In this work, we describe the design and flight performance of the REFOS instrument (from Russian REntgenovskiy FOto Spektrometr; in English “X-ray Photo Spectrometer”). REFOS is a soft X-ray spectrophotometer that registers full-disk integrated solar spectra (“Sun as a star”). It operates on board the Impulse-1 nanosatellite, which was launched on 24 June 2023. REFOS has a 1.2 – 30 keV spectral range, a 0.123 keV nominal full width at half-maximum (FWHM) resolution at 5.9 keV, and a cadence of 16 s. We illustrate the instrument flight performance using the spectra of the X5.0 flare that occurred on 31 December 2023 at 21:55 UT. For this flare, REFOS registered a meaningful signal in all of its energy bins. Based on a comparison between the GOES and REFOS fluxes, we corrected the REFOS spectral sensitivity. Additionally, we assessed the quality of the calibration based on the shape of the continuum. The observed continuum allows diagnosing the plasma temperature, and the observed spectral lines allow studying abundances of the Mg, Si, S, Ar, Ca, Fe, and Ni.

Pin-hole camera as a soft X-ray solar telescope is presented. The instrument is aimed on imaging of flares in the solar corona with angular resolution up to 40''. It will allow to register temporal profiles of flares and determine spectra in soft X-ray. The telescope consist on pin hole 0.1 mm in diameter in tungsten disk, thin film Al/maylar filter and back illuminated CMOS based 2d detector. The telescope designed for 6 U cubesat. The instrument itself has dimension of about 0.5 U with extended tube from 20 to 50 cm length. Keywords: Pin-hole camera, solar corona, soft X-ray, cubesat.

Within the Universat program, a set of solar vacuum ultraviolet (VUV) telescopes has been developed for deployment on 6U nanosatellites. Telescopes are designed to get images of the solar corona. The spectral ranges of observations is considered, the characteristics of the nanosatellite from the point of view of the observations feasibility are opmized, the optical scheme of the telescope and VUV multilayer mirrors coatings and thin-film filters are modelled. Keywords: Nanosatellite, VUV, telescope, solar corona.

The specific aspects of the design and operation of space instruments for recording radiation and images in extreme ultraviolet (EUV) range of the spectrum are considered. The main factors affecting the reliability of VUV instruments are contamination, the tempereture regime, pressure changes, acoustic and mechanical loads at the launch stage, weightlessness, and radiation-induced damage. These factors are often interconnected and operate in a complex manner. The analysis of the influence of these factors on the operating characteristics of the instruments and the possibilities of its reduction is carried out.

This paper describes in detail a compact (2U format) telescope operating in the extreme ultraviolet range for studying the solar corona at a wavelength of 17.14 nm. The telescope objective has been built according to the Ritchey-Chrétien scheme with the following parameters: effective focal length of 381.3 mm, field of view of 2×2∘, and angular resolution of 11 in. Reflective multilayer Al/Be coatings were used, having 55% reflectance and a 0.4 nm spectral bandwidth. The wavefront rms error is 30 nm. An interferometric technique for controlling the shapes of the substrates and for adjusting the optical system and detector of the telescope assembly is described in detail.

Pin-hole camera as a soft X-ray solar telescope is presented. The instrument is aimed on imaging of flares in the solar corona with angular resolution up to 40 angular seconds. It will allow to register temporal profiles of flares and determine spectra in soft X-ray. The telescope consist on pin hole 0.1 mm in diameter in tungsten disk, thin film Al/maylar filter and back illuminated CMOS based 2d detector. The telescope designed for 6U cubesat. The instrument itself has dimension of about 0.5U with extended tube from 20 to 50 cm length.

A small space telescope intended for imaging the Sun on board CubeSat small spacecraft has been developed and produced in the form of a ground-based model. A compact two-mirror optical system has been proposed for the telescope and tested. Using it, high-quality images of the Sun can be obtained with an angular resolution of better than 4″ in the EUV spectral region of the solar spectrum, where the main radiation of active solar processes lies. The expected quality was simulated for images that cannot be experimentally obtained and investigated under the ground conditions. The ability of the telescope to record all principal phenomena of the solar activity (flares and eruptive prominences) has been confirmed.

Within the Universat program, a set of solar vacuum ultraviolet (VUV) telescopes has been developed for deployment on 6U nanosatellites. Telescopes are designed to get images of the solar corona. The spectral ranges of observations is considered, the characteristics of the nanosatellite from the point of view of the observations feasibility are opmized, the optical scheme of the telescope and VUV multilayer mirrors coatings and thin-film filters are modelled.

The results are considered of calibration of semiconductor detectors of the VUSS-E spectro- photometer intended for monitoring the solar ultraviolet radiation flux in the Lyman-alpha line (L, 121.6 nm) on Roshydromet geostationary satellites. The calibration was carried out at the Kosmos metrological station at the Siberian International Center for Synchrotron Radiation in the channel of the VEPP-4 relativistic electron storage ring. The contribution P to the VUSS-E signal from the L line and from the spectral region above ~122 nm is calculated using the model ultraviolet radiation spectra. It is shown that the value of P can vary greatly for different sensors and different levels of solar activity: P ~ 30-60% at a low level and P ~ 50-70% at a high level of solar activity. This result indicates a need to calibrate all channels of each flight instrument and to take into account the dependence of the contribution P to the VUSS-E signal from the L line on the level of solar activity when monitoring space weather.

The article considers the possibility of monitoring solar activity in the soft X-ray range on board the Yarilo nanosatellite. It is shown that, despite a number of technological difficulties associated with the features of nanosatellites, their use for solving such scientific problems has great prospects. Estimates of instrument dynamic range are given. The features of processing the output signal of the detector, the influence of temperature on its functioning, and ways to improve spectral resolution by optimizing the thermal interfaces of the device are considered.

