USGS EROS Archive - Radar - ALOS PALSAR Radar Processing System

Science Center Objects

The Advanced Land Observing Satellite (ALOS) was launched on January 24, 2006 by the Japan Aerospace and Exploration Agency (JAXA) and was operational until May 12, 2011. ALOS captured 6.5 million scenes during its five years of operation.

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ALOS PALSAR Republic of Botswana, Africa

Okavango Delta in the Republic of Botswana, Africa (06/16/2006)
(Public domain.)

 

The Advanced Land Observing Satellite (ALOS) was launched on January 24, 2006 by the Japan Aerospace and Exploration Agency (JAXA) and was operational until May 12, 2011. ALOS, also referred to as DAICHI, (the Japanese often give two names to each of their space projects; the names are used interchangeably in the JAXA literature), captured 6.5 million scenes during its five years of operation. The satellite provided high quality, Earth observation data for topographical mapping, disaster and environmental monitoring and climate change studies. ALOS (which carried PALSAR) was launched into the sun-synchronous orbit and revolved around the earth every 100 minutes, or 14 times a day. ALOS PALSAR returned to the original path (repeat cycle) every 46 days. The inter-orbit distance was approximately 59.7 km on the equator. The PALSAR was an active microwave sensor which was not affected by weather conditions and operable both day and night. It was based on a Synthetic Aperture Radar (SAR) carried onboard Japan’s first earth observation satellite (JERS-1). The PALSAR was a right-looking SAR using L-band frequency with a cross-track pointing capability of 18º – 55º.

PALSAR had the following 3 observation modes:

Fine mode:
This observation mode was most commonly used under regular operation. Its maximum ground resolution of 7m is one of the highest as a SAR (for comparison, SAR onboard JERS-1 was about 18m resolution) loaded on a satellite. Fine resolution mode gives 10 m spatial resolution in both range and azimuth (70 km of swath width, -25 dB of noise equivalent backscattering coefficient, and 25 dB of Signal-to-Ambiguity (S/A) ratio at a look angle of 35º).

ScanSAR mode:
ScanSAR mode enabled a switch off-nadir angle from 3 to 5 times (scan by the swath of 70km) to cover wide area from 250km (70 miles x 3 miles) to 350km (70 miles x 5 miles). For comparison, swath width of SAR onboard JERS-1 was about 75km. The ScanSAR mode offered more than 250 km width of SAR images at the cost of spatial resolution (100 m) but when an optimized orbit was used, one could revisit the same target area in less than five days.

Polarimetric mode:
PALSAR realized both horizontal and vertical polarization. PALSAR could also simultaneously receive horizontal and vertical polarization per each polarized transmission which is called multi-polarimetry. In addition, PALSAR could switch from horizontal to vertical polarization and vice versa at respective transmission pulse enabling four polarizations by doubling simultaneous polarization, a function called full polarimetry.

Polarimetric mode has a resolution of 30m on a 30 km swath, but offers a complete polarization scheme (HH/HV or VV/VH).

PALSAR Characteristics

ALOS PALSAR Characteristics

(Public domain.)

ALOS PALSAR Products

Level 1.0 - This product was generated from the raw observation data (Level 0) through data editing such as bit realignment and the addition of orbit information.

Level 1.1 - This is the product of Single-look complex (SLC) equally spaced on slant range (equal to the spacing of sampling measurement) generated after rendering SAR processing to level 1.0 product.

Level 1.5 - This is the product of Multi-look amplitude generated after rendering SAR processing to level 1.0 product, acquired in single polarization high resolution mode. The data are equally spaced on the ground.

Additional Information

ALOS Research and Application Project 

Access Data

An ALOS PALSAR searchable data archive is maintained at the US Geological Survey Earth Resources Observation Science (EROS) Center. Data may be downloaded by USGS personnel after registering with the Americas ALOS Data Node (AADN) located at the Alaskan Satellite Facility (ASF) in Anchorage, AK. To become an approved user please contact AADN's User Services Office at 907 474-2664 or uso@asf.alaska.edu.

EarthExplorer can be used to search, preview, and download ALOS PALSAR scenes. The collection is located under the Radar category.