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

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



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, …



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)


Micro-gonio design-optique.jpg

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)


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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