We present a description of the recent advances in the development of the KORTES assembly—the first solar oriented mission designed for the Russian segment of the International Space Station. KORTES consists of several imaging and spectroscopic instruments collectively covering a wide spectral range extending from extreme ultraviolet (EUV) wavelengths to X-rays. The EUV telescopes inside KORTES will trace the origin and dynamics of various solar phenomena, e.g., flares, CMEs, eruptions etc. EUV spectra provided by grazing-incidence spectroheliographs will enable precise DEM-diagnostics during these events. The monochromatic X-ray imager will observe the formation of hot plasma in active regions and outside them. The SolpeX module inside KORTES will offer an opportunity to measure fluxes, Doppler shifts and polarization of soft X-ray emission both in lines and continuum. SolpeX observations will contribute to studies of particle beams and chromospheric evaporation. The instrumentation of KORTES will employ a variety of novel multilayer and crystal optics. The deployment of KORTES is planned for 2024.

Abstract The SOLPEX complex consists of two instruments for recording soft X-ray radiation from the Sun and is a part of the KORTES equipment, which will be installed on board the International Space Station. The first instrument is a fast-rotating multi-crystalagg spectrometer designed to record solar spectra in the range of 0.4–23 Å with a time resolution of no less than 0.1 s. The second instrument is a pinhole camera with a focal length of 58 cm. The camera has a field of viewof 2° × 2°, angular resolution of 2 arcmin, and time resolution up to 0.2 s. The energy range is determined by the input filter and is 1–10 keV; the energy resolution is 0.5 keV. The combination of these two instruments makes it possible to locate hot solar sources in the corona, determine their speed, and conduct spectral diagnostics.

The SOLPEX complex consists of two instruments for recording soft X-ray radiation from the Sun and is a part of the KORTES equipment, which will be installed on board the International Space Station. The first instrument is a fast-rotating multi-crystalagg spectrometer designed to record solar spectra in the range of 0.4–23 Å with a time resolution of no less than 0.1 s. The second instrument is a pinhole camera with a focal length of 58 cm. The camera has a field of viewof 2° × 2°, angular resolution of 2 arcmin, and time resolution up to 0.2 s. The energy range is determined by the input filter and is 1–10 keV; the energy resolution is 0.5 keV. The combination of these two instruments makes it possible to locate hot solar sources in the corona, determine their speed, and conduct spectral diagnostics.

The WSO-UV (World Space Observatory—Ultraviolet) space mission, optical design of the telescope, and main scientific instruments are briefly overviewed. A description of the photosensitive device of the WSO-UV mission based on a back-illuminated CCD with an antireflection coating is presented. Methods to improve the radiation resistance and reduce contamination on the CCD surface are described.

Представлено описание космического аппарата “Спектр-УФ”, краткое описание оптической схемы телескопа, основных научных приборов. Изложено описание фотоприемного устройств проекта “Спектр-УФ” на основе ПЗС с обратной засветкой и просветляющим покрытием, описаны меры, предпринятые для увеличения радиационной стойкости и уменьшения загрязнений на поверхности ПЗС.

The Interhelioprobe mission aims to investigate the inner heliosphere and the Sun from close distances (up to 0.3 AU) and from out of the ecliptic plane (up to 30°). In this paper we present the relevance of the mission and its main scientific objectives, describe the scientific payload, ballistic scenario and orbits of the spacecraft. Possibilities of scientific cooperation with other solar and heliospheric space missions are also mentioned.

Aims: Knowledge of properties of the Earth’s upper atmosphere is important for predicting the lifetime of low-orbit spacecraft as well as for planning operation of space instruments whose data may be distorted by atmospheric effects. The accuracy of the models commonly used for simulating the structure of the atmosphere is limited by the scarcity of the observations they are based on, so improvement of these models requires validation under different atmospheric conditions. Measurements of the absorption of the solar extreme ultraviolet (EUV) radiation in the upper atmosphere below 500 km by instruments operating on low-Earth orbits (LEO) satellites provide efficient means for such validation as well as for continuous monitoring of the upper atmosphere and for studying its response to the solar and geomagnetic activity. Method: This paper presents results of measurements of the solar EUV radiation in the 17 nm wavelength band made with the SPIRIT and TESIS telescopes on board the CORONAS satellites and the SWAP telescope on board the PROBA2 satellite in the occulted parts of the satellite orbits. The transmittance profiles of the atmosphere at altitudes between 150 and 500 km were derived from different phases of solar activity during solar cycles 23 and 24 in the quiet state of the magnetosphere and during the development of a geomagnetic storm. We developed a mathematical procedure based on the Tikhonov regularization method for solution of ill-posed problems in order to retrieve extinction coefficients from the transmittance profiles. The transmittance profiles derived from the data and the retrieved extinction coefficients are compared with simulations carried out with the NRLMSISE-00 atmosphere model maintained by Naval Research Laboratory (USA) and the DTM-2013 model developed at CNES in the framework of the FP7 project ATMOP. Results: Under quiet and slightly disturbed magnetospheric conditions during high and low solar activity the extinction coefficients calculated by both models agreed with the measurements within the data errors. The NRLMSISE-00 model was not able to predict the enhancement of extinction above 300 km observed after 14 h from the beginning of a geomagnetic storm whereas the DTM-2013 model described this variation with good accuracy.

This review presents the basic characteristics of the SPIRIT instrument onboard the CORONAS-F satellite, description of observation programmes, summary of observation sessions and scientific data obtained, as well as the main results in the research of hot coronal plasma, solar flares and the eruptive phenomena.