Spectro-Gonio Radiometer

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Laboratory Experiment facility

This spectro-gonio radiometer has been specially designed to measure with a high photometric accuracy the bidirectional reflectance of bright planetary materials over most of the solar spectrum and under wide illumination/observation configurations.

Location: Institut de Planétologie et Astrophysique de Grenoble CNRS - Université Grenoble Alpes Saint Martin d’Hères, France

Persons in charge:

- Scientific : Bernard Schmitt, Research director

- Technical : Olivier Brissaud, Engineer

Technical characteristics:

Spectral range : 0.3 - 4.5 µm (-> 5.0 µm: lower S/N) (4.2-4.3µm: atm. CO2 limited)

Spectral resolution : variable

- mini: < 0.1 nm (but S/N limited)

- maxi: 6 nm (<750nm), 12 nm (<1500nm), 24 nm (<3000nm), 48nm (>3000nm)

Bidirectional Reflectance

- Incidence angle: 0° to 85° ; resolution: 0.1° ; maximum sampling : 0.1°

- Emergence angle: 0° to 80° (to 83° for dark / fine grained samples) ; resolution : ± 2° (may be reduced to < ± 0.5°, but S/N limited) ; max. sampling : 0.1°

- Azimuth angle: 0° to 180° ; resolution : ± 2° (may be reduced to < ± 0.5°, but S/N limited) ; max. sampling : 0.1°

- Phase angle: mini to 165° ; mini : ~ 8° for bright / large grained samples ; ~ 4° for dark / fine grained samples

- Illumination diameter (nadir): 200 mm - Observation diameter (nadir): 20 mm



- 0.3-1.0 µm: better than 1% over all configurations (relative to a calibrated Spectralon 0.99 reference panel)

- 1.0-2.5 µm: better than 1% over all configurations

- 2.5-5 µm : better than 2% over all configurations

relative :

- better than 0.5% (0.3-2.5 µm)

Polarimetry options (only partly tested)

Illumination :

- linear polarization : variable 0 to 90° ; spectral range : 0.3 - 2.8 µm

Observation :

- 1 component over the 0.3 - 5µm range + unpolarized or || and ┴ components over restricted spectral range


- Types: rocks, minerals, snow / ice, sulfur, ... (from very bright to dark)

- Texture: compact or granular

- Grain size: micrometer to a few millimeters

- Size;

maxi: 300mm diameter, 250 mm deep (for bright & coarse grained samples) OR 120 mm in diameter, 2-10 mm deep (for dark or fine grained samples)

mini: 25 mm x 120 mm (for principal plane observation down to 80°) OR 25 mm x 45 mm (for principal plane observation down to 60°)

Spectro-Gonio 30-45deg.jpg

Picture: General view of the Spectro-gonio radiometer at IPAG


Picture: General view of the instrumentation


- room temperature or heated

- down to -20°C (in cold room)

- down to -40°C (in SERAC environmental cell)

Experiment control:

- PC/Windows, fully software controlled (LabView©). Automatic acquisition of all spectral/geometric configurations

Acquisition time:

- typical 15 mn for 200 spectral channels in visible (S/N dependent)

- total : 15 hours for 100 spectral channels and 100 geometries

Current state of system:

- 0.3 - 5 µm range : fully calibrated

- polarization : tested (not available for external users)

- low temperature : tested in cold room down to -20°C

Availability to community:

- Technical improvements/calibration (20%)

- IPAG + associated laboratories measurements (60%)

- open as facility or to specific collaborations w. funding (20%)


- Bonnefoy, N., O. Brissaud, B. Schmitt, S. Douté, M. Fily, W. Grundy, and P. Rabou 2000. Experimental system for the study of planetary surface materials’ BRDF. Remote Sensing. Rev., 19, 59-74 [doi: 10.1080/02757250009532410].

- Bonnefoy, N. 2001. Développement d’un spectrophoto-goniomètre pour l’étude de la réflectance bidirectionnelle des surfaces géophysiques. Application au soufre et perspectives pour le satellite Io. PhD Thesis, LPG - Université Joseph Fourier, Grenoble (20/11/2001).

