  The search for earth-like exoplanets with the Doppler radial velocity
technique is an extremely challenging and multifaceted precision spectroscopy
problem. Currently, one of the limiting instrumental factors in reaching the
required long-term $10^{-10}$ level of radial velocity precision is the
defect-driven sub-pixel quantum efficiency variations in the large-format
detector arrays used by precision echelle spectrographs. Tunable frequency comb
calibration sources that can fully map the point spread function across a
spectrograph's entire bandwidth are necessary for quantifying and correcting
these detector artifacts. In this work, we demonstrate a combination of laser
frequency and mode spacing control that allows full and deterministic
tunability of a 30 GHz electro-optic comb together with its filter cavity.
After supercontinuum generation, this gives access to any optical frequency
across 700 - 1300 nm. Our specific implementation is intended for the comb
deployed at the Habitable Zone Planet Finder spectrograph and its near-infrared
Hawaii-2RG array, but the techniques apply to all laser frequency combs used
for precision astronomical spectrograph calibration and other applications that
require broadband tuning.
