Service Interruption

Jobs | Contact Us

AMSR/ADEOS-II L1A Raw Observation Counts

Summary

The Advanced Microwave Scanning Radiometer (AMSR) instrument on the Japan Aerospace Exploration Agency's (JAXA) Advanced Earth Observation Satellite-II (ADEOS-II) provided global passive microwave measurements of land, ocean, and atmospheric variables for the investigation of global water and energy cycles.

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. Each half-orbit data granule consists of observation counts, antenna temperature coefficients, offsets for calculating antenna temperatures, calibration temperature counts, land/ocean flags, time, latitude, longitude, and navigation fields in Hierarchical Data Format (HDF).

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. It measures horizontally and vertically polarized radiance at 6.9, 10.65, 18.7, 23.8, 36.5, and 89.0 GHz; and vertically polarized radiance at 50.3 and 52.8 GHz. AMSR collected 290 data points per scan for the 6 GHz to 36 GHz channels and 580 data points per scan for the 89 GHz channel. Data are available via FTP, CD-ROM, DVD, or DLT.

Citing These Data

The following example shows how to cite the use of this data set in a publication. For more information, see our Use and Copyright Web page.

The following example shows how to cite the use of this data set in a publication. List the principal investigators, year of data set release, data set title and version number, dates of the data you used (for example, April 2003 to October 2003), publisher: NSIDC, and digital media.

Japan Aerospace Exploration Agency. 2005. AMSR/ADEOS-II L1A Raw Observation Counts V002, [list the dates of the data used]. Boulder, Colorado USA: National Snow and Ice Data Center. Digital media.

Overview Table

Table of Contents

1. Contacts and Acknowledgments
2. Detailed Data Description
3. Data Access and Tools
4. Data Acquisition and Processing
5. References and Related Publications
6. Document Information

1. Contacts and Acknowledgments

Investigator(s) Name and Title

Japan Aerospace Exploration Agency
Earth Observation Center
Chuo-ku, Tokyo, 104-6023
Japan

Technical Contact

2. Detailed Data Description

Format

Level-1A data are in HDF with the following contents:

• Header

  • Core metadata
  • Product-specific attributes

• Data fields

• Navigation and attitude data
• Observation counts
• Calibration temperature counts
• Antenna temperature coefficients
• Time
• Latitude
• Longitude
• Sun azimuth
• Sun elevation
• Earth incidence
• Earth azimuth
• Data quality

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.

File Naming Convention

This section explains the file naming convention used for this product with an example.

Example file name: A2AMS03011815MD_P01A0000000

A2AMSYYMMDDPPMX_KNLL0000000

Refer to Table 1 for the valid values for the file name variables listed above.

File Size

Each half-orbit granule is approximately 38 MB.

Spatial Coverage

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.

Spatial Resolution

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.

Temporal Coverage

2003-01-28 (00:03) to 2003-10-24 (20:50)

Temporal Resolution

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.

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.

Parameter or Variable

See the Level-1A Data Fields document.

Error Sources

The AMSR Instrument Description Web page provides details on potential errors associated with radiometer calibration.

3. Data Access and Tools

Data Access

Please see the AMSR/ADEOS-II Data at NSIDC: Order Data Web page to order AMSR products.

4. Data Acquisition and Processing

Sensor or Instrument Description

Please refer to the AMSR Instrument Description Web page.

Calibration

AMSR calibration is defined as the task for evaluation and adjustment of Brightness Temperature (T_B) data. Radiometeric calibration of the T_B data includes an absolute evaluation of the T_B value and relative evaluation of the scan bias. The T_B 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.

Data Acquisition Methods

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.

Data Source

The Japan Aerospace Exploration Agency (JAXA) processes AMSR Level 0 data into Level-1A observation count data.

Processing Steps

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 is 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 is edited to make the data for one scene. Initially, Level 0 data includes redundant data so the redundant data is 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 is chosen.

5. References and Related Publications

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.

6. Document Information

Acronyms and Abbreviations

The following acronyms and abbreviations are used in this document:

Document Creation Date

February 2007

Document Revision Date

Document URL

http://nsidc.org/data/docs/daac/amsr_l1a_raw_counts.gd.html