Planetary Emissivity Laboratory (PEL)

 

Facility name:	Planetary Emissivity Laboratory (PEL)
Location:	Institute of Planetary Research DLR – German Aerospace Center Rutherfordstrasse 2, 12489 Berlin, Germany
Persons in charge:	Scientific : Jörn Helbert, Research director & Alessandro Maturilli, Laboratory Manager Technical : Ines Büttner, Sample preparation facility

General description

The Planetary Emissivity Laboratory (PEL) is a special sub-session of the Planetary Spectroscopy Laboratory (PSL)of the DLR in Berlin, devoted to emissivity measurements in of samples from low/moderate to high temperature (temperature range from 300 to above 1000 Kelvin).

Emissivity measurements are recorded by using an external emissivity chamber (DLR-custom-designed) attached to a Bruker Vertex80V FTIR from the visible to the far-IR (from 0.4 to 150 µm), with a high SNR. Induction system is used to heat up stainless steel cups containing the sample.
This system allows heating-up the samples to very high temperatures without having a heater in the chamber, also avoiding the contribution of emissivity chamber elements surrounding the sample cup to the measured target radiation.
A quartz carousel, with 12 positions for sample cups or reference materials in mounted in the chamber on a computer-controlled stepped motor. This allows measuring several targets per day without breaking the vacuum. The benefits of this procedure are twofold. From one side, it maximizes the number of samples measured per day, reducing the time interval between successive measurements, from the other side prevent the chamber to heat-up and contribute to the measured radiation.
The thermal radiation emitted normal to the surface by the sample is collected by an Au-coated parabolic off-axis mirror and reflected to the entrance port of the spectrometer. A copper cooler is mounted in the back of the parabolic mirror to cool it down and stabilize its reflecting characteristics.

12 thermopile temperature sensors (whose head is a long, thin wire of 0.2 mm) are available in the chamber to read the sample surface temperature.
A webcam is installed in the emissivity chamber to continuously monitor the sample behavior while heating.
Several USB ports are available in the external emissivity chamber to connect other monitoring devices.
A vacuum-tight window is carved on the upper lid of the emissivity chamber. By removing and replacing it with a VIS or IR filter the sample cup (after removal of the parabolic mirror) can be observed by any external measuring device, e.g. for IR imaging of the sample to monitor temperature distribution in the sample.
Between the emissivity chamber and the spectrometer there is a vacuum-tight separation mechanism, operated mechanically (uses compressed air). It is used to separate the two devices and it is kept closed while heating, opened just short before measurements, to prevent possible outgassing to contaminate the spectrometer.
A vacuum-tight optical window can be mounted in front of the emissivity chamber aperture to the spectrometer, in case measurements under inert gas atmosphere are foreseen.
The instrument is located in an air-conditioned room. The instruments and the accessory units used are fully automatized and the data calibration and reduction are made with homemade software.

Tools and sub-systems:

A number of sample preparation and analysis tools and experiment sub-systems are available to the facility:

For samples preparation: a collection of hundreds of rocks and minerals, synthetic minerals, an Apollo 16 lunar sample, several meteorites, set of sample holders for reflectance (plastic, aluminum or stainless steel), various sets of sieves, grinders, mortars, saw, balances, microscope, an oven (20° to 300°C), ultra-pure water, wet chemistry materials, a second ovens (30° to 3000°C) for sample treatments, a press to produce pellets (10mm or 20mm diameter), a large dry cabinet (moisture < 1%) for sample storage, 3 small exsiccators (moisture < 20%) for sample storage, a rotating device for producing intimate mixtures, purge gas generator for water and CO2 free air, liquid-nitrogen tank, an ultrasonic cleaning unit, 2 microscopes, air compressor pistol for cleaning.

Currently an In-Xitu’s Terra portable X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF) instrument is available at PEL for sample characterization.
 

