Kiel sensors for the EPD instrument on-board Solar Orbiter - An overview of the qualification and acceptance test campaigns in phase D

Solar Orbiter is ESA's next solar and heliospheric mission which is planned to be launched in October 2018. The Energetic Particle Detector (EPD) on board on Solar Orbiter will provide key measurements for the Solar Orbiter science objectives. The EPD suite consists of four sensors; STEP, SIS, EPT and HET. The University of Kiel in Germany is responsible for the design, development, and building of STEP, and the two identical units EPT-HET 1 and EPT-HET 2. ESA's Solar Orbiter will explore the heliosphere at heliocentric distances between 0.28AU and 0.9AU and with inclination up to 38deg with respect to the Sun's equator. The spacecraft uses a heat shield to protect the bus and externally mounted instruments from the solar flux at the close distances to the sun. All three EPD-Kiel units are mounted externally but in different positions on the spacecraft outer deck. Although being protected by the spacecraft heat shield from high solar flux, EPT-HET1 and EPT-HET-2 as well as STEP experience a harsh environmental condition during the course of the mission. In addition due to the highly demanding science requirements, the qualification and acceptance test requirements of these externally mounted units are quite challenging. In this paper we present the development status of the EPT-HET 1, EPT-HET 2 and STEP sensors focusing on the activities performed in phase D and the qualification and acceptance test campaigns. The main objective of these test campaigns is to ensure and demonstrate the compatibility between the scientific requirements and the harsh environment expected during the mission. This paper includes the results summary of the environmental tests on the EPT-HET and STEP Proto-Qualification Models (PQMs) as well as Proto-Flight Models (PFMs). Only an adequate selection of environmental qualification and acceptance campaigns will guarantee the success of the scientific space missions.