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Octave-spanning, mode locked femtosecond laser frequency combs convert the most precise instrument available today - the atomic clock - to the frequency domain, providing an equally precise yardstick for wavelength calibration, potentially 1:10^15. Precision at this level enables astronomical radial velocity measurements to 1 cm/sec over decadal time scales. This capability will make it possible to search for earth-like planets orbiting solar type-stars in the habitable zone and to measure the expansion of the universe directly, as well as to explore the local distribution of dark matter and to search for variations of fundamental constants over cosmological time scales. I discuss the techniques, status and potential of this instrumentation as well as ongoing and future observational programs, especially with G-CLEF, an echelle spectrograph being studied for the GMT. |