Solar Spectral Irradiance Measurements at 368 nm, 500 nm and 778 nm

A sunphotometer was used to measure the solar irradiance at three wavelengths from rockets and a balloon over a period of three years. The sunphotometer was developed at the Physikalisch-Meteorologisches Observatorium Davos (PMOD) and calibrated by an irradiance standard lamp. The measured solar irradiance agrees within + 1,5% and - 2,0% with Neckel and Labs measurements in the 1960s. Unfortunately, the measured variability cannot necessarily be assigned to solar origin because of insufficient calibration accuracy.