Solar orbiter neutral solar-wind detector

Neutral hydrogen atoms, which give rise to the prominent solar Ly-? corona, are closely coupled to the emerging solar-wind plasma. The density ratio of neutral hydrogen to protons is minute, ?10-6; therefore, the neutral atoms are tracers in the solar wind. In-situ observations of the neutral atoms, their flight paths (imaging), density, and velocity distributions are a new tool to the understanding of the Ly-? corona, i.e. setting limits on the plasma velocity distribution along the solar magnetic field lines. The other goal of the neutral solar-wind instrumentation is the in-situ observation of the interactions between solar wind plasma and dust grains near the Sun. We will discuss the science objectives and the potential "zero charge" solar-wind instrument envelope onboard Solar Orbiter.