Arcsecond Space Telescope Enabling Research in Astrophysics

ASTERIA (Arcsecond Space Telescope Enabling Research in Astrophysics) was a technology demonstration and opportunistic science mission to conduct astrophysical measurements using a CubeSat. Originally envisioned as a project for training early career scientists and engineers, ASTERIA's technical goal was to achieve arcsecond-level line-of-sight pointing error and highly stable focal plane temperature control. These technologies are important for precision photometry, i.e., the measurement of stellar brightness over time. Precision photometry, in turn, provides a way to study stellar activity, transiting exoplanets, and other astrophysical phenomena.

ASTERIA was a 6U CubeSat (roughly 10 x 20 x 30 cm, 10 kg) that was operating in low-Earth orbit. The payload consisted of a lens and baffle assembly, a CMOS imager, and a two-axis piezoelectric positioning stage on which the focal plane is mounted. A set of commercial reaction wheels provided coarse attitude control. Fine pointing control was achieved by tracking a set of guide stars on the CMOS sensor and moving the piezoelectric stage to compensate for residual pointing errors. Precision thermal control was achieved by isolating the payload from the spacecraft bus, passively cooling the detector, and using trim heaters to perform small temperature corrections over the course of an observation.

Since completing its primary mission objectives, ASTERIA continued operating through four mission extensions until loss of contact in early December 2019. During these extensions, the spacecraft was used as an in-space platform to test various capabilities that aim to make CubeSats more autonomous, some of which are based on artificial intelligence programs. ASTERIA also made opportunistic observations of the Earth, a comet, other spacecraft in geo-synchronous orbit and stars that might host transiting exoplanets.