In this work, we describe flight performance and potential applications of the REFOS experiment (from ‘‘Russian REntgenovskiy FOto Spektrometr’’; in English ‘‘X-Ray Photo Spectrometer’’). REFOS registers full-disk integrated solar spectra in a spectral range of 1.2–30 keV, with a 0.123 keV nominal spectral resolution at 5.9 keV, and a cadence of 16 s. The instrument operated on board the Impulse-1 nanosatellite, which was launched on June 24, 2023. On October 23, 2023, REFOS established solar orientation and started to observe the Sun. On April 4, 2024, the solar orientation system of the Impulse-1 went out of order. Instruments similar to REFOS could be used for flare monitoring. The shape of the SXR continuum can be used for flare temperature diagnostics that is independent of elemental abundances. On the other hand, the comparison of the spectral line and continuum intensities provides a diagnostics of the absolute abundances of Mg, Si, S, Ar, Ca, Fe, and Ni. Finally, the REFOS data could be used to study how the Earth’s atmosphere absorbs X-ray emission.
Reva et al. (Mon,) studied this question.