The SPIRIT X-ray telescope/spectroheliometer successively operates on-board the Coronas-F satellite since August 15, 2001. The instrument includes two XUV-solar telescopes - one is a four-band Ritchey-Chretien telescope (171, 195, 284 and 304 A) with the optics analogous to the EIT SOHO telescope, another a Herschel two-band (175 and 304 A) telescope with off-axis paraboloids. The last one can operate as an XUV-coronagraph with "artificial moons" in the field up to 3 R (sun). The spectroheliometer includes two MgXII (8,42 A) full-Sun imaging spectrometers, two XUV spectroheliometers with objective grazing incidence diffraction gratings, each has two selectable spectral bands 177-207 and 285-335 A, and Bragg crystal FeXXV (1,85-1,87A) imaging spectroheliometer. During the first year there were observed flares and highly variable active structures in hot 10MK MgXII images, solar XUV-corona, full-Sun XUV spectral images, first separated images of solar disk and corona in the Hell and SiXI lines (303,78 and 303,32 A).

Radiographic images in ≈3.5-MeVdd-neutrons are obtained using a CCD detector for visualization. It is shown that radiographic images with a space resolution of ≤1 mm and 150-mm field of view at an exposure time of ≈5 min can be produced. Features of the radiography with a point neutron source of the generator type are considered.

The method of imaging XUV spectroscopy was used to study plasma in the transition layer and inner corona of the Sun with temperatures 105–107 K in the TEREK and RES experiments on board KORONAS-I. The observations were carried out in the period from March 12 to July 5, 1994. The spectral images and their correlation with the YOHKOH X-ray images and groundbased observations are important for the study of the physical conditions and modeling of the bulk processes in the quiet Sun plasma, including active regions, corona holes, and overlimb structures.

The TEREK-K telescope and the RES-K spectroheliometer aboard the KORONAS-I spacecraft were used to study the solar upper atmosphere by X-ray and XUV imaging spectroscopy in the 0.84-30.4 nm band. More than 2000 images of the Sun were taken between March 12 and July 5, 1994. New data on parameters of the solar plasma were obtained in the temperature range 10(5)-10(7) K and at heights from the transition zone to the upper corona. A description of the instruments and a summary of observing sessions are given.

Two x-ray spectroheliographs have been designed for obtaining solar images in about 8.42 angstrom and in 1.86 angstrom spectral regions with high spatial and spectral resolution. In both devices unique optical elements-focusing Bragg crystal mirrors are used. Technologies of their production are described here. These mirrors were tested in the x-ray region for their iamging and dispersive properties. These calibration results are presented.

A neutron tomography technique with a coordinate resolution of several tens of micrometers has been developed. Our results indicate that the technique resolves details with dimensions less than 100μm and measures a linear attenuation of less than similar 0.1 cm−1. Tomograms can be reconstructed using incomplete data. Limits on the resolution of the restored pattern are analyzed, and ways to improve the sensitivity of the technique are discussed.

We discuss the Mg XII Lyα line profile measurements obtained, by means of Bragg crystal spectrometer aboard INTERCOSMOS 7 satellite. The design of this spectrometer allows to clearly resolve both components α½ and α3/2) of the Lyα spin doublet. The intensities of each of these components we derived by means of fitting two Voigt profiles to the measured Mg XII Lyα shape. More than 100 spectra were analyzed in this way providing the statistical information on the value of intensity ratio . Derived average value of a is close to the theoretically expected 0.5, but in many cases the value of a is significantly different from 0.5 (both lower and higher values occur). We present examples of the fit and the histograms showing correlations of a value with the values of other flare parameters. Present analysis consist the observational part of the larger paper under the preparation with Prof. R.W.P. McWhirter theoretical group.

On the basis of the experimental data obtained from the high resolution X-ray spectra for solar flares and active regions the Suprathermal electron model (SEM) was proposed. This model suggests the existance of the multitemperature structure of the solar plasma emitting Fe and Ca X-rays and the presence of additional electrons with low energies E ⩽ 10 keV and small densities ∼ 1–5% relative to the thermal component.

In Part IV of the series of papers about the analysis of the INTERCOSMOS 16 ADP spectra a method is developed to evaluate plasma densities from measured resonance, intercombination, and forbidden helium-like Mg xi line intensities, using plots of the so-called G and R ratios. The density is close to the low-density limit. For the active region McMath 14352 a correlation between mean plasma density and electron temperature has been found, in agreement with earlier results. In an appendix systematic differences between measured and calculated line fluxes in all bands A to F are discussed.

The Bragg-type, flat ADP crystal spectrometer, launched on board the INTERCOSMOS 16 satellite has been used for measurements of the X-ray spectra emitted from solar active region plasmas. During the period of the instrument operation (August–September, 1976) only a few active regions were present on the Sun (minimum of the solar activity). About 60 spectra have been registered. In the present paper using a spectrum averaged over 20 scans, we measured the wavelengths corresponding to the statistically significant spectral features seen in this spectrum in the wavelength range 9.14–9.33 Å. By comparison with the calculated line wavelengths and intensities predicted in the framework of the thermal model of the ‘average’ active region, we performed the identification of these features. Besides rather prominent resonance, intercombination, and forbidden lines of the He-like ion Mg xi, it was possible to identify the satellite lines which correspond to 1s2nl - 1s2p nl transitions from the states with n = 2, 3, and 4. The present paper is the first in a series dealing with the INTERCOSMOS 16 Mg xi spectra.