The SeaWiFS instrument has been modified to produce a bilinear response; the original sensitivity is maintained up to about 80% of the digital output range, and then changed discontinuously to extend the dynamic range substantially; the net result is no expected saturation over clouds (or bright sand, ice, etc.). For example, in the original design, Band 1 saturation (1023 counts) corresponded to an input radiance of about 13.6 mW per (cm um sr), with a linear response; now the response is linear up to radiance about 10.9 (about 817 counts), and changes slope above that point so that saturation is reached at about 60.1

The instrument has scanning mechanisms to drive an off-axis folded telescope and a rotating half-angle mirror that is phase-synchronized with, and rotating at half the speed of, the folded telescope. The rotating scanning telescope, coupled with the half-angle scan mirror arrangement, provides a design configuration that permits a minimum level of polarization to be achieved, without field-of-view rotation, over the maximum scan angle requirement of 58.3 degrees. The absence of field-of-view rotation permits the use of a multichannel, time-delay and integration (TDI) processing in each of the eight spectral bands to achieve the required SNR. This capability, in turn, allows a relatively small sensor collecting aperture and, therefore, results in a smaller and lighter instrument than would otherwise be required. Incoming scene radiation is collected by the folded telescope and reflected onto the rotating half-angle mirror.


Status: Operational
Satellite SeaStar
Launch Date: August 1997
Type: Imaging multi-spectral radiometers (vis/IR)
Measurements and Applications:  

Technical Characteristics

Resolution: 1.1 km
N. of Bands: 8
Wavebands: VIS: 0.40 - 0.68 µm,
NIR: 0.74 - 0.88 µm
Swath: 2800 km




SeaWiFS Web Page
Ocean Color Web