Get the heat on – Obtaining high temperature emissivity measurements in support of the analysis of surface data from VIRTIS on VenusExpress

Kurzfassung

Analyzing the surface composition of Venus from remote-sensing measurements is a challenging task. Recently we have reported on brightness variations in the near infrared wavelength range observed with VIRTIS on VenusExpress. Our implication is that these brightness variations might be correlated to emissivity variations of the surface material. The next step to verify this hypothesis is to obtain data in the relevant spectral range at temperatures typical for the surface of Venus. We are currently developing a Planetary Emissivity Laboratory (PEL) at Deutsches Zentrum für Luft- und Rahmfahrt (DLR) in Berlin. The PEL allows measuring the emissivity of planetary analog materials grain sizes fractions from less than 25 microns all the way to bulk samples and at temperatures of more than 400°C, typically for the surface of Venus. The PEL development follows a multi-step approach. We are currently installing a new calibration target that will allow obtaining emissivity data on the full range from 1 to 50 microns with a usable signal-to-noise ratio. Here we will present first data in the range from 1 to 1.4 microns which covers the atmospheric windows used for the surface observations from VIRTIS on VenusExpress. We will focus especially on which measurements are necessary to verify our earlier hypotheses of compositional variations on the surface of Venus.