The ExoplanetSat Mission to Detect Transiting Exoplanets with a CubeSat Space Telescope

We present a CubeSat mission for the discovery of exoplanets down to 1 Earth radius around the nearest and brightest Sun-like stars. The spacecraft prototype―termed ExoplanetSat―is a 3U space telescope designed to monitor a single target from low Earth orbit. The optical payload will precisely measure stellar brightness, seeking the characteristic dip in intensity that indicates a transiting exoplanet. Once ExoplanetSat identifies a candidate exoplanet, larger assets can be used to conduct follow-up observations to characterize the atmospheric constituents. The prototype will serve as the basis of an eventual fleet of nanosatellites, each independently monitoring a single bright, nearby star. Given the spacecraft’s low mass and sub-pixel sensitivity variations in the science detector, image jitter and its resultant photometric noise is a primary concern. The attitude determination and control subsystem (ADCS) mitigates this using a two-stage pointing control architecture that combines 3-axis reaction wheels for arcminute-level coarse pointing with a piezoelectric translation stage at the focal plane for fine image stabilization to the arcsecond level. The ExoplanetSat optical design combines star camera and science functions into a single device that fits into the 3U form factor. This paper presents the ExoplanetSat science case, mission overview, concept of operations, and spacecraft configuration