SeaWiFS
Sea-viewing Wide Field-of-view Sensor
Launched
Type
Mission End
Objective
Key OrbView–2 (SeaWiFS) Facts
- Orbit Type: Polar Sun Synchronous
- Altitude: 705 km
- Inclination: 98.2º
- Equatorial Crossing: Noon ± 20 min (until 2004, orbit not maintained)
- Period: 99 min
- Repeat Cycle: ~11 days (at launch, orbit not maintained)
- Design Life: 5 years (operated for 13)
The Sea-viewing Wide Field-of-View Sensor (SeaWiFS) was an ocean-color instrument carried aboard OrbView-2 (formerly SeaStar), developed by Orbital Sciences Corporation and launched into low Earth orbit on August 1, 1997, using a Pegasus launch vehicle. SeaWiFS was the satellite’s only scientific payload, and after spacecraft and instrument commissioning it started global data collection on September 18, 1997. Although originally designed for a minimum five-year mission, it operated successfully from 1997 to December 2010, when OrbView-2 lost communication with ground stations; the mission was formally concluded in February 2011. Over more than 13 years of operation, SeaWiFS produced one of the best continuous ocean biological records available.
SeaWiFS was designed to measure ocean color – specifically, the concentration of chlorophyll, the green pigment that enables photosynthesis in phytoplankton. From 1998 to 2010, it systematically mapped how “green” the oceans were. The mission’s primary objective was to obtain accurate, well-calibrated global ocean color data and convert them into meaningful biological parameters, such as photosynthesis rates, to better understand oceanic processes and their role in the global carbon cycle.
NASA purchased SeaWiFS data from Orbital Sciences. These data have been used for myriad applications. They helped clarify the magnitude and variability of chlorophyll and primary production by marine phytoplankton – microscopic marine plants that form the base of the ocean food web and play a central role in carbon uptake. Scientists could now track the timing of spring blooms (i.e., the time of highly abundant growth), and observe how phytoplankton populations respond to sunlight, nutrients, ocean currents, temperature, and climate patterns such as El Niño and La Niña. SeaWiFS data were also used to offer real-time monitoring of harmful algal blooms (red tides). They also provided crucial input to studies of ocean productivity, offering important insight into the role of ocean plants in carbon dioxide removal from the atmosphere, and links between marine ecosystems and climate variability. Finally, as a result of pre-launch modifications, SeaWiFS data were also used to measure vegetation index on land – leading to the production of a first-of-its-kind global snapshot of Earth’s biosphere.
The legacy of SeaWiFS lives on in current ocean color instruments and missions. The scientific and technical experience gained from the SeaWiFS mission have been valuable preparation for the design and application of the Earth Observing System's Moderate Resolution Imaging Spectroradiometer (MODIS), the Joint Polar Satellite System’s (JPSS) Visible Infrared Imaging Radiometer Suite (VIIRS), and the Plankton, Aerosol, Clouds and ocean Ecosystem (PACE) mission.
Spacecraft and Instrument Details
SeaWiFS was the only instrument on OrbView–2 (formerly SeaStar) spacecraft, which was built by Orbital Sciences Corporation. The spacecraft’s orbit allowed it to complete 14.5 pole-to-pole swaths of data each day and scan 90% of Earth’s surface every two days.
The SeaWiFS instrument consisted of an optical scanner and an electronics module (line drawing). It had scanning mechanisms that drove an off-axis folded telescope and rotating half angle mirror. The collected radiation is separated into four wavelength intervals—each of which encompasses two of SeaWiFS eight spectral bands, which were defined as follows:
| Instrument Bands | |
| Band | Wavelength |
| 1 | 402-422 nm |
| 2 | 433-453 nm |
| 3 | 480-500 nm |
| 4 | 500-520 nm |
| 5 | 545-565 nm |
| 6 | 660-680 nm |
| 7 | 745-785 nm |
| 8 | 845-885 nm |
Data Access
The SeaWiFS Project developed and operated a research data system that processed, calibrated, validated, archived, and distributed data received from an Earth-orbiting ocean color sensor. To learn more about SeaWiFS data see: https://www.earthdata.nasa.gov/data/instruments/seawifs.
End of SeaWiFS
After 13 years of service, researchers are no longer able to communicate with SeaWiFS. This extremely important instrument, which gave scientists data on ocean color, filled in a vital information gap. Subtle changes in ocean color signify various types and quantities of marine phytoplankton (microscopic marine plants), the knowledge of which has both scientific and practical applications.
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