ExEP Yield Modeling Tool and Validation Test Results

EXOSIMS is an open-source simulation tool for parametric modeling of the detection yield and characterization
of exoplanets. EXOSIMS has been adopted by the Exoplanet Exploration Programs Standards De nition and
Evaluation Team (ExSDET) as a common mechanism for comparison of exoplanet mission concept studies.
To ensure trustworthiness of the tool, we developed a validation test plan that leverages the Python-language
unit-test framework, utilizes integration tests for selected module interactions, and performs end-to-end cross-
validation with other yield tools. This paper presents the test methods and results, with the physics-based tests
such as photometry and integration time calculation treated in detail and the functional tests treated summarily.
The test case utilized a 4m unobscured telescope with an idealized coronagraph and an exoplanet population
from the IPAC radial velocity (RV) exoplanet catalog. The known RV planets were set at quadrature to allow
deterministic validation of the calculation of physical parameters, such as working angle, photon counts and
integration time. The observing keepout region was tested by generating plots and movies of the targets and the
keepout zone over a year. Although the keepout integration test required the interpretation of a user, the test
revealed problems in the L2 halo orbit and the parameterization of keepout applied to some solar system bodies,
which the development team was able to address. The validation testing of EXOSIMS was performed iteratively
with the developers of EXOSIMS and resulted in a more robust, stable, and trustworthy tool that the exoplanet
community can use to simulate exoplanet direct-detection missions from probe class, to WFIRST, up to large
mission concepts such as HabEx and LUVOIR.