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Instrument: SEAWINDS : SeaWinds
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Associated Platforms

Spectral/Frequency Information
Wavelength Keyword: Microwave
Spectral/Frequency Coverage/Range: 13.4 gigahertz; 110-watt pulse at 189-hertz pulse repetition frequency (PRF)

Related Data Sets
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The SeaWinds scatterometer is a specialized microwave radar that measures near-surface wind velocity (both speed and direction) under all weather and cloud conditions over Earth's oceans. The experiment is a follow-on mission and continues the data series initiated in 1996 by the NASA scatterometer (NSCAT). The SeaWinds instrument was launched on the NASA QuikScat "quick recovery" satellite on June 19, 1999. SeaWinds was also launched on the Japan Aerospace Exploration Agency (JAXA) Advanced Earth Observation Satellite II (ADEOS-II) on December 14, 2002. ADEOS-II failed on October 24, 2003.

SeaWinds uses a rotating dish antenna with two spot beams that sweep in a circular pattern. The antenna radiates microwave pulses at a frequency of 13.4 gigahertz across broad regions on Earth's surface. The instrument will collect data over ocean, land, and ice in a continuous, 1,800-kilometer-wide band, making approximately 400,000 measurements and covering 90% of Earth's surface in one day.

Scatterometers use a highly indirect technique to measure wind velocity over the ocean. Changes in the wind velocity cause changes in ocean surface roughness, modifying the radar cross section of the ocean and the magnitude of the backscattered power. Multiple collocated measurements acquired from several viewing geometries (incidence angles, polarizations, and directions) are used to determine wind speed and direction simultaneously. The directly measured backscatter cross-sections over land and ice-covered regions yield information on vegetation type and ice type and extent.

Key SeaWinds Facts
Heritage: SeaSat, NSCAT
Dimensions: CDS: 32 cm ? 46 cm ? 34 cm; SES: 81 cm ? 91 cm ? 43 cm;
SAS: ~150 cm; 100-cm diameter antenna dish on 60-cm diameter ? 60-cm pedestal
Mass: 220 kg
Power: 220 W
Duty Cycle: 100%
Thermal Control: Radiators
Thermal Operating Range: 5\u201340 C
Field of View (FOV): Rotating (at 18 rpm) pencil-beam antenna with dual feeds pointing 40 and 46 from nadir
IFOV: ? 51 from nadir
Swath: 1800 km (? 51 look angles) from 803-km altitude
Pointing Requirements (3): Control: <0.3 (~1000 arcsec); Knowledge: <0.05 (~167 arcsec); Stability: <0.008/s (30 arcsec/s)

Online Resources

Instrument Logistics
Data Rate: 40 kbps
Instrument Start Date: 1999-07-19
Instrument Owner: USA/NASA

Data Rate: 40 kbps
Instrument Start Date: 2003-04-10
Instrument Stop Date: 2003-10-24
Instrument Owner: USA/NASA