Thermal Design of the Solar Orbiter SPICE instrument

The European Space Agency Solar Orbiter spacecraft is planned for launch in July 2017. It is targeted for an elliptical orbit about the Sun, with a minimum perihelion of 0.284 Astronomical Units (AU). The thermal challenge is therefore management of the extreme (~17 kW/m2) solar heat input at perihelion. Solar Orbiter is designed to identify the origins and causes of the solar wind, the heliospheric magnetic field, solar energetic particles, the transient interplanetary disturbances, and the Sun's magnetic field itself. The Spectral Imaging of the Coronal Environment (SPICE) instrument is one of six remote sensing instruments on the spacecraft. It is a high resolution imaging spectrometer operating at ultraviolet wavelengths. The driving requirement for the SPICE thermal design is to manage the solar load incident through the aperture in the spacecraft heat-shield. At a perihelion this solar load is 44 W. However, the thermal control system must also be compliant during periods with little or no solar loading and with the conditions during the Earth and Venus gravity assist maneuvers required for orbit adjustment. A key feature of the thermal design is a selectively transparent primary mirror that reflects the science beam but allows much of the solar energy to be transmitted and then reflected to space. Currently we are in the detailed definition phase (C) of the project. This paper describes the design and analysis that has been undertaken to define the thermal control system.