Roughly 40 billion M dwarfs in our galaxy host at least one small planet in the habitable zone (HZ). The stellar ultraviolet (UV) radiation from M dwarfs is strong and highly variable, and impacts planetary atmospheric loss, composition and habitability. These effects are amplified by the extreme proximity of their HZs (0.1–0.4 AU). Knowing the UV environments of M dwarf planets will be crucial to understanding their atmospheric composition and a key parameter in discriminating between biological and abiotic sources for observed biosignatures. The Star-Planet Activity Research CubeSat (SPARCS) will be a 6U CubeSat devoted to photometric monitoring of M stars in the far-UV and near-UV, measuring the time-dependent spectral slope, intensity and evolution of low-mass star high-energy radiation.
ACCESS (Actively-Corrected Coronagraph for Exoplanet System Studies) was one of four medium-class exoplanet
concepts selected for the NASA Astrophysics Strategic Mission Concept Study (ASMCS) program in 2008/2009 [14,
15]. The ACCESS study evaluated four major coronagraph concepts under a common space observatory. This paper
describes the high precision pointing control system (PCS) baselined for this observatory.
ACCESS is one of four medium-class mission concepts selected for study in 2008-9 by NASA's Astrophysics Strategic
Mission Concepts Study program. ACCESS evaluates a space observatory designed for extreme high-contrast imaging
and spectroscopy of exoplanetary systems. An actively-corrected coronagraph is used to suppress the glare of diffracted
and scattered starlight to contrast levels required for exoplanet imaging. The ACCESS study considered the relative
merits and readiness of four major coronagraph types, and modeled their performance with a NASA medium-class space
telescope. The ACCESS study asks: What is the most capable medium-class coronagraphic mission that is possible with
telescope, instrument, and spacecraft technologies available today? Using demonstrated high-TRL technologies, the
ACCESS science program surveys the nearest 120+ AFGK stars for exoplanet systems, and surveys the majority of
those for exozodiacal dust to the level of 1 zodi at 3 AU. Coronagraph technology developments in the coming year are
expected to further enhance the science reach of the ACCESS mission concept.
Over the last two years, we have studied system concepts for the International X-ray Observatory (IXO) with the goal of
increasing the science return of the mission and to reduce technical and cost risk. We have developed an optical bench
concept that has the potential to increase the focal length from 20 to 25 m within the current mass and stability
requirements. Our deployable bench is a tensegrity structure formed by two telescoping booms (compression) and a
hexapod cable (tension) truss. This arrangement achieves the required stiffness for the optical bench at minimal mass
while employing only high TRL components and flight proven elements. The concept is based on existing elements, can
be fully tested on the ground and does not require new technology.
Our design further features hinged, articulating solar panels, an optical bench fully enclosed in MLI and an instrument
module with radially facing radiator panels. We find that our design can be used over a wide range of sun angles, thereby
greatly increasing IXO's field of regard, without distorting the optical bench. This makes a much larger fraction of the
sky instantaneously accessible to IXO.