Table 2. AVIRIS functional parameters. 
1.8 2.0 2.2 
(length (jim) 
2.32 um 
>f the Cuprite 
1 with the AIS 
ierived from a 
f the Cuprite 
ed spectrum 
:tance. (c) a 
>rite taken at 
2 |tm in which 
to produce an 
curve. The 
as a function 
ition a)(Goetz 
tures having 
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Lngs. 
xel basis from 
shows a single 
m taken from 
derived from 
11 32 images. 
. The spectra 
on contain an 
of kaolinite. 
ample from a 
The spectra 
e centered at 
:al associated 
A laboratory 
sample is 
he top of the 
es since this 
pure quartz, 
>tion features 
a weak Si-OH 
Spectrometer 
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et Propulsion 
spectrometer 
tional during 
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swath in 224 
he instrument 
er a NASA U-2 
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: future space 
the Earth's 
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our separate 
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3 (Figure 9) . 
Laboratory 
alunite- 
bearing 
sample 
Laboratory 
kaollnite- 
bearing 
sample 
2.03 2.10 2.15 2.20 2.25 2.28 
Wavelength 0*m) 
Figure 8. AIS image of Cuprite, Nevada showing 3x3 
pixel spectra of three representative surface units. 
Direct identification of the dominant mineral in each 
area can be made on the basis of the 2.0-2.3 um 
spectral response. Laboratory spectra of 
field-collected samples are also shown (broken 
lines), and they verify the AIS results. 
Figure 9. Optical layout of the airborne visible and 
infrared imaging spectrometer. 
Figure 10. Optical arrangement for SISEX. 
Each line array is contained within a liquid hydrogen 
dewar to provide detector cooling. The onboard 
calibration source is connected to the spectrometers 
by optical fibers provide two broadband intensities 
for determining light transfer characteristics, and a 
holmium oxide filter provides absorption lines for 
monitoring spectral alignment. 
Three of the spectrometer sections use 64-element 
indium antimonide line arrays for shortwave length 
infrared; one of the spectrometers uses a 32-element 
silicon line array for the visible-near-infrared 
region. 
Detailed modelling of the AVIRIS performance 
indicates that signal-to-noise ratios of 220 in the 
visible and 90 in the infrared will be achieved. 
These studies indicate that subtle absorption 
features in mineral spectra can be observed under 
operating conditions. 
Parameter 
Value 
Instantaneous field of view 
1.0 mrad 
Field of view 
30° 
Total scan angle 
33° 
CIFOV (20-km altitude) 
20 m 
Swath width (20-km altitude) 
11 km 
Spatial oversampling 
15 percent 
Cross-track pixels per scan 
(after resampling) 
550 
Spectral coverage 
0.4-2.4 )im 
Number of spectral bands 
224 
Spectral sampling intervals 
9.4-9.7 nm 
Data encoding 
10 bits per.pixel 
Data rate 
17 Mbits/s 
Table 3. SISEX functional parameters. 
Parameter 
Value 
CIFOV 
30 m 
Swath width 
Spectral sampling interval: 
12.1 km 
VNIR 
10 nm 
SWIR 
20 nm 
Spectral coverage 
0.4-2.4 fim 
Field of view 
2.8° 
Raw data rate 
103 Mbits/s 
Data rate with editing 
Radiometric precision (NEAR): 
< 50 Mbits/s 
VNIR 
0.5 percent 
SWIR 
Steerable pointing: 
1.0 percent 
Along-track 
+ 60° 
Cross-track 
Focal plane: 
-30° 
VNIR 
silicon CCD, 64 X 404 elements 
SWIR 
HgCdTe/CCD hybrid mosaic 
6-64 x 64 devices butted to 
form 64 X 404 array 
(with 4 pixel gaps) 
The development and construction of spaceborne 
imaging spectrometers is underway. The Shuttle 
Imaging Spectrometer Experiment (SISEX) uses area 
array detectors for the visible and near infrared as 
well as the shortwave length infrared region and 
covers the spectrum from 0.4-2.5 (im. This instrument 
system, under development at the Jet Propulsion 
Laboratory, is planned for a shuttle flight in 1991. 
The SISEX functional parameters are given in Table 3. 
SISEX makes use of prisms in the place of gratings, 
and an all-reflective optical system. The SISEX 
optical configuration shown in Figure 10 is 
designated the dual-beam triple Schmidt-Littrow 
imaging spectrometer. The design incorporates three 
Schmidt cameras, one for the fore-optics and two for 
the spectrometer. 
Finally, a high-resolution imaging spectrometer 
(HIRIS) is envisioned for NASA's Earth Observing 
System to be placed aboard the polar-orbiting Space 
Platform in the mid-90s. HIRIS will have a ground 
instantaneous field of view of 30 meters and a 
spectral sampling interval of about 10 nm in the 
visible and the shortwave length infrared. The swath 
width of 50 km will be steerable to permit multiple 
scene revisits as often as every eight days. 
6 SUMMARY 
Broad-band multispectral scanners have already proven 
valuable for lithologic mapping for mineral 
exploration. High resolution (narrowband) systems, 
both profilers and imaging spectrometers, make 
possible the direct identification of minerals and 
provide a powerful method for mapping fine-grained 
hydroxyl bearing minerals, as well as carbonates and 
sulphates, that is often difficult to do on the 
ground. Imaging spectrometers now becoming 
operational will make it possible to develop 
mineralogical maps, heretofore unattainable, that can 
provide the basis for new models in mineral 
exploration.