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AMSR Instrument Description


AMSR
The AMSR instrument. Image courtesy of the Japan Aerospace Exploration Agency (JAXA).

Sensor or Instrument Description

The Advanced Microwave Scanning Radiometer (AMSR) was launched on board the Advanced Earth Observation Satellite II (ADEOS-II), also known as Midori-II, on 14 December 2002. AMSR was an eight-frequency, passive-microwave radiometer system with the ability to observe from day to night, under any weather conditions with less cloud effects. It measured horizontally and vertically polarized radiances at 6.9, 10.65, 18.7, 23.8, 36.5, and 89.0 GHz; and vertically polarized radiances at 50.3 and 52.8 GHz. Spatial resolution of the individual measurements varies from 5 km at 89 GHz to ~50 km at 6.9 and 10.65 GHz. AMSR was developed and launched by the Japan Aerospace Exploration Agency (JAXA) with close cooperation of U.S. and Japanese scientists.

AMSR improves upon past microwave radiometers. The spatial resolution of AMSR data doubles that of Scanning Multichannel Microwave Radiometer (SMMR) and Special Sensor Microwave/Imager (SSM/I) data. Also, AMSR combines into one sensor all the channels that SMMR and SSM/I had individually. The following table compares operating characteristics of AMSR with previous sensors:


Comparative Operating Characteristics of SMMR, SSM/I, AMSR-E, and AMSR
Parameter SMMR
(Nimbus-7)
SSM/I
(DMSP-F08, F10, F11, F13)
AMSR-E
(Aqua)
AMSR
(ADEOS-II)
Time Period 1978 to 1987 1987 to Present 2002 to Present 2003
Frequencies (GHz) 6.6, 10.7, 18, 21, 37 19.3, 22.3, 36.5, 85.5 6.9, 10.7, 18.7, 23.8, 36.5, 89.0 6.9, 10.65, 18.7, 23.8, 36.5, 89.0, 50.3, 52.8
Sample Footprint Sizes (km) 148 x 95 (6.6 GHz)
27 x 18 (37 GHz)
37 x 28 (37 GHz)
15 x 13 (85.5 GHz)
74 x 43 (6.9 GHz)
14 x 8 (36.5 GHz)
6 x 4 (89.0 GHz)
70 x 40 (6.9 GHz)
14 x 8 (36.5 GHz)
6 x 4 (89.0 GHz)

Note: On 25 December 2003, ADEOS-II experienced an instrument anomaly which terminated the collection of earth observation data by AMSR.


Key Variables

AMSR measured geophysical variables such as atmospheric water vapor, precipitation, sea surface wind speed, sea surface temperature, soil moisture, sea ice extent, and snow water equivalent.

Principles of Operation

AMSR acquired radiance data by scanning the Earth's surface conically or mechanically and rotating its antenna along the satellite path. The aperture diameter of AMSR's antenna is 2 m with a sampling interval of 10 km for the 6 GHz to 36 GHz channels and 5 km for the 89 GHz channel  It scanned conically at a nominal 55 degree angle of incidence on the Earth’s surface and had a swath width of 1600 km.

Operating Characteristics
Frequency (GHz) 6.9 10.65 18.7 23.8 36.5 89.0 50.3 52.8
Spatial Resolution (km) 50 25 15 5 10
Bandwidth (MHz) 350 100 200 400 1,000 3,000 200 400
Polarization Horizontal and Vertical Vertical
IFOV (km) 40x70 27x46 14x25 17x29 8x14 3x6 6x10
Incident Angle ~55 degrees
Cross Polarization below -2dB
Swath Width 1,600 km
Dynamic Range 2.7 - 340 K
Absolute Accuracy 1 K (1s)
Noise Equivalent change in Temperature (NEdT) 0.3 K - 1.0 K (1s) 2 K (1s)
Quanitization 12-bit 10-bit

Manufacturer of Sensor or Instrument

The Mitsubishi Electric Corporation developed AMSR through a contract with JAXA. For information on ADEOS-II the satellite, please see the Platform Description: ADEOS-II Web site.

Calibration

AMSR had a high-temperature calibration source (about 340 K) and a small reflector to acquire the radiant temperature of deep space (at about 3 K). This external calibration scheme was first introduced by the Special Sensor Microwave/Imager (SSM/I) on the Defense Meteorological Satellites Program (DMSP) satellites. Each feed horn, from 6.9-89 GHz, sees the calibration sources once per scan period.

Science Data Flow

Under normal operating conditions, Remote Sensing Systems (RSS) in Santa Rosa, California, received Level-1A data from JAXA via the NASA Jet Propulsion Laboratory (JPL) Physical Oceanography Distributed Active Archive Center (PODAAC). RSS generated a Level-2A resampled brightness temperature product and transmitted it via FTP to the Global Hydrology Climate Center (GHCC) AMSR Science Investigator-led Processing System (SIPS). The AMSR SIPS team processed the Level-2A data into Level-2B swath products and then into Level-3 daily, weekly, and monthly gridded products. The Level-2A, -2B, -3 products, associated metadata, production histories, quality assurance files, ancillary files, and Delivery Algorithm Packages (DAPs) were transferred to the National Snow and Ice Data Center (NSIDC) Distributed Active Archive Center (DAAC) for archival and distribution to users.

Data Access

For access to AMSR data from the ADEOS-II platform, please see the AMSR/ADEOS-II Data Web site.

List of Acronyms

The following acronyms and abbreviations are used in this document:

ADEOS-II Advanced Earth Observation Satellite II
AMSR Advanced Microwave Scanning Radiometer
DAAC Distributed Active Archive Center
DAP Delivery Algorithm Package
GHCC Global Hydrology Climate Center
IFOV Instantaneous-Field-of-View
JAXA Japan Aerospace Exploration Agency
JPL Jet Propulsion Laboratory
NEdT Noise Equivalent change in Temperature
NSIDC National Snow and Ice Data Center
PODAAC Physical Oceanography Distributed Active Archive Center
RSS Remote Sensing System
SIPS Science Investigator-led Processing System
SMMR Scanning Multichannel Microwave Radiometer
SSM/I Special Sensor Microwave/Imager

References

Earth Observation Research and Application Center (EORC). ADEOS-II Science Project. 2003. http://sharaku.eorc.jaxa.jp/ADEOS2/index.html.
Accessed March 2004.

Japan Aerospace Exploration Agency (JAXA). AMSR Overview. 2003. http://www.eoc.jaxa.jp/satellite/sendata/amsr_e.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.