA should produce far more detailed maps of the radio rings as well as the radio jets in Q0957+561 and Q2016+112, which will motivate correspondingly detailed modeling. The enlarged MERLIN radio telescope may have just the right angular resolution to find several more examples of galaxy-imaged compact radio sources. In the optical, a repaired and fully operational Hubble Space Telescope will have the angular resolution to locate intervening galaxies, and the Keck Telescope will be particularly important for faint object spectroscopy. Detector advances in CCDs and infrared arrays also promise to make a substantial difference. Because of these and several other developments, the observational future looks bright.

If we can learn anything from the history of cosmology, it is that it is much easier in theory than in observational practice to make secure, quantitative deductions about the large scale structure and the evolution of the universe. By contrast, if the last decade's progress in understanding gravitational lenses can teach us anything, it is that we have usually been too conservative in our anticipation of novel phenomena. It will be fascinating to see which of these two opposing trends dominates over the next decade.


This work was supported in part by NSF grants AST 89-17765 (RB) and AST 91-09525 (RN). We thank George Efstathiou, Emilio Falco, Bernard Fort, Paul Hewett, Chris Kochanek, Charles Lawrence, Jordi Miralda-Escudé, Bohdan Paczynski, Kevin Rauch, Sjur Refsdal, Rudy Schild, Peter Schneider, Jean Surdej, Sylvanie Wallington, and Joachim Wambsganss for comments on the draft manuscript. We are grateful to Helen Knudsen and Rosanne Scholey for bibliographic assistance.

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