Cosmic Research

In order to avoid emergency situation it is necessary to take into account impact of disturbances in space environment during launch of space vehicles. This paper examines changes in the neutral density of the thermosphere (ρ) according toSwarmsatellites and global electron content (GEC) from JPL GIM-TEC maps during 130Starlinksatellite launches in 2019-2023. The variations ofρ and GEC over the 24-hour period centered at the launch time were identified and analyzed. The spatial distribution and evolution of ρ and GEC in terms of solar activity, season and level of geomagnetic activity before and after eachStarlinklaunch event were investigated. It is shown that with increasing the phaseΦof the solar cycle (SC) fromΦ=0.5 (February 2022) to a maximumΦ=1 (April 2024) of SC25, the value ofGEC andρincreaseby 2.1 and 3.5 times, respectively. During this period, 75 magnetic storms of categories NOAA G1−G4 were observed at Kp≥5.0, of which 19 storms has occurred in the interval±24 hours from the moment ofStarlinklaunch. Only in one case an emergency was observed on February 3, 2022, during the launch ofS-36, when 38 out of 49 satellites left orbit during a minor two-phase geomagnetic storm of level G1 (Kp=5.3). Comparison is made with another successful launchS-77on March 23, 2023 during an intense magnetic storm of category G3 (Kp=7.3). It is shown that at theS-77launch the neutral density ρ prevailed in the northern high latitudes, while in the case ofS-36, the thermosphere was denser near the equator. AfterS-36launch, the transition from the positive to negative perturbation of GEC has happened while a strictly negative GEC anomaly was observed in the case ofS-77. The examples considered show that the intensity of a geomagnetic storm is not the only criterion for an emergency situation. Other characteristics should be taken into account when launching spacecraft, including an increase in electron content in the ionosphere and the density of the neutral atmosphere, accompanied by increased satellites drag at low orbits.

The neutron radiation of the lunar surface under the influence of energetic charged particle flux from the intense Solar Proton Event (SPE) is considered. Numerical estimates of the neutron flux and the corresponding neutron component of the radiation dose are made for the historical Carrington SPE, which can be considered an example of the most intense SPE recorded in the modern period of solar activity observations. It is shown that the neutron component of the dose during the Carrington SPE was approximately 1000 times higher than the background value from the impact of Galactic cosmic rays (GCR) on the lunar surface under quiet Sun conditions. The value of the total radiation dose on the lunar surface during the Carrington SPE was close to the limit values for humans in space.

Based on the results of numerical modeling and investigation of orbital structures in the lunar dynamic space, this article proposes an original orbital grouping of the lunar global navigation satellite system in quasi-frozen highly elliptical and highly inclined orbits. The proposed grouping has structural stability and provides effective navigation coverage. The search for such a configuration of the lunar GNSS was carried out by varying the positional orbital elements in wide ranges: the semimajor axis from 4 to 12 radii of the Moon, the eccentricity from 0 to 0.7, and the inclination from 40°to 65°.

This study presents a method for detecting anomalous measurements in the trajectory data of spacecraft, based on recursive partitioning of the time series of observations. This method analyzes the standard deviation of the data, effectively identifying anomalous measurements characterized by elevated noise levels. A significant advantage of this approach is the lack of requirement for prior knowledge of the initial orbital approximation and the absence of a need for pre-training. It has been tested on synthetic datasets with artificially introduced anomalies, as well as on real data from the “Spektr-R” spacecraft. The results demonstrated an accuracy of 96 % compared to other traditional anomaly detection methods. The algorithm of this method is applicable to various types of orbits and scales of observations. Its code is available for public use.