PALSAR:Phased Array type L-band Synthetic Aperture Radar

PALSAR has advanced functions and performance of the synthetic aperture radar on-board the first Japanese Earth Resources Satellite (JERS-1). It is an active microwave sensor imaging the earth day and night regardless of atmospheric weather conditions.

PALSAR has a high-resolution mode and a ScanSAR mode; with the latter mode, the instrument scans wide swaths of 250-350 km, depending on the number of scans, by changing the viewing angle. The swaths are three to five times wider than that of any conventional SAR system.
PALSAR is a joint development effort between JAXA and Japan Resources Observation System And Space Utilization Organization (JAROS).

PALSAR Main Specifications
Mode High resolution ScanSAR Polarimetric
Center frequency 1,270 MHz (L-band)
Bandwidth 28MHz 14MHz 14MHz , 28MHz 14MHz
Polarization HH or VV HH+HV or VV+VH HH or VV HH+HV+VH+VV
Range of incidence angles 8 - 60° 8 - 60° 18 - 43° 8 - 30°
Ground resolution 7 - 44m 14 - 88m 100m (multi look) 24 - 89m
Swath 40 - 70km 40 - 70km 250 - 350km 20 - 65km
Bit length 5 bits 5 bits 5 bits 3 or 5bits
Data rate 240Mbps 240Mbps 120Mbps,240Mbps 240Mbps
Noise-equivalent backscatter coefficient *2 < -23dB (Swath 70km)
< -25dB (Swath 60km)
< -25dB < -29dB
Signal-to-ambiguity (S/A) ratio *2 >16dB(Swath 70km)
>21dB(Swath 60km)
>21dB >19dB
Radiometric accuracy 1dB in scene, 1.5dB on orbit
Antenna size Azimuth direction: 8.9m x Elevation direction : 3.1m

*The areas beyond 87.8°N and 75.9°S with an off-nadir angle of 41.5°are unobservable.

*1 The operation time is limited due to power constraints.

*2 High resolution mode: an off-nadir angle of 34.3°
ScanSAR mode: an off-nadir angle of 34.1°
Polarimetric mode: an off-nadir angle of 21.5°

PALSAR data are available in Level 1.0, Level 1.1 and Level 1.5, which are generated by applying range and azimuth compressions to the acquired data.

■Definitions of processing levels of PALSAR products

Level Definition
1.0 This product provides slant range data as they are recorded; it is not processed to imagery. It requires a processing program before utilizing the data.
1.1 This is single-look slant-range imagery generated by applying range and azimuth compressions to the Level 1.0 data. Coordinates, phases and amplitudes are included.
1.5 The amplitude data, after range and azimuth compressions and multi-look process, are projected to ground range and then to a selected map. The pixel spacing can be chosen depending on the observation mode. The following correction options are available.
R:Map projection by geo-referencing.
G:Map projection by geo-coding (to make the true north up.)

PALSAR imagery

This image was taken in the vicinity of Kanagawa Prefecture by PALSAR. PASLAR transmits microwaves down to the earth and observes the returns from the ground surface. Since it observes the earth day and night regardless of weather conditions, it is useful for monitoring the collapsing of buildings and subtle changes to the earth surface resulting from land movements at the time of an earthquake or other disasters.


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