We present a unique, homogeneous database of photometric measurements for Herbig stars spanning up to 23 years. It contains almost 50,000 UBVR observations of 88 Herbig stars. All data were collected at Mount Maidanak Observatory in Uzbekistan. This represents the longest homogeneous collection of accurate Herbig star photometry ever assembled. By analyzing the photometry of 66 Herbig stars observed for at least five seasons, we identified three groups of objects with different statistical characteristics of their photometric variability. The most numerous is Group I, which includes 41 members. These objects show low-amplitude, short-term activity and no long-term variability pattern. Group II consists mainly of UX Ori stars, which demonstrate large-amplitude decays lasting from days to months. The Groups I and II also have distinctive spectral coverage. The spectral types of Group I objects range from B0 to A0, whereas those in Group II span A2 to F9. A number of Group III members are UX Ori stars with low-amplitude variability, but others may not belong to young Herbig stars or may have variability due to mechanisms other than variable circumstellar extinction. Our main conclusion is that the basic patterns of long-term variability of young Herbig stars are mainly determined by variable circumstellar absorption, combined with different conditions of visibility of the star-disk systems.
The volume of information necessary to transmit on Earth, in space, and between satellites and ground stations is increasing. Satellites are planned to be connected to the global secured quantum network on low-Earth orbits, to be used for quantum communication at higher distances from our planet. Such applications require optical components like metallic mirrors for signal preparation and transfer. In this study, we report a systematic investigation on the silver-aluminium (Ag-Al) mixed mirrors designed for space missions. We show the Ag-Al mixed coatings preparation process and investigate their properties for various Al concentrations up to 15%. It was found that 5-8% of Al admixing leads to the formation of smooth mirrors with high reflectance (measured >90% vis-IR range). Mirrors were tested by low-energy proton irradiation at doses typical for low-Earth orbits. It was shown that the 8% Al concentration represents an optimal solution for high reflectance and proton-resistant mirrors.
Thermal management of lithium-ion batteries aboard CubeSats during eclipse phases in Low Earth Orbit (LEO) remains a persistent engineering challenge. Conventional electric resistance heaters consume scarce on-board power, reducing the energy budget available for payload operations. This paper presents a reduced-order, simulation-based digital-twin framework for a semi-passive thermal control subsystem based on Molecular Solar Thermal (MOST) energy storage, augmented with a perovskite (PvK) optical sentinel that provides an auxiliary, non-critical state-of-charge (SOC) proxy for Extended Kalman Filter (EKF)-based state estimation. The MOST material acts as a thermal battery: it is optically charged during sunlit arcs and releases stored heat on demand during eclipse via catalytic triggering. We develop a coupled model comprising (i) a simplified LEO orbital-thermal environment, (ii) a four-node lumped-parameter thermal network, (iii) a first-principles MOST SOC model with Arrhenius kinetics for self-discharge and catalytic release, (iv) a bang-bang control strategy with electric–heater backup, and (v) a PvK-sentinel measurement model with radiation-induced degradation. In this study, the 0°C battery limit is treated as a conservative thermal-margin threshold motivated by low-temperature Li-ion charging constraints, not as a hard survival limit. Simulations over ten consecutive orbits in a worst-case eclipse scenario (500 km, β=0∘) compare the MOST-assisted configuration against both a nominal 1W heater-only baseline and a requirement-compliant heater-only baseline sized to keep the battery above the threshold. Under the assumed design conditions, the MOST branch reduces electric–heater energy demand by approximately 22% (4.1Wh over ten orbits) relative to the requirement-compliant baseline. This is a system-level saving that combines direct MOST heat delivery with a control-band effect, and it is obtained at the cost of a higher peak backup-heater rating. The MOST branch is therefore interpreted as a heater-load reduction mechanism rather than as a standalone replacement for conventional thermal control. A per-orbit energy-balance audit verifies the physical consistency of the reported savings. A Monte Carlo analysis characterizes the sensitivity of requirement satisfaction to uncertain parameters(requirement-satisfaction probability of 35% for the nominal sizing and 58% for the compliant sizing) rather than demonstrating robust performance. A trade study against heater-only and a representative, non-optimized phase-change-material baseline suggests a potentially favorable mass–energy trade for the MOST approach within the specific design space considered here. The study is presented as a low-TRL, simulation-based feasibility and requirements-mapping assessment, not as a flight-qualified thermal-control design.
