  Next-generation space observatories will conduct the first systematic surveys
of terrestrial exoplanet atmospheres and search for evidence of life beyond
Earth. While in-depth observations of the nearest habitable worlds may yield
enticing results, there are fundamental questions about planetary habitability
and evolution which can only be answered through population-level studies of
dozens to hundreds of terrestrial planets. To determine the requirements for
next-generation observatories to address these questions, we have developed
Bioverse. Bioverse combines existing knowledge of exoplanet statistics with a
survey simulation and hypothesis testing framework to determine whether
proposed space-based direct imaging and transit spectroscopy surveys will be
capable of detecting various hypothetical statistical relationships between the
properties of terrestrial exoplanets. Following a description of the code, we
apply Bioverse to determine whether an ambitious direct imaging or transit
survey would be able to determine the extent of the circumstellar habitable
zone and study the evolution of Earth-like planets. Given recent evidence that
Earth-sized habitable zone planets are likely much rarer than previously
believed (Pascucci et al. 2019), we find that space missions with large search
volumes will be necessary to study the population of terrestrial and habitable
worlds. Moving forward, Bioverse provides a methodology for performing trade
studies of future observatory concepts to maximize their ability to address
population-level questions, including and beyond the specific examples explored
here.
