Science Parametrics for Missions to Search for Earthlike Exoplanets by Direct Imaging

Abstract

We use $N_t$, the number of exoplanets observed in time $t$, as a science metric to study direct-search missions like Terrestrial Planet Finder. In our model, $N$ has 27 parameters, divided into three categories: 2 astronomical, 7 instrumental, and 18 science-operational. For various "27-vectors" of those parameters chosen to explore parameter space, we compute design reference missions to estimate $N_t$. Our treatment includes the recovery of completeness $c$ after a search observation, for revisits, solar and antisolar avoidance, observational overhead, and follow-on spectroscopy. Our baseline 27-vector has aperture $D=16$m, inner working angle $IWA=0.039^{\prime \prime }$, mission time $t=0-5$ years, occurrence probability for earthlike exoplanets $\eta =0.2$, and typical values for the remaining 23 parameters. For the baseline case, a typical five-year design reference mission has an input catalog of $\sim$4700 stars with nonzero completeness, $\sim$1300 unique stars observed in $\sim$2600 observations, of which $\sim$1300 are revisits, and it produces $N_1\sim 50$ exoplanets after one year and $N_5\sim 130$ after five years. We explore offsets from the baseline for ten parameters. We find that $N$ depends strongly on $IWA$ and only weakly on $D$. It also depends only weakly on zodiacal light for $Z<50$ zodis, end-to-end efficiency for $h>0.2$, and scattered starlight for $\zeta <10^{-10}$. We find that observational overheads, completeness recovery and revisits, solar and antisolar avoidance, and follow-on spectroscopy are all important factors in estimating $N$.

37 pages, 11 figures, 11 tables; ApJ accepted version

References in corpus (1)

• New Completeness Methods for Estimating Exoplanet Discoveries by Direct Detection

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