THIS XRP WILL USE RADIAL VELOCITIES FROM APPROVED AND ARCHIVAL PROGRAMS AT NASA/KECK'S KPF AND NN-EXPLORE'S WIYN/NEID TO MEASURE MASSES OF OVER 40 SUB-NEPTUNES, AS WELL AS RE-ANALYZING ARCHIVAL TESS, K2, AND KEPLER TO MEASURE PRECISE PLANET SIZES (VIA TRANSITS) AND, WHERE POSSIBLE, STELLAR PROPERTIES (VIA ASTEROSEISMOLOGY). OUR RESEARCH PROGRAM WILL EMPIRICALLY TEST THE WATER WORLD HYPOTHESIS, AND MAXIMIZES THE SCIENTIFIC RETURN OF TESS, K2, AND KEPLER AND ENSURES THAT HIGH-PRIORITY TARGETS FOR JWST AND ARIEL ARE IDENTIFIED AND ACCURATELY CHARACTERIZED. IN ADDITION, OUR PROGRAM WILL KEEP TARGETS FLOWING IN SUPPORT OF JWST (AND FUTURE ARIEL) ATMOSPHERIC SPECTROSCOPY, AND ALONG THE WAY IT WILL ALSO QUANTIFY STELLAR ACTIVITY IN PLANET-HOSTING SYSTEMS ACROSS A RANGE OF STELLAR TYPES THAT CLOSELY TRACKS THE HWO TARGET DISTRIBUTION, MEASURE SYSTEM ARCHITECTURES, AND CONSTRAIN INTERIOR COMPOSITIONS OF PLANETS STRADDLING THE SUPER-EARTH/SUB-NEPTUNE BOUNDARY.