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The AMSR/ADEOS-II L1A Raw Observation Counts (AMSR-L1A) data set was processed from Level 0 science packet data by the JAXA Earth Observation Center (EOC) in Japan.
As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.
Japan Aerospace Exploration Agency (JAXA). 2007. AMSR/ADEOS-II L1A Raw Observation Counts. Version 3. [indicate subset used]. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center. http://dx.doi.org/10.5067/ADEOS-II/AMSR/AMSR-L1A.003.
Advanced Microwave Scanning Radiometer (AMSR)
Southernmost Latitude: -90° N
The sampling interval at the Earth's surface is 5 km for the 89.0 GHz channel and 10 km for all other channels. Spatial resolutions range from 5 km to 50 km.
2003-04-02 (01:36) to 2003-10-24 (20:50)
The scanning period is 1.5 s and the data-sampling interval is every 2.6 ms for the 6 GHz to 36 GHz channels, and 1.3 ms for the 89 GHz channel. AMSR collects 580 data points per scan for the 89 GHz channel and 290 data points per scan for all other channels.
Version 3. See the AMSR Data Versions Web page for previous version information.
Japan Aerospace Exploration Agency
Earth Observation Center
Chuo-ku, Tokyo, 104-6023
NSIDC User Services
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University of Colorado
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phone: +1 303.492.6199
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Level-1A data are in Hierarchical Data Format (HDF 4.2r1) with the following contents:
The dimension of observation count data is 290 observations by approximately 2022 scans for all channels except 89.0 GHz. The dimension of 89.0 GHz data is 580 observations by approximately 2022 scans. The number of scans may fluctuate slightly. Missing data are indicated by a value of -9999.999.
This section explains the file naming convention used for this product with an example.
Example file name: A2AMS03011815MD_P01A0000000
Refer to Table 1 for the valid values for the file name variables listed above.
|Variable for Granule ID||Explanation|
|PP||Path number at the observation start point (01 - 57)|
|M||M or R (M = regular process or reprocess, R = near real time process)|
|X||orbit direction flag (A = ascending, D = descending)|
|Variable for Product ID||Explanation|
|K||P or N (P = regular process or reprocess, N = near real time process)|
|N||0 (spare field)|
|LL||1A (for Level-1A)|
|0000000||0 (spare fields)|
Each half-orbit granule is approximately 38 MB.
Southernmost Latitude: -90° N
Northernmost Latitude: 90° N
Westernmost Longitude: -180° E
Easternmost Longitude: 180° E
AMSR is a conical scan sensor that sweeps the surface of the Earth at about ±90 degrees centered at the direction of the satellite flight. The swath width is about 1600 km.
The sampling interval at the Earth's surface is 10 km for the 6.9 GHz to 52.8 GHz channels, and 5 km for the 89.0 GHz channel. The spatial resolution of each channel is listed in Table 2.
2003-04-02 (00:03) to 2003-10-24 (20:50)
The scanning period is 1.5 s and the data-sampling interval is every 2.6 ms for the 6 GHz to 52.8 GHz channels, and 1.3 ms for the 89 GHz channel. AMSR collects 580 data points per scan for the 89 GHz channel and 290 data points per scan for all other channels.
A granule of AMSR is defined as a half orbit between the South and North Poles for its observed position on the Earth. An observed position of AMSR is not nadir but a little forward to the satellite flight direction. Therefore, a scan location shifts about 2.5 minutes earlier from the satellite nadir on the orbit, but its center is positioned to the satellite nadir. Each half-orbit granule spans 50 minutes.
See the Level-1A Data Fields document.
Please refer to the AMSR Instrument Description Web page
AMSR calibration is defined as the task for evaluation and adjustment of Brightness Temperature (TB) data. Radiometeric calibration of the TB data includes an absolute evaluation of the TB value and relative evaluation of the scan bias. The TB calibration also includes regular monitoring of radiometric noise and physical temperature. Geometric calibration evaluates the rough beam patterns, inter-channel co-registration, and absolute position accuracy, as well as regular monitoring of antenna rotation speed and attitude notation. Data quality evaluations were also performed on the quality of initial data, the soundness of all engineering values, and deductive algorithms.
