In 2021, the NASA-funded Star-Planet Activity Research CubeSat (SPARCS) spacecraft will carry a small telescope into Earth orbit on a mission to monitor the flares and sunspots of small stars to assess how habitable the space environment is for planets orbiting them. The mission, including spacecraft design, integration and resulting science, is led by Arizona State University's School of Earth and Space Exploration (SESE). "This is a mission to the borderland of astrophysics and astrobiology," said Evgenya Shkolnik, assistant professor in SESE and principal investigator for the SPARCS mission. "We're going to study the habitability and high-energy environment around stars that we call M dwarfs." The stars that SPARCS will focus on are small, dim and cool by comparison to the sun. Having less than half the sun's size and temperature, they shine with barely one percent its brightness. Astronomers have discovered that essentially every M dwarf star has at least one planet orbiting it, and about one system in four has a rocky planet located in the star's habitable zone. This is the potentially life-friendly region where temperatures are neither too hot nor too cold for life as we know it, and liquid water could exist on the planet's surface. Because M dwarfs are so plentiful, astronomers estimate that our galaxy alone contains roughly 40 billion rocky planets in habitable zones around their stars. Most of the habitable-zone planets in our galaxy orbit M dwarfs. The nearest one, Proxima b, lies just 4.2 light-years away. M dwarf stars figure large in the exploration of exoplanets that dwell in other stars’ habitable zones. According to Shkolnik, while M dwarf stars are small and cool, they are more active than the sun, with flares and other outbursts that shoot powerful radiation into space around them. But no one knows exactly how active these small stars are. Over its one-year nominal mission, SPARCS will stare at target stars for weeks at a time in hopes of solving the puzzle. At the heart of the SPARCS spacecraft will be a telescope with a diameter of 3.6 in. plus a camera with two UV-sensitive detectors to be developed by NASA's Jet Propulsion Laboratory. Both the telescope and camera will be optimized for observations using UV light, which strongly affects the planet's atmosphere and its potential to harbor life on the surface. The spacecraft will contain three major systems — the telescope, the camera and the operational and science software. Along with Shkolnik, SESE astronomers Paul Scowen, Daniel Jacobs and Judd Bowman will oversee the development of the telescope and camera, plus the software and the systems engineering to pull it all together. The telescope uses a mirror system with coatings optimized for UV light. Together with the camera, the system can measure very small changes in the brightness of M dwarf stars to carry out the primary science of the mission. The instrument will be tested and calibrated at ASU in preparation for flight before being integrated into the rest of the spacecraft. "We'll have limited radio communications with SPARCS, so we plan to do quite a bit of data processing on board using the central computer," said Jacobs. "We'll be writing that software here at ASU, using a prototype of the spacecraft and camera to test our code." After launch, Jacobs said the team will do science operations at ASU, connecting up to SPARCS via a global ground station network. A key part of the mission plan, Shkolnik said, is to involve graduate and undergraduate students in various roles to give them with educational and training opportunities to become future engineers, scientists, and mission leaders. "The fast pace for development — from lab to launch might be as short as a couple of years – works well with student timescales," Shkolnik said. "They can work on it, start to finish, in the time they're here at ASU." Joining ASU in the SPARCS mission are scientists from the University of Washington, the University of Arizona, Lowell Observatory, the SouthWest Research Institute and NASA's Jet Propulsion Laboratory. "The SPARCS mission will show how, with the right technology, small space telescopes can answer big science questions," Shkolnik said. "How likely is it that we humans are alone in the universe? Where should we look for habitable planets? And can we find a new and more fruitful understanding of what makes an exoplanet system habitable?"