Technical characteristics:

Spectral range:	1.0 - 150 µm (with high S/N, in vacuum, purged air or inert gas atmosphere)
Atmospheric pressure:	0.7 – 1000 mbar
Spectral resolution:	variable - mini: 0.1 cm-1 - maxi: 8 cm-1
Emissivity:	Emergence angle: 0°, 5°, 10 to 60° ; step 10° Sample holder diameter: 50 mm Sample thickness: 1 to 3 mm (can be larger for slabs or solid samples, to 10mm) Sample weight: to fill a cup, depending on the grain size, 3 to 5 grams of material are needed Cup rim height: 0mm or 20mm or 50mm, depending on the experiment and the need to minimize thermal gradients in the samples heated in vacuum
Samples:	Types: rocks, minerals (natural and synthetic), metals, ceramics, paints, blankets Texture: compact or granular Grain size: typical <25 µm, 25-63 µm, 63-125 µm, 125-250 µm + larger + slabs
Temperature:	From 300 to above 1000 Kelvin sample surface temperature
Experiment control:	PC/Windows, fully software controlled. Automatic acquisition of all spectral/geometric configurations
Acquisition time:	Depending on the number of consecutive scans on the same target Typical:5 to 7 min for 500 scans in VIS and TIR under one geometrical configuration

 

 Availability to community:

• Technical improvements/calibration (20%)
• DLR + associated laboratories measurements (60%)
• open as facility or to specific collaborations w. funding (20%)

 

To apply for time in this laboratory under the EuroPlanet Research Infrastructure please go to "Europlanet 2020 Research Infrastructure (RI): How to Apply for a TA visit?".

References:

Maturilli A, Helbert J, Witzke A, Moroz L (2006) Emissivity measurements of analogue materials for the interpretation of data from PFS on Mars Express and MERTIS on Bepi-Colombo. PSS 54(11):1057-1064

Maturilli A, Helbert J, Moroz L (2008) The Berlin emissivity database (BED). PSS 56(3-4):420-425

Helbert J, Maturilli A (2009) The emissivity of a fine-grained labradorite sample at typical Mercury dayside temperatures. EPSL 285(3–4):347–354, DOI: 10.1016/j.epsl.2009.02.031.

Sprague AL, Donaldson Hanna KL, Kozlowski RWH, Helbert J, Maturilli A, Warell JB, Hora JL (2009) Spectral emissivity measurements of Mercury's surface indicate Mg- and Ca-rich mineralogy, K-spar, Na-rich plagioclase, rutile, with possible perovskite, and garnet. PSS 57(3):364-383

Helbert J, Hiesinger H, Walter I, Sauberlich T, Maturilli A, D'Amore M, Knollenberg J, Lorenz E, Peter G, Arnold G (2010) MERTIS: understanding Mercury's surface composition from mid-infrared spectroscopy. Proc. SPIE 7808, 78080J, DOI:10.1117/12.859816

Vernazza P, Carry B, Emery J, Hora JL, Cruikshank H, Binzel RP, Jackson J, Helbert J, Maturilli A (2010) Mid-infrared spectral variability for compositionally similar asteroids: Implications for asteroid particle size distributions. Icarus 207(2):800-809

Helbert J, Maturilli A, D’Amore M (2013a) Visible and near-infrared reflectance spectra of thermally processed synthetic sulfides as a potential analog for the hollow forming materials on Mercury. EPSL 369-370:233-238, doi:10.1016/j.epsl.2013.03.045

Helbert  J, Nestola F, Ferrari S, Maturilli A, et al. (2013b) Olivine thermal emissivity under extreme temperature ranges: Implication for Mercury surface. EPSL 371:252–257, doi: 10.1016/j.epsl.2013.03.038.

Maturilli A, Helbert J (2014) Characterization, testing, calibration, and validation of the Berlin emissivity database. Journal of Applied Remote Sensing. doi:10.1117/1.JRS.8.084985

Maturilli A, Helbert J, St. John JM, Head III JW, Vaughan WM, D’Amore M, Gottschalk M, Ferrari S (2014) Komatiites as Mercury surface analogues: Spectral measurements at PEL. EPSL 398:58-65. doi:10.1016/j.epsl.2014.04.035