Instruments and Facilities
The Caltech imaging spectrometer system (also called a hyperspectral imager) consists of a quad-core processor and two sensors (f/2.5 aperture vertical slit cameras) co-boresighted on an optical bench. The system was custom-built by Headwall Photonics, Inc. and is field-portable.
- Rapid, non-destructive mineral or non-mineral material mapping of samples and outcrops
- Visible-near infrared sensor: CMOS array, 0.4-1.0 μm wavelength coverage, 5 nm spectral resolution, 1.625 nm spectral sampling
- Shortwave infrared sensor: MCT array, 0.9-2.6 μm wavelength coverage, 6 nm spectral resolution, 6 nm sampling interval
- Signal-to-noise ratio (SNR) >100 for all channels
- All measurements are made relative to Spectralon®and corrected for the absolute reflectance properties of Spectralon®
This instrument was purchased through cost-sharing between a NASA Planetary Major Equipment grant, a Rose Hills Foundation grant, and internal Caltech support.
Laboratory setup (microscopic mode)
The instrument is mounted on a custom rack built by Caltech looking downward with the field of measurement illuminated by a halogen slit lamp (output manually set up to 180 W). Images are acquired by moving the sample under the instrument with a fine motion-control stage to obtain images at spatial resolutions of ~71 μm/pixel (VNIR) and ~212 μm/pixel (SWIR).
- This instrument can acquire images over any stage or track that moves samples at a constant rate up to a few cm/s for offsite applications. We have experience interfacing with a GeoTek Multi-Sensor Core Logger aboard the JAMSTEC drilling vessel Chikyu.
- The instrument can be raised and lowered and the light source adjusted to accommodate samples of varying thicknesses.
The imaging system can be mounted on a Headwall-supplied tripod with a fine motion-control rotational stage to acquire panoramic images of outcrops from a few meters distance to infinity. While the precise spatial resolution varies with distance from the outcrop, the effective instantaneous field-of-view (IFOV) on target from a standoff distance of 20 m is 0.6 cm (VNIR) and 1.7 cm (SWIR).
- Our custom lightweight battery system can power the instrument for ~15 hours of continuous runtime with no need for a generator.
- The imaging spectrometer fits in an 80 L backpack, and other components are easily carried by 1-2 others.
- Calibration targets of varying reflectance levels assist in atmospheric removal and calibration of the data.