The Optical measurement system consists of two instruments of the SeaWiFS Profiling Multichannel Radiometer (SPMR) and the
SeaWiFS Multichannel Surface Reference (SMSR), as well as deck unit, winch and PC.
These instruments measure downwelling irradiance (Ed), upwelling radiance (Lu) and irradiance above the water surfaces (Es)
continuously. (Photosynthetic organisms are able to use only the specific spectral range of solar radiation in the process of
photosynthesis.) Upwelling radiance (Lu) is used to provide normalized water leaving radiance for SeaWiFS calibration and validation and
the empirical development of radiative transfer algorithms for the exploration of ocean color satellite data. Details for these
instruments are outlined below.
The SPMR measures vertical profiles of downwelling irradiance (Ed) and upwelling radiance (Lu) in 13-channel spectral bands, as
well as instrument tilt, fluorometry, conductivity and an external temperature sensor.
It is deployed in a freefall mode through the water column.
1) Measurement method : Freefall
2) Observation depth : 0-100m (1.00 m/s)
3) Tilt : less than 3 degrees
4) Ed and Lu sensor : 13 channels
5) Other sensors : Tilt meter, fluorometer, conductivity and external temperature probe
The SMSR measures irradiance above the water surfaces (Es) in 13-channel spectral bands, which also has tilt meter and an
internal temperature sensor. The SMSR is used for the derivation of the penetration of visible and ultra-violet light in the ocean, and
for the determination of the vertical distribution of apparent optical properties for comparison with in-situ pigment measurements.
1) Measurement method : As a reference sensor which mounted on the anti-rolling system's deck and never shadowed by any ship
2) Es sensor : 13 channels
3) Other sensors : Tilt meter
Observed data was analyzed by software and extinction rate and photosynthetically available radiation (PAR) were computed.