Solar autocalibrating XUV-IR spectrometer system (SOLACER) for the measurement of solar spectral irradiance.

The accurate measurement of solar spectral irradiance (SSI) from space is challenging because it requires a system that can reliably exclude the impact of degradation on the instruments for the full duration of a long-term mission. The new Autocalibrating XUV-IR Spectrometer System (SOLACER) presented here meets this requirement. It is a compact and moderate-cost instrument that allows repeated onboard calibration of the spectrometers (SPs) providing SSI data of significantly increased accuracy. To this end, absolute radiometers and ionization chambers with proven long-term stability serve as primary irradiance detectors to determine the absolute SSI fluxes passing through a series of narrow- and medium-band filters with updated transmission. Consecutively cross-calibrated bolometers (BOSs) and highly sensitive photomultiplier tubes are used as secondary irradiance detectors. The new SOLACER instrument is designed to cover the spectral range from about 2-2800 nm with eight planar grating SPs. Adding total solar irradiance and BOS sensors adapted to observe the Earth's infrared emission and the reflected solar radiation, the global energy budget at the top of the atmosphere can be measured to provide data of higher absolute accuracy for climate modeling, too.