  Future space-based direct imaging missions are poised to search for
biosignatures in the atmospheres of potentially habitable planets orbiting
nearby AFGKM stars. Although these missions could conduct a survey of
high-priority target stars to detect candidate Earth-like planets, conducting a
precursor radial velocity (RV) survey will benefit future direct imaging
missions in four ways. First, an RV survey capable of detecting signals as
small as 8 cm/s over timescales of a few years could discover potentially
habitable Earth-mass planets orbiting dozens of nearby GKM stars accessible to
space-based direct imaging. Second, RVs will improve scheduling efficiency by
reducing the required number of revisits for orbit determination, and revealing
when a planet of interest is most observable. Third, RV observations will
reveal the masses of gas and ice giants that could be mistaken for Earth-mass
planets, thereby reducing the time spent identifying false positives. Fourth,
mass measurements from RVs will provide the surface gravities necessary for
interpreting atmospheric spectra and potential biosignatures.
