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R. D. Blandford, L. V. E. Koopmans, (Caltech)
As currently configured, SNAP should cover an area of sky to sufficient depth to observe tens of thousands of strong (ie multiple-imaging) gravitational lenses. This could provide an unprecedented database for performing cosmography, studies of large scale structure and galactic structure.and should complement the weak lensing program which will concentrate on larger scales. The challenge will be to recognize multiple imaging efficiently in an unbiased way and to organize effective follow up so as to obtain spectroscopic redshifts and monitor variable sources, when appropriate. Experience with the CLASS radio survey and the CASTLES program will be invaluable as we transition from the detailed study of a few tens of strong lenses through the ACS ultra-deep, deep and wide surveys (which should yield hundreds of examples of multiple imaging) to the larger samples envisaged from SNAP. New approaches to data analysis will be needed and coordinated planning with other proposed large survey instruments, like SKA, will be essential.