Emissivity of Elgiloy and pure niobium at high temperature for the Solar Orbiter mission

The science payload of the Solar Orbiter mission that will be launched in 2018 comprises the RPW (Radio and Plasma Waves) experiment that will perform in situ and remote-sensing measurements (magnetic and electric fields). Some parts of this instrument will be made of Elgiloy for the antennas and must be protected from the intense solar radiation by a heat shield made in niobium. Emissivity of both materials is important to know in order to correctly model before launch the heat transfer in the instrumentation. Hemispherical emissivity results in the two following wavelength ranges 0.6–2.8 and 0.6–40 μm are presented at temperatures up to 1500 K for these two materials according to their surface roughness particularly for the niobium samples and at room temperature in the wavelength range 0.25–25 μm. New original data are obtained for both the materials at high temperature.