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Interhelioprobe (IHP), an analogue to the ESA Solar Orbiter, is the prospective Russian space solar observatory intended for in-situ and remote sensing investigations of the Sun and the inner heliosphere from a heliocentric orbit with the perihelion of about 60 solar radii. One of several instruments on board will be the Bragg crystal spectrometer ChemiX which will measure X-ray spectra from solar corona structures. Analysis of the spectra will allow the determination of the elemental composition of plasma in hot coronal sources like flares and active regions. ChemiX is under development at the Wroclaw Solar Physics Division of the Polish Academy of Sciences Space Research Centre in collaboration with an international team (see the co-author list). This paper gives an overview of the ChemiX scientific goals and design preparatory to phase B of the instrument development.

We describe the RESIK (REntgenovsky Spektrometr s Izognutymi Kristalami) instrument, consisting of two double-channel X-ray spectrometers, designed to observe solar active region and flare plasmas. RESIK is one of the instruments making up the scientific payload of the Russian CORONAS-F solar mission. The uncollimated spectrometer uses two silicon and two quartz bent crystals observing flare, active region and coronal spectra in four wavelength bands with a resolving power (λ/Δ λ) of ∼1000. The wavelength coverage, 3.3–6.1 A, includes emission lines of Si, S, Cl, Ar, and K and in the third diffraction order, the wavelength range includes He-like Fe lines (1.85 A) and Ni lines (1.55 A) with dielectronic satellites, emitted during intense, hot flares. The instrument is believed to be the best calibrated space-borne crystal spectrometer flown to date. The spectrometer dynamically adjusts the data gathering intervals from 1 s to 5 minutes, depending on the level of solar X-ray emission at the time of observation. The principal aims of RESIK are the measurements of relative and absolute element abundances in the emitting plasma and the temperature distribution of plasma (differential emission measure) over the temperature interval 3 and 50 MK. This paper summarizes the scientific objectives of RESIK and describes the design, characteristics, and performance of the instrument.

We describe the RF15-I instrument, comprising a solar photometer and an imager, designed for multi-band high-time resolution measurements of integral solar fluxes in the energy range between 2 keV and 240 keV as well as for imaging of solar flares in the 2–8 keV energy range. The instrument was launched in August 1995 aboard the INTERBALL–Tail spacecraft. Description of the construction and operations is presented. The overall performance and the high sensitivity of the photometer are shown in examples. The X-ray tomograph-imager contains a unique rotationally modulated collimator. It provides sets of one-dimensional scans of flares taken at varying angles due to spinning of the satellite. We present principles of the algorithm for imaging from these data and show example of reconstructed flare image taken in the 2–4 keV range.