The Sky Monitor consists of many instruments, some of which are used as inputs into our radiative transfer code and some of which record sky and weather conditions.
- Exotech radiometer model 100BX containing four different spectral filters which coincide with the first four bands of Landsat TM.
- An Eppley pyronometer (Model 8-48) is used to measure downwelling irradiance.
- The Line of Sight Radiometer (LOSR) is pointed at the sensor we are calibrating to detect any changes in the atmosphere that might exist at the time of overpass. A filter at 860 nm is used in the LOSR because this wavelength shows the greatest contrast between clouds and a clear sky.
- A Vaisala thermometer, relative humidity sensor and an extended range Setra barometer are also included in the constant panel setup. The temperature, pressure, and relative humidity are used as inputs into our radiative transfer code.
The data are collected with a Fluke Hydra 2625A Data Logger using the accompanying Logger program which runs on a Tandy 4860 HD notebook computer. Data are collected every thirty seconds from the time the equipment is set up until thirty minutes before overpass. At this time, we begin taking continuous data until thirty minutes after overpass. We usually break down the Sky Monitor setup after this time but if not, we collect data again at thirty-second intervals. Data are collected as voltages, and these must be converted into the actual physical quantities they represent before we can use them as inputs into the radiative transfer code.