Small satellites have become a very versatile and widely used platform in the space sector. Especially, the number of CubeSats – a class of miniaturized satellites often used for educational purposes and for small science instruments and technology demonstrators – launched into low-Earth-orbits has risen significantly in recent years. CubeSat launch costs are low (typically 100 k€/unit or less) and lead times are expected to significantly drop from presently two or three years. Their small form factor imposes strict limits on size (one CubeSat unit has 10 cm side length) and mass (1.33 kg per unit) of instruments and on available power. Additionally, only small data volumes can be transmitted owing to scarce communication with ground stations (about one contact of a few minutes length per orbit). However, CubeSats are an excellent platform for miniature scientific instruments used in exploratory missions and for technology demonstrators and may be enhanced to self-contained science missions. They allow for university groups to enhance their expertise in innovative instrumentation and mission designs. The development times and cost scales allow student training in nearly all aspects of a space mission through active participation. Both education and technology verification can help to build future large-scale missions.
X-ray astronomy requires space missions. TRISTAN/TFH is a new Compton-polarimeter, embedded into a CubeSat, in continuity of the COCOTE-TRISTAN/TJB balloon flight pilot experiment, which flew in France in summer 2015. This polarimeter will continuously monitor Cygnus X-1 measuring the flux and polarization in the 100 keV range. This CubeSat project will include a novel TRISTAN type silicon drift detector matrix, sensitive for X-rays and developed at MPG/HLL, as well as CNRS scintillating detectors. It thus serves two purposes: being a technology demonstrator as well as collecting scientific data. A long-term observation of X-ray emission from Cygnus X-1 would allow to better understand mass accretion of the black hole. The project is a collaboration between TUM, MPP, and CEA and ORIGINS scientists have developed the TRISTAN detector-concept to search for sterile neutrinos within RU-B.