International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part Bl. Istanbul 2004
Table 1. ALOS characteristics.
Item Characteristics
Orbit Sun synchronous, Sub recurrent
Altitude 691.65 km
Recurrent period 46 days, sub-cycle: 2 days
Inclination 98.16 degree
Generated power More than 7 kW (end of life)
Weight Approx. 4,000 kg
Data recorder 96 G bytes, solid-state
Data link 240 Mbps (via DRTS)
120 Mbps (direct down link)
2. MISSION INSTRUMENTS
2.1 PRISM
The PRISM (Osawa, 1998) is the sensor mainly for mapping. It
consists of three sets of telescopes for forward, nadir and
backward view and each telescope provides 2.5m spatial
resolution. These specifications are given to generate precise
Digital Elevation Model (DEM), and to achieve the accuracy
for 1/25,000 scale maps. The PRISM will provide not only high
resolution, but also wide swath image up to 70km. The
PRISM's optics, which is three-mirror type, has no chromatic
aberration over wide field of view, gives us clear and sharp
images.
Table 2. PRISM characteristics (nominal).
Item Performance
Push broom with 8 CCDs for
each telescope.
Scanning Method
Wavelength 0.52 ~ 0.77 um
FOV > 7.6 deg
IFOV 3.61 prad
Swath Width
Spatial Resolution
MTF @ Nyquist freq.
70 km (nadir)
2.5 m (nadir)
0.27 for cross-track
0.21 for along-track
Stereo Imaging B/H=1.0
Pointing Angle + 1.5 deg
Quantization 8 bits
Forward look
Backward look
* We
Nadir look
QJ
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Satellite velocity
direction
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Figure 2. PRISM PFM on the ALOS at JAXA.
2.2 AVNIR-2
The AVNIR-2 is a successor to ADEOS/AVNIR (JAXA, 2004),
which was launched on 17 August 1996 by Japanese H-II
rocket. The AVNIR-2 has almost same optics and configuration
as the AVNIR. The main modification parts are detectors and
following electronics. These changes are given to achieve 10m
spatial resolution compared to 16m of the AVNIR. Another
modification from the AVNIR is pointing capability, which is
+44 degree from nadir in cross-track direction. Its flexible
pointing ability realizes frequent observation, e.g. every 48
hours in higher latitude area. Figure 3 and Table 3 show
AVNIR-2 overview and characteristics, respectively.
: Pointing mirror
i
Satellite velocity
direction
Earth sensors are not parts of AVNIR-2.
Figure 3. AVNIR-2 PFM on the ALOS at JAXA.
Table 3. AVNIR-2 characteristics (nominal).
Internati
Item Performance
Scanning Method Push broom with 1 CCD for
each band.
Wavelength band 1: 0.42 - 0.50 um
band 2: 0.52 - 0.60 um
band 3: 0.61 - 0.69 um
band 4: 0.76 - 0.89 um
FOV 5.8 degree
[FOV 14.28 prad
Swath Width 70 km (nadir)
Spatial Resolution 10 m (nadir)
MTF @ Nyquist freq. > 0.25
Pointing Angle + 44 degree from nadir
Quantization 8 bits
2.3 PALSAR
The PALSAR (Wakabayashi, 1998), which is developed in
cooperation with JAXA and METI/JAROS, has a variable off-
nadir capability between 10 to 51 degrees using active phased
array technique with 80 transmitting/receiving modules.
One of the major observation modes is “fine” mode. It is a high-
resolution mode and the common operating mode for
interferometric observation. ScanSAR mode enables us to
obtain up to 350km swath data with HH or VV single
polarization. Spatial resolution is about 100m in both azimuth
and range directions. Polarimetric mode will be operated in an
experimental basis. Polarization is changed in every pulse of
transmission signal, and dual polarization signals are
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