Microtops II Sunphotometer
The Microtops II sun photometer is a 5 channel (440nm, 675nm, 870nm, 936nm, 1020nm), hand-held instrument for measuring the direct solar radiance using a 2.5° viewing angle. The Microtops II has been configured with five filters for the determination of aerosol optical thickness (AOT), including filters at 936nm and 1020nm for the measurement of the precipitable water vapour content. Additionally it contains a non-volatile memory allowing associating date, time, coordinates, solar angle, altitude, pressure and temperature to each data point. 
Measurement aims: To determine the aerosol loading/water vapour content and its temporal variability over the target area. The aerosol data will be used as an input to the Radiative Transfer Code (RTC) for the atmospheric correction of the satellite data.
Resolution: 0.1 W/m2
Set-up: Location and time should be set up at the beginning of the measurements
Transportation: 10 x 20 x 4.3cm – 600 gram
Power Requirements: 4 x AA Alkaline batteries
Traceability: The handheld Microtops II sunphotometers are returned to the manufacturer for annual calibration as part of the FSF quality assurance schedule