Current configuration of PEL
PEL is building on more than 20 years of experience in laboratory infrared spectroscopy in the institute. PEL allows obtaining spectral measurements of analog materials in emission, reflectance and transmission from the visible to the far infrared spectral range (0.4-100μm) under vacuum and purged air conditions. PEL has the unique capability to obtain emissivity measurement of planetary analog samples at temperature up to 1000K. This allows measuring samples at realistic temperature conditions for the surface of Mercury and Venus and to study the change in spectral characteristics induced by the high temperatures. Beside planetary applications this capability is also of interested for industrial customer testing 3D printing materials as well as high temperature coatings. PEL is currently equipped with two Fourier transform spectrometers, an evacuable Bruker Vertex 80V and a purged air Bruker IFS 88, both connected to planetary simulation chambers.
Test of the MERTIS instrument in PEL
The Bruker VERTEX 80V spectrometer is coupled to the high temperature planetary simulation chamber. The induction heating system installed in the chamber heats the samples to temperatures of up to 1000K. The chamber can be evacuated so that the full optical path from the sample to the detector is free of any influence by atmospheric gases. The chamber has an automatic sample transport system that allows maintaining the vacuum while changing the samples. To cover the 1-100 μm spectral range a “sandwich” liquid nitrogen-cooled MCT+InSb detector is used in combination with a wide range KBr beamsplitter from 1-16 µm and a DTGS (16 - 100 μm) detector with a KBr and Mylar Multilayer beam splitters for the remaining spectral range.
The older Bruker IFS 88 has an attached emissivity chamber, build at DLR. The chamber is purged with dry air to remove particulates, water vapor and CO2; its temperature can be set and maintained constant, typically at 10° or 20° C, but if needed it can be set to below zero. A heater in the chamber is used to heat samples to temperatures from 20° up to 180° C (adequate for Martian studies).
For supporting measurements both instruments are equipped with reflectance units. The VERTEX 80V can measure bi-directional reflectance of minerals, while the IFS 88 can measure the bi-conical reflectance. In addition the VERTEX 80V can measure the transmission of samples (incl. filter material) in the 1-100 μm range.