==== SHADOWS Micro Spectro-Gonio Radiometer ====
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=== Laboratory Experiment facility ===

**Facility name:** 

Micro Spectro-Gonio Radiometer

**Location:**
Institut de Planétologie et Astrophysique de Grenoble (IPAG)
 
CNRS - Université Grenoble Alpes 

Saint Martin d’Hères, France 

**Persons in charge:**
 
- Scientific : 		Pierre Beck,  Assistant Professor  & Bernard Schmitt, Research director
 
- Technical : 		Olivier Brissaud, Engineer 

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**General description**

The new micro spectro-gonio radiometer currently under developement will be optimized for the measurement at low temperature of bidirectional reflectance spectra, over the visible and near-IR (at least from 350 to 4800 nm), of dark and very small samples (organics, meteorites…) down to a few mm3 in volume.

[[sample holders]]:

It will have 2 major sample holder configurations:

- //Open sample holders// (various sizes) in //cold chamber// over -20°C ─ +20°C temperature range.

- The //SERAC environmental// cell with cryostats, pumps, pressure and temperature controllers, which allows us to introduce gas(es) of known composition and pressure (10-6 mb - 1 bar) over the sample and controlling and measuring the temperature over the -40°C ─ +80°C range. It will have a set of sample holders (small sizes) adapted to this new setup.

[[Tools and sub-systems]]:

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

- For samples preparation: another cold chamber (down to -20°C), set of sample holders, several specific tools for ice sample preparation,  2 sets of  sieves, grinders, mortars, saw, balances, microscope, owen, ultra-pure water, several pure gasses, wet chemistry materials a, several owens (up to 1200°C) for sample treatments.

- For the experiment: a thermodynamic volumetric system with high accuracy pressure gauges (10-6 to 1 bar), a flow meter (1-10 sccm) and pumps. He-Ne laser + detectors, camera for sample monitoring, …

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**Technical characteristics:**

[[Spectral range]] : 		0.35 - 4.5 µm (< 0.35 & > 4.8 µm: lower S/N) (4.2-4.3µm: atm. CO2 limited)
 
[[Spectral resolution]] : 	variable
 
- mini: 	< 0.1 nm (but S/N limited)
 
- maxi: 	3 nm (<700nm), 7 nm (<1600nm), 12 nm (<3000nm), 26nm (>3000nm) [May change with future new monochromator]
	
[[Bidirectional Reflectance]] 

- ''Incidence angle'': 0° to 75° ; resolution: 2° (can be reduced to 1°) ; maximum sampling : 0.1°

- ''Emergence angle'':	0° to 80° 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'': up to to 155° ; mini : ~ 7° for dark / fine grained samples 
	
- ''Illumination diameter'' (nadir): 7.5 mm 
- ''Observation diameter'' (nadir): 20 mm 

[[Photometry]]:	

''Absolute'': [will be determined during calibration and test phase end 2015 - 2016]

- 0.35-1.0 µm: 	expected better than 1% over all configurations (relative to a calibrated Spectralon 0.99 reference panel) 

- 1.0-2.5 µm: 	expected better than 1% over all configurations 
			
- 2.5-4.5 µm : 	expected better than 2% over all configurations 
			
''Relative'' : 

- better than 0.5% (0.35-4.5 µm)


[[File:micro-gonio_design-optique.jpg|500px]]

''Picture'': sketch of the micro spectro-gonio radiometer under building at IPAG

 	
[[Samples]]
 
''Types'': cosmo-materials, synthetic and terrestrial carbonaceous materials, minerals 

''Texture'': compact (dark) or granular (dark and/or fine grained < 200µm)  

''Grain size'': sub-µm to a 200 µm

''Size'': 

- 32 mm diameter (for full BRDF down to 75° observation)

- 8 mm x 32 mm (for principal plane observation down to 75°) 

- 8 mm x 16 mm (for principal plane observation down to 60°)
 
''Thickness'':

- 0.1 mm for dark & fine grained samples (< 20 µm)

- up to 5 mm for 'gray' & medium grained samples (< 200 µm)

- up to 10 mm for bright & medium/fine grained samples (< 100 µm)


[[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]]:	[will be determined during calibration and test phase end 2015 - 2016]	

- typical: 1 mn for 200 spectral channels in visible (S/N dependent) 					

- total: <1 hour for 100 spectral channels and 100 geometries 

[[Current state of system]]: 	

- Visible 0.3 - 1 µm range: under development, testing and buiding [2013-2015]. Ready for full testing end of 2015

- Infrared 1 - 4.8µm range: extension planned in 2015-2017 (if EPN2020-RI program accepted)
				
- low temperature: to be tested in cold room down to -20°C (end 2015)

  * Characteristics: Micro-Spectro-Gonio_characteristics.pdf **(TBD)**

  * Article: 

**Availability to community:**

//**2016-2017:**//

- Technical improvements/calibration (40%) 
				
- IPAG + associated laboratories measurements (60%)

//**after 2017:**//

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

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**References:**