  Today, the near-Earth space is facing a paradigm change as the number of new
spacecraft is literally sky-rocketing. Increasing numbers of small satellites
threaten the sustainable use of space, as without removal, space debris will
eventually make certain critical orbits unusable. A central factor affecting
small spacecraft health and leading to debris is the radiation environment,
which is unpredictable due to an incomplete understanding of the near-Earth
radiation environment itself and its variability driven by the solar wind and
outer magnetosphere. This paper presents the FORESAIL-1 nanosatellite mission,
having two scientific and one technological objectives. The first scientific
objective is to measure the energy and flux of energetic particle loss to the
atmosphere with a representative energy and pitch angle resolution over a wide
range of magnetic local times. To pave the way to novel model - in situ data
comparisons, we also show preliminary results on precipitating electron fluxes
obtained with the new global hybrid-Vlasov simulation Vlasiator. The second
scientific objective of the FORESAIL-1 mission is to measure energetic neutral
atoms (ENAs) of solar origin. The solar ENA flux has the potential to
contribute importantly to the knowledge of solar eruption energy budget
estimations. The technological objective is to demonstrate a satellite
de-orbiting technology, and for the first time, make an orbit manoeuvre with a
propellantless nanosatellite. FORESAIL-1 will demonstrate the potential for
nanosatellites to make important scientific contributions as well as promote
the sustainable utilisation of space by using a cost-efficient de-orbiting
technology.

Space Physics