The technique of transit spectroscopy has given us our first insights into the atmospheric features of exoplanets. The extremely low signals involved in detecting an atmosphere mean that such observations are vulnerable to noise and systematics, and that the estimation of the final uncertainties must be made as accurately as possible. Although a number of models have been produced to simulate such noise there is a paucity of numerical simulators that can capture complex time-domain effects. ExoSim is a novel, generic, numerical end-to-end simulator of transit spectroscopy intended as open-access software. It permits the simulation of a time-resolved spectroscopic observation in either primary transit or secondary eclipse. The observational parameters can be adjusted, and the telescope and instrument parameters changed in a simple manner to simulate a variety of existing or proposed instruments. ExoSim is a tool to explore a variety of signal and noise issues that occur in, and might bias, transit spectroscopy observations, including the effects of the instrument systematics, correlated noise sources, and stellar variability. The simulations are fast, which allows ExoSim to be used for Monte Carlo simulations of such observations. ExoSim is versatile and has been applied to existing instruments such as the Hubble Wide Field Camera 3, as well as planned instruments, where it is being used in the study phase of the proposed ARIEL exoplanet characterization mission. In this paper we present ExoSim, contrast it with other exoplanet simulators, give an overview of its structure, and review its range of applications.

Date Published: 29 July 2016
PDF: 9 pages
Proc. SPIE 9904, Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave, 99043R (29 July 2016); doi: 10.1117/12.2234216

Published in SPIE Proceedings Vol. 9904:
Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave
Howard A. MacEwen; Giovanni G. Fazio; Makenzie Lystrup; Natalie Batalha; Nicholas Siegler; Edward C. Tong, Editor(s)