Borstad Associates Ltd. - Shortwave Infrared Full Spectrum Imager (SFSI)

Shortwave Infrared Full Spectrum Imager (SFSI)

SFSI is a pushbroom line imager and as such uses no moving parts in the imaging process. All spectral bands for all pixels are imaged simultaneously. This is accomplished by using a two-dimensional array in which the spectra are dispersed over the 'vertical' dimension of the array and the across-track line of pixels is imaged onto the 'horizontal' dimension. SFSI was manufactured in 1990 by CCRS, Ottawa, Ontario, Canada and was rebuilt and upgraded by Borstad Associates Ltd. in 1998.

SFSI employs a two-dimensional platinum silicide Schottky barrier CCD array with 488 rows of 512 detector elements. In operation, a region of 480 lines by 496 columns is used; two adjacent lines are summed together on the detector to yield an effective array of 240 by 496 detector elements. This gives 240 spectral bands for each of 496 pixels in the across-track dimension for each integration period, which is hardware selectable by various clock speeds (40 - 67 ms). The data are digitized to 13 bits and recorded as 16 bits.

The optical train is f/1.8 and entirely refractive; the spectral dispersive component is a blazed transmission grating. The across-track pixel instantaneous-field-of-view (IFOV) is 1.2 mrad giving an across-track field-of-view (FOV) of 34°;. The along track IFOV is currently 3.5 mrad. This is determined by the slit width which has been set so that the slit image is approximately equal in width to the effective detector size (100 µm) in the spectral dimension. This arrangement maximizes signal strength without compromising spectral resolution, which is nominally 10.3 nm at full-width-half-maximum.

SFSI conceptual diagram


Operators Console	SFSI Camera Head

Specifications of the Borstad Associates Ltd. SWIR Full Spectrum Imager (SFSI)

Effective Spectral range	1230 to 2380 nm
Spectral resolution	10 nm
Number of pixels	496
Cross-track Spatial resolution	1.2 mRadian
Number of useful bands	230
Along-track Spatial resolution	3.5 mRadian
Field of View	32.8 degrees
Integration times	Hardware selectable clock speeds (40 - 67 ms)
Digitization	13 bits on chip
Data recording	Hard disk as 36 Gigabyte striped set.
Borstad Auxiliary equipment	two axis mechanical gyro, Leica GPS receiver, single broad band illumination sensor on top of aircraft recording to SFSI CPU.
Camera head	53 Kg 42 x 102 x 32 cm
Instrument Control Unit	17 Kg 48 x 48 x 18 cm
Power supply unit	17 Kg 49 x 40 x 14 cm
Video monitor	8 Kg 46 x 10 x 35 cm
Power	15 Amps 28VDC for a 700 Watt Flitetronics DC/AC inverter

Click HERE to view paper: G.A. Borstad, J. Lim, R. A. Neville, and P. Hauff, 2000. "SFSI-2 - a New Source of Airborne Hyperspectral SWIR Imagery."

Click HERE to view paper: G.A. Borstad, 2000. "Hyperspectral Mapping of Cuprite, Nevada with CASI and SFSI-2 Fused Data."

Click HERE to view paper: R.A. Neville et al, 1997. "Spectral Unmixing of SFSI Imagery in Nevada."

Click HERE to view paper: G.A. Borstad and R.A. Neville et al, 1995. "Comparison Of Mineral Maps Produced From SFSI Data with Those from AVIRIS Data."

Click HERE to view paper: P. Hauff et al, 1995. "The CCRS SWIR Full Spectrum Imager (SFSI): Mission to Nevada June 1995."