Payload requirements for the Solar Probe

Abstract

The scientific goals and objectives for a Solar Probe determine the requirements for a model payload and concepts for the instruments. To accomplish the main aim, which is to make in-situ measurements of particles and fields in the solar corona and wind, the strawman payload must include a magnetometer and plasma wave instrument, fast three-dimensional plasma anlyzers to measure ions and electrons, and detectors for suprathermal and solar energetic particles. In addition a light-weight dust detector is required to probe the dust environment in the outer corona. Tight constraints are to be placed on all instruments concerning mass, power and telemetry in order to keep the expected costs and complexity to a bare minimum. This will require further developments of existing instruments or innovative concepts, allowing the objectives to be met with a payload of only 20 to 25 kg. All instruments have to be acommodated on a three-axis stabilized probe and should be capable of measuring particle fluxes that might vary by many orders of magnitude. The plasma experiments are central to the mission and very demanding because of the wide dynamic ranges required for the spatial, temporal, and particle-species energy, mass and charge state measurements. Furthermore, ion velocity distributions are expected to range from subsonic to supersonic in the Sun's frame of reference and are to be measured from a spacecraft with speed of about 300 km/s near perihelion at 4 R ⊙. Also shapes and heat flux tails of the distributions must be resolved, as they carry information crucial to the determination of coronal heating and solar wind acceleration mechanisms. The wave experiments must identify the wave modes and spectral intensities, which are essential for quantifying the wave effects on particles and their energization.