Calibration and Metrological Characteristics of Equipment for Satellite Monitoring of Geoeffective Solar Ultraviolet Radiation

Abstract

The results are considered of calibration of semiconductor detectors of the VUSS-E spectrophotometer intended for monitoring the solar ultraviolet radiation flux in the Lyman-alpha line (L$\alpha$, 121.6 nm) on Roshydromet geostationary satellites. The calibration was carried out at the Kosmos metrological station at the Siberian International Center for Synchrotron Radiation in the channel of the VEPP-4 relativistic electron storage ring. The contribution $P$ to the VUSS-E signal from the L$\alpha$ line and from the spectral region above $\sim$122 nm is calculated using the model ultraviolet radiation spectra. It is shown that the value of $P$ can vary greatly for different sensors and different levels of solar activity: $P\sim 30{-}60$% at a low level and $P\sim 50{-}70$% at a high level of solar activity. This result indicates a need to calibrate all channels of each flight instrument and to take into account the dependence of the contribution $P$ to the VUSS-E signal from the L$\alpha$ line on the level of solar activity when monitoring space weather.