AMSR provides geophysical information relevant to water by receiving weak microwaves naturally radiated from the Earth's surface and atmosphere such as atmospheric water vapor, precipitation, sea surface wind speed, sea surface temperature, soil moisture, sea ice extent, and snow water equivalent. AMSR observes microwaves instead of optical data, and it can observe from day to night, under any weather condition, and in the presence of clouds.
AMSR is an eight-frequency, total-power microwave radiometer with dual polarization (except two vertical channels in the 50 GHz band). Conical scanning is employed to observe the Earth's surface with a constant incidence angle of 55 degrees. Multi frequency measurement is performed by an array of primary horns. Calibration counts are obtained every scan by using the hot load target (around 300 K) and the cold-sky mirror to introduce the temperature of deep space (around 3 K). Table 3 summarizes the AMSR instrument specifications.
|Center Frequency (GHz)||6.925||10.65||18.7||23.8||36.5||50.3||52.8||89.0||89.0|
|Band Width (MHz)||350||100||200||400||1000||200||400||3000|
|Polarization||Vertical and Horizontal||Vertical||Vertical and Horizontal|
|3dB Beam Width (° )||1.8||1.2||0.65||0.75||0.35||0.25||0.25||0.15||0.15|
|Sampling Interval (km)||10×10||5×5|
|Temperature Sensitivity (K)||0.34||0.7||0.7||0.6||0.7||1.8||1.6||1.2|
|Incidence Angle (° )||
|Dynamic Range (K)||
2.7 - 340
|Swath Width (km)||
The Japan Aerospace Exploration Agency (JAXA) processes AMSR Level 0 data into Level-1A observation count data.
Level-1A processing is performed to derive geometric and radiometric information from edited AMSR data. AMSR Level 0 data pre-processing starts with a quality check for detecting missing data, then all data gaps are filled by dummy data, and then the interpolation of anomalous data is carried out. Once those pre-processing operations are performed, the observation data are extracted to a scene of a half orbit from pole to pole. If a scene is composed of several Level 0 data, the divided input data are edited to make the data for one scene. Initially, Level 0 data include redundant data so the redundant data are deleted before generating the scene data. In redundant deletion processing, the quality information on corresponding data is compared and the data of the higher quality are chosen.
Version 2 features empirical corrections to the Aqua scan azimuth and satellite flight direction. With corrected sun azimuth, sun elevation, earth azimuth, and earth incidence angles, the geometric accuracy of AMSR 89 GHz data improved to within 2 km, compared to Version 1 AMSR-L1A data.
The improved Version 3 AMSR-L1A product features empirical corrections to the co-registration parameters A1 and A2, and an updated parameter file used for correcting the AMSR 89 GHz position information. As a result, Version 3 AMSR-L1A data provide improved accuracy for the following: latitude and longitude, land/ocean flags, earth incidence angle, earth azimuth angle, sun azimuth angle, and sun elevation angle.
The AMSR Instrument Description Web page provides details on potential errors associated with radiometer calibration.
Earth Observation Research and Application Center (EORC). 2003. ADEOS-II:Midori-II Science Project. http://sharaku.eorc.jaxa.jp/ADEOS2/index.html. Accessed March 2004.
Japan Aerospace Exploration Agency (JAXA). 2003. AMSR Overview. http://www.eorc.jaxa.jp/en/index.html. Accessed March 2004.
Japan Aerospace Exploration Agency (JAXA). 2003. ADEOS-II Data Users Handbook. Tokyo, Japan: JAXA. View PDF file.
National Space Development Agency of Japan. Date unknown. ADEOS-II Reference Handbook. View PDF file.
For more information regarding related publications, go to the Research Using AMSR Data Web page.
The acronyms used in this document are listed in Table 4.
|AMSR||Advanced Microwave Scanning Radiometer|
|ADEOS-II||Advanced Earth Observing Satellite-II|
|DAAC||Distributed Active Archive Center|
|EOS||Earth Observing System|
|FTP||file transfer protocol|
|HDF-EOS||Hierarchical Data Format - EOS|
|IFOV||Instantaneous Field of View|
|JAXA||Japan Aerospace Exploration Agency (JAXA)|
|NASA||National Aeronautics and Space Administration|
|NSIDC||National Snow and Ice Data Center|
|URL||Uniform Resource Locator|