View source for 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 
	
- Type:	Laboratory Experiment facility

[[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 


[[Photometry]] :	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
 	
[[Samples]] 
- 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 (bright & coarse grained samples) 			120 mm in diameter, 2-10 mm deep (dark or fine grained samples) 
			mini: 	25 mm x 120 mm (for principal plane observation down to 80°) 
				25 mm x 45 mm (for principal plane observation down to 60°) 
[[Temperature]]:	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 -> 2003 
				low temperature : tested in cold room down to -20°C 
[[
Availability to community]]: 	Technical improvements/calibration (20%) 
				LPG + associated laboratories measurements (60%) 
				open 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


* Characteristics: [[File:Spectro-Gonio_characteristics.pdf]]
* Article Brissaud et al. 2004: [[File:brissaud04-AplOpt-43-1926_spectrogonio-radiometer.pdf]]