Space Solar Patrol: Absolute measurements of ionizing solar radiation

More accurate ionospheric and thermospheric models require permanent monitoring of the ionizing radiation from the full solar disk at high radiometric accuracy.The development and construction of the Space Solar Patrol instrument occurred from 1996 to 2003. This experiment has been built for permanent absolute measurements of the ionizing (extreme ultraviolet (EUV) and soft X-ray (X)) solar radiation from the full disk of the Sun. Every 72 s a spectrum from 0.14 to 198 nm will be recorded with a resolution of <1.0 nm. The Space Solar Patrol set of instrumentation consists of two radiometers and two grating spectrometers, an EUV spectrometer at normal incidence and a X/EUV spectrometer at grazing incidence. Their detectors are open secondary electron multipliers produced at the Vavilov State Optical Institute.In this publication, details of the Space Solar Patrol apparatus are presented. The methodology for the absolute spectral measurements as well as the laboratory calibration including the application of a synchrotron source is also be described.