Spectro-Gonio Radiometer
Laboratory Experiment facility
spectro-gonio radiometer
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)
- 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
absolute:
- 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°)
- room temperature or heated
- down to -20°C (in cold room)
- down to -40°C (in SERAC environmental cell)
- PC/Windows, fully software controlled (LabView©). Automatic acquisition of all spectral/geometric configurations
- typical 15 mn for 200 spectral channels in visible (S/N dependent)
- total : 15 hours for 100 spectral channels and 100 geometries
- 0.3 - 5 µm range : fully calibrated
- polarization : tested (not available for external users)
- low temperature : tested in cold room down to -20°C
- Characteristics: File:Spectro-Gonio characteristics.pdf
- Article Brissaud et al. 2004: File:Brissaud04-AplOpt-43-1926 spectrogonio-radiometer.pdf
Availability to community:
- Technical improvements/calibration (20%)
- IPAG + associated laboratories measurements (60%)
- open as facility or to specific collaborations w. funding (20%)
References:
- 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.
- 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.
- Pommerol, A., and B. Schmitt 2008. 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 2008. 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].
- Pommerol, A., Schmitt B., Beck, P., Brissaud, O. 2009. Water sorption on Martian regolith analogs: thermodynamics and near-IR reflectance spectroscopy. Icarus soumis
