ASTER Sensor
ASTER is an advanced optical sensor comprised of 14 spectral
channels ranging from the visible to thermal infrared region. It will offer
scientific and also practical data regarding various fields related to the
study of the earth. The ASTER Sensor is composed of the following
radiometers.
 Visible and Near-Infrared Radiometer(VNIR)
VNIR Functional Parameters with spectral bands
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Band 1
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0.52~0.60 m
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Band 2
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0.63~0.69m
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Band 3
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0.76~0.86m
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Sterescopic band
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0.7 6~0.86m
Back ward looking
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・Radiometric Resolution
|
0.5％NE 
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・Geometric Re solution
|
15ｍ
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・Pointing Coverage
|
 24deg
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・IFOV
|
21.3rad(nadir
viewing)
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18.6rad(backward
viewing)
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・Ster eoscopic Imaging
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B/H*=0.6
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・Detector
|
5.000 el・ ォ
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・Radiometric Accuracy
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4％
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・Quantization Bit Number
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8bits
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・Scan Period
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2.2msec
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・MTF(at Nyquis t frequency)
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>0.25(cross-track)
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>0.25(along-track)
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*B /H Base to Height Ratio
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**VNIR selects 4.100 elements corresponding to 60 km
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Short Wave Infrared Radiometer(SWIR)
SWIR is an advanced high resolution multispectral
radiometer which detects reflected solar radiation from the earth surface in
the wavelength region of 1.6 - 2.43 um. SWIR also has the capability to
change the boresight in the cross-track direction by +/-8.55 degrees from
nadir, by using a pointing mechanism.
SWIR Functional Parameters with spectral bands
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Band 4
|
1.600~1.700m/0.5%
NE
|
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Band 5
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2.145~2.185m/1.3%
NE
|
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Band 6
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2.185~2.225m/1.3%
NE
|
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Band 7
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2.235~2.285m/1.3%
NE
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Band 8
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2.295~2.365m/1.0%
NE
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Band 9
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2.360~2.430m/1.3%
NE
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・Geometric Resolution
|
30m
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・Pointing Coverage
|
8.55deg
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・IFOV
|
42.6rad
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・Detector
|
2.048 effements pixels*6bands
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・Radiometric Accuracy
|
4%
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・Quantization Bit N umber
|
8bits
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・Scan Period
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4.398msec
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・MTF(at Nyqu ist frequency)
|
>0.25(cross-track)
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>0.20(along-track)
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・ Cooler Linear Drive Stirling Cycle Crycooler
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Thermal Infrared Radiometer(TIR)
TIR is an advanced spaceborne
radiometer with five spectral bands in the thermal infrared (8-12 um). Its
ability to measure thermal emission properties will be useful for locating
mineral resources, characterizing the land and sea surface, and observing the
atmosphere.
TIR Functional Parameters with spectral Bands
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Band 10
|
8.125~8.475m
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Band 11
|
8.475~8.82 5m
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Band 12
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8.925~9.275m
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Band 13
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10.25~10.95 m
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Band 14
|
10.95~11.65m
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|
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・Radiometric Resolution
|
NET:0.3K
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・Geometric Resolution
|
90m
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・Pointing Coverage
|
8.55deg
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・IFOV
|
127.8rad
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・Detector
|
50effements （HgCdTe）
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・Quantization Bit Numbe
|
12bits
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・Scan Period
|
4.398msec
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・MTF
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>0.25(cross-track)
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>0.20(along-track)
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・Scaning Method
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Mechanical Scaning
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(Oscillaating Mirror)
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・Cooler Linear Drive Stirling Cycle Crycool er
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The major
characteristics of ASTER are as follows.
It will acquire image data of the earth surface from the visible to thermal
infrared region.
Highest geometric and radiometric resolution for optical sensors have
been attained for all frequency bands.
Three-dimensional image data will be acquired on single orbits in the
near infrared region.
There will be mechanical pointing functions for obtaining an imaging view
angle of +/-8.55 degrees in the cross-track direction for SWIR and TIR,
and for obtaining +/-24 degrees cross track for VNIR.
A High reliability cooler with a design lifetime of 50,000 hours
will be installed in the SWIR and TIR.
The above characteristics will satisfy the needs of those concerned with
resources and environment problems.
ASTER Main Characteristics
|
Spectral Coverage
|
VNIR
SWIR
TIR
|
3 Bands
6 Bands
5 Bands
|
0.52-0.86m
1.60-2.43m
8.125-11.65m
|
|
Spatial Resolution
|
VNIR
SWIR
TIR
|
15m
30m
90m
|
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Radiometric Resolution
|
VNIR
SWIR
TIR
|
NE
NE
NET
|
 0.5%
0.5%-1.5%
0.3K
|
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Swath Width
|
60km
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Pointing Angle
VNIR
|
8.55
24
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B/H
|
0.6
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Visible and Near-Infrared
Radiometer
|
VNIR
|
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Short Wave Infrared Radiometer
|
SWIR
|
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Thermal Infrared Radiometer
|
TIR
|
The VNIR high-resolution radiometer observes targets using solar radiation
reflected from the earth surface in three visible and near-infrared bands.
The stereoscopic image sensor views 27.6 degrees backward of the Band 3
sensor in the same orbit. VNIR has a wide pointing capability of +/-24
degrees from nadir in the cross-track direction. The radiometer will be
calibrated in orbit using halogen lamps. |
