A critical review of the heliospheric in situ instrumentation planned for the solar orbiter

This paper provides a very brief review of the in situ instrument payload initially planned for the European Space Agency's Solar Orbiter space mission, as documented in the Solar Orbiter Study Report. That proposed payload comprises eight experiments including a solar wind electron and ion plasma analyzer (including composition), a radio and plasma wave analyzer, a radio sounder, a magnetometer, an energetic particle analyzer, a dust detector, a neutral solar wind analyzer, and a neutron detector. Only 25.2 kg and 23.5 We have been initially allocated to the in situ instruments; these resources are probably insufficient to fully support this diverse and challenging set of experiments. Once it is better developed and optimized, the in situ package will provide an excellent and central component of the Solar Orbiter science return. While not exhaustive, this paper seeks to identify and provide some guidance on at least some of the issues facing each of the in situ experiments.