AZ-2000-IECW and StaMet Black Kapton Options for Solar Probe Plus MAG Sensor MLI Kevlar/Polyimide Shells

The Magnetometer (MAG) is a unit of the FIELDS instrument on the Solar Probe Plus (SPP). It includes an inboard unit and an outboard unit, which are mounted to a deployable boom. The sensors are insulated with multilayer insulation (MLI). Sunlight, with solar irradiance equivalent to two Suns, is incident on the MLIs at a 45° angle during downlink at 0.7 AU. If the MLI outer cover is specular, it leads to straylight glint to the star trackers. Also, conductive coatings are required for the SPP mission. Therefore, a coating for the sensor MLI is required to meet the straylight, ESD and sensor temperature requirements. Additionally, the MLIs and harness need protection from solar dust and micrometeoroids. All the MLI film materials commercially available have high solar specularity. Black Kapton has a high solar absorptance. When exposed to 2 suns, its temperature will be 200°C. Also, its solar specularity is high. The innovation in this paper applies the commercially available AZ-2000-IECW white paint to a commercially available black Kapton/Kevlar/Kapton laminate to make a flexible, bendable and light-weight solar diffuser shell for MLIs. The MLP-300-AZ epoxy primer, with oxygen plasma treatment, enhances its adhesion. The shell is 0.2 mm thick, flexible, bendable and light-weight. AZ-2000-IECW white paint is conductive and meets the SPP mission ESD requirement. Its low absorptance (0.26 at beginning of life; 0.45 (conservative) at end of life) and high emittance (0.89) keeps the MLI adequately cool even if it is exposed to two suns. The innovation in this paper is not bright in sunlight. It resolves the straylight glint issue for the star trackers. It can also be used to minimize sunlight or straylight glint to cameras or star trackers for other missions. Flight qualification testing of this innovation has been completed at GSFC and will be presented.