Instrument: SeaWiFS Profiling Multi-Channel Radiometer

The SeaWiFS Profiling Multi-Channel Radiometer (SPMR) is a free-falling instrument that is equipped with two sensors, collecting the upwelling irradiance (Ed) and downwelling (Lu) radiance at the following 11 wavelengths: 324, 340, 380, 412, 443, 490, 510, 555, 565, 665, and 683nm. The unit is protected in a long case that contains the majority of the system's electronics, while the optical sensors are located at either end of the case and face in opposite directions (i.e., up and down). These sensors measure the irradiance in units of uW/cm2/nm and the radiance in units of uW/cm2/nm/sr. Tilt and pressure are recorded at the same frequency as the irradiance measurements (6Hz). The SPMR is accompanied by a deck reference sensor, called the SeaWiFS Multichannel Surface Reference (SMSR). This sensor is equipped with the same 11 wavelengths as the SPMR, and is based on the same electronics. Data acquisition is synchronized between the SPMR and the SMSR and is performed at the same (6Hz) frequency.