SHADOWS Micro Spectro-Gonio Radiometer

NOTE: this instrument has been delivered to Europlanet 31st August 2017 and is now available for TNA access

Type: Laboratory Experiment facility

Facility name: SHADOWS Micro Spectro-Gonio Radiometer
(Spectro-photometer with cHanging Angles for Detection Of Weak Signals)

Location:
Institut de Planétologie et Astrophysique de Grenoble
CNRS – Université Grenoble Alpes
Batiment D de Physique, 3rd level
124, rue de la Piscine
38400 Saint Martin d’Hères, France

Persons in charge:
Scientific: Bernard Schmitt, Research director & Pierre Beck, Assistant Professor, & Sandra Potin, PhD
Technical: Olivier Brissaud, Engineer

=> How to apply for a TA Visit?

References:  Potin et al. 2018


General description

The new SHADOWS micro spectro-gonio radiometer is optimized for the measurement of bidirectional reflectance spectra, over the visible and near-IR (from 400 to 4700 nm), of dark and very small samples (organics, meteorites…) down to a few mm3 in volume.

The instrument is located in a dark cold room that can be cooled down to -20°C. It is fully automatized and the data calibration and reduction are made with homemade softwares. Various types of measurements can be programmed: simple reflectance spectra at one geometry (but possibly varying with time, temperature, or physical/chemical process), full BRDF (only in open sample holder), limited angle BRDF spectra or at few wavelengths (SERAC cell), …


Technical characteristics:

Spectral range:
– 0.4 – 4.7 µm (< 0.4 & > 4.7 µm: lower S/N) (4.2-4.3µm: atm. CO2 limited)

Spectral resolution: variable
– mini: < 0.1 nm (but S/N limited)
– maxi: 6.4  nm (200 – 1400 nm), 12.8 nm (600 – 2500 nm), 25.8 nm (1100 – 3400 nm), 51.3 nm (> 2500 nm)

Bidirectional Reflectance:
Incidence angle: 0° to 70° (60° for bright samples) ; resolution: 2.9°; min. sampling : 0.1°
Emergence angle: 0° to 85°; resolution : ± 2.05° (options: 0.8°, 1.25°, 1.65° but lower S/N) ; min. sampling : 0.1°
Azimuth angle: 0° to 180° (more than half an hemisphere); resolution : ± 2.05° ; (options: 0.8°, 1.25°, 1.65° but lower S/N); min. sampling : 0.1°
Phase angle: 5° to 160°;  for bright samples: ~8 to 140°

Illumination diameter (nadir): 5.2 mm (1.7 mm with single fiber)
Observation diameter (nadir): 20 mm

Photometry:
Absolute:
– 0.4-2.5 µm: < 1% over all configurations   (relative to Spectralon© 99% reference panel)
– 2.5-4.7 µm: better than 2% over all configurations (relative to Infragold© reference panel)
Relative :
– better than 0.5% (0.4-4.7 µm)

Polarimetry options (still under test)
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

photo-SHADOWSPicture: SHADOWS instrument, showing all instrumentation and goniometer parts

Samples:
Types: minerals, fine grained ice, organics, meteorites … (from bright to very dark)
Albedo: < 0.0003 to 1 
Texture
: fine to very fine grained granular or compact
Grain size
: < 500 µm grain/crystal diameter;  < 150 µm with a single fibre
Sample size
:  D > 5.7 mm (for illumination at nadir);
D > 2 mm with a single fibre
L x l > 20.5 mm x 5.7 mm (for illumination up to 75°)
Thickness:
– 0.25 mm for dark & fine grained samples (< 25 µm)
– up to 2.5 mm for dark & medium grained samples (< 250 µm)
– up to 2.5 mm for ‘bright’ & fine grained samples (< 25 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:
– single spectrum: 70 min over the 400-4700 nm range @ 10 nm sampling (431 spectral channels)
– BRDF: 24h for 50 wavelengths and 180 geometries

Current state of system:
– 0.4 – 4.7 µm range: fully calibrated
– polarization: under test (not available for external users)
– low temperature: tested in cold room down to -20°C ; to be tested in SERAC down to -40°C

Links:
Characteristics:


Sample holders:

SHADOWS has currently 2 major sample holder configurations:

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

Sample holders (aluminum):
– cylindrical, d=  2 mm, h= 0.5 mm
– cylindrical, d=  3 mm, h= 1 mm
– cylindrical, d=  7 mm, h= 1 mm
– cylindrical, d=  14 mm, h= 1 mm
– cylindrical, d=  20 mm, h= 1 mm
– cylindrical, d=  20 mm, h= 2 mm
– cylindrical, d=  35 mm, h= 2 mm
– cylindrical, d=  35 mm, h= 5 mm
– rectangular, L= 14 mm, l= 7 mm, h= 1 mm
– rectangular, L= 35 mm, l= 7 mm, h= 1 mm

There is also a possibility to measure cohesive samples in diffuse transmission with a vertical sample holder and both arms positioned horizontally

– 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 has not yet a set of sample holders (small sizes) adapted to this new setup. but they can be built on request.

Sample holders (aluminum):
– rectangular, L= 80 mm, l=35 mm, h=10 mm
– rectangular, L= 80 mm, l=35 mm, h=6 mm
– rectangular, L= 80 mm, l=35 mm, h=3 mm
(smaller sample holders

– The MIRAGE environmental cell with pumps, heater, pressure and temperature controllers, which allows us to get high vacuum (<10-6 mb) or to introduce gas(es) of known composition and pressure (10-3 mb – 1 bar) over the sample and to control and measure the temperature over the +20°C ─ +300°C range.

Sample holders (black anodized aluminum):
– cylindrical, d=  2 mm, h= 0.5 mm
– cylindrical, d=  3 mm, h= 1 mm
– cylindrical, d=  7 mm, h= 1 mm
– cylindrical, d=  7 mm, h= 2 mm
– cylindrical, d=  10 mm, h= 1 mm
– cylindrical, d=  10 mm, h= 2 mm
– cylindrical, d=  12 mm, h= 3 mm
– cylindrical, d=  12 mm, h= 6 mm

– The ICEBERG environmental cell (under development) will allows us to to get high vacuum (<10-6 mb) and to control and measure the temperature over the 80K (-193°C) ─  290K (+17°C) range.

Sample holders (black anodized aluminum):
– cylindrical, d=  3 mm, h= 1 mm
– cylindrical, d=  7 mm, h= 1 mm
– cylindrical, d=  10 mm, h= 2 mm
– cylindrical, d=  12 mm, h= 3 mm
– cylindrical, d=  20 mm, h= 8 mm
– cylindrical, d=  36 mm, h= 20 mm

Tools and sub-systems:

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

– For samples preparation: a 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, 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, …

Availability to community:

– Technical improvements/calibration (35%)
– IPAG + associated laboratories measurements (45%)
– open as Europlanet 2020-RI facility (TNA) (~10%)
– open to specific collaborations w. funding (~10%)

For further information contact: Bernard Schmitt