- Brissaud, O., B. Schmitt, N. Bonnefoy, S. Douté, P. Rabou, W. Grundy, and M. Fily 2004. Spectrogonio radiometer for the study of the bidirectional reflectance and polarization functions of planetary surfaces: I. Design and tests. Appl. Optics, 43 (9), 1926-1937 [doi: 10.1364/AO.43.001926].

- Bernard, J-M, E. Quirico, O. Brissaud, G. Montagnac, , B. Reynard, P. Mc Millan, P. Coll, M-J Nguyen, F. Raulin, B. Schmitt 2006. Reflectance spectra and chemical structure of Titan’s tholins. Application to the analysis of CASSINI-HUYGENS observations. Icarus 185, 301-307 [doi: 10.1006/icar.2001.6726].

- Pommerol, A., and B. Schmitt 2008a. Strength of the H2O near-infrared absorption bands in hydrated minerals: Effects of particle size and correlation with albedo. J. Geophys. Res E, 113, E10009 [doi:10.1029/2007JE003069]

- Pommerol, A., and B. Schmitt 2008b. Strength of the H2O near-infrared absorption bands in hydrated minerals: Effects of measurement geometry. J. Geophys. Res E, 113, E12008 [doi: 10.1029/2008JE003197].

- Quirico, E., G. Montagnac, V. Lees, P. F. McMillan, C. Szopa, G. Cernogora, J-N Rouzaud, P. Simon, J-M Bernard, P. Coll, N. Fray, B. Minard, F. Raulin, B. Reynard, B. Schmitt 2008. New experimental constraints on the composition and structure of tholins. Icarus, 198, 218-231 [doi: 10.1016/j.icarus.2008.07.012].

- Pommerol, A., B. Schmitt, P. Beck, and O. Brissaud 2009. Water sorption on Martian regolith analogs: thermodynamics and near-infrared reflectance spectroscopy. Icarus, 204, 114-136 [doi: 10.1016/j.icarus.2009.06.013].

- Pommerol A. 2009. Hydratation minérale à la surface de mars : Caractérisation spectroscopique, thermodynamique et application a la télédétection. PhD Dissertation, Université Joseph Fourier, Grenoble.

- Dumont, M., O. Brissaud, G. Picard, B. Schmitt, J.C.Gallet, and Y. Arnaud, 2010. High-accuracy measurements of snow Bidirectional Reflectance Distribution Function at visible and NIR wavelengths; comparison with modelling results. Atm. Chem. Phys 10, 2507-2520. [doi: ?] (Atm. Chem. Phys. Discuss. 2009, 9, 19279-1933).

- Beck, P., A. Pommerol, B. Schmitt and O. Brissaud 2010. Kinetics of water adsorption on minerals and the breathing of the Martian regolith. J. Geophys. Res. E. 115, E10011 [doi: 10.1029/2009JE003539].

- Beck, P., E. Quirico, D. Sevestre, G. Montes-Hernandez, A. Pommerol, B. Schmitt, J-A Barrat, and P. Gillet 2011. Goethite as an alternative origin for the 3.1 µm band on dark asteroids. Astron. Astrophys., 526, A85 (correction: AA 530, C2) [doi: 10.1051/0004-6361/201015851e].

- Beck, P., J-A. Barrat, F. Grisolle, E. Quirico, B. Schmitt, F. Moynier, P. Gillet, and C. Beck 2011. NIR spectral trends of HED meteorites: Can we discriminate between the magmatic evolution, mechanical mixing and observation geometry effects? Icarus, 216, 560-571 [doi: 10.1016/j.icarus.2011.09.015].

- Grisolle F. 2013. Les condensats saisonniers de Mars : étude expérimentale de la formation et du métamorphisme de glaces de CO2. PhD Dissertation, Université Joseph Fourier, Grenoble.

- Massé, M., P. Beck, B. Schmitt, A. Pommerol, A. McEwen, V.F. Chevrier, O. Brissaud and A. Séjourné 2014. Spectroscopy and detectability of liquid brines on Mars. Planetary & Space Sciences, 92, 136-149 [doi: 10.1016/j.pss.2014.01.018].

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