UC Riverside

The unprecedented contrast ratio of future direct imaging (DI) instruments offers a new pathway to discover and characterize exoplanets around nearby stars. The Nancy Grace Roman Space Telescope, set for launch before May 2027, will conduct a science demonstration mission with its coronagraph instrument to test the new technologies for high-contrast direct imaging of exoplanets. This mission serves as a stepping stone to the Habitable Worlds Observatory, which aims to directly image and characterize Earth-like planets in the habitable zones of nearby stars in the 2040s. To ensure the success of these highly anticipated missions, extensive precursor science is required. This dissertation addresses critical questions for the DI community and demonstrates the role of the radial velocity (RV) method in supporting these goals. I will showcase the RV method as not only a primary discovery tool but also as a unique means to reveal hidden details about planetary systems that other methods cannot access. Then, I will present a method that synergizes RV and DI and explores the parameter space within which planetary signatures are hidden in the RV signal noise due to precision limit but could be detected by DI. The information returned by complementing DI with RV will be crucial to an effective DI target selection process. Next, I will present two planetary discoveries along with a full characterization of a nearby system harnessing the full of power the RV. The result of which provides additional valuable candidates to the DI community. Lastly, I will investigate how observational factors influence the refinement of orbital periods of long-period planets and offer strategies for efficient ground-based RV precursor observations to the DI candidates. These strategies are designed to maximize reductions in planetary orbital location uncertainty using RV within limited time frames, such that DI candidates can be observed at the optimal epochs. The results contained within this dissertation provides key insights and guidelines for precursor science to maximize the science return of future DI missions.