A study on the improvement of the future branch system

This study aims to suggest an improvement plan for the army branch system considering the development trend of weapon systems through a case analysis of the vision and major weapon systems for each army branch system in R.O.K army. In the future, with the development of science and technology, hyper-connected networks based on artificial satellites would be built, and mosaic warfare, which integrates multiple domains simultaneously, and weapon systems capable of performing all-weather multifunctional battles across land, sea, and air would emerge. As a result, the common areas of the Army, Navy, and Air Force would be expanded, and the division of each army or branch itself would become ambiguous. Hence, it will be inevitable to move away from the branch operation concepts that have been operational until now to seek the concept of jointness or integration. To study this phenomenon, based on the Korean Army Vision 2050 published by the Army, the transition process of the current Army branch system and the cases of vision and major weapon systems for each branch were analyzed. The results of the analysis confirmed that although new advanced complex weapon systems are being developed for each branch, relatively little change has been made to the system. In particular, with the advent of hybrid drones and intelligent autonomous combat robots that can simultaneously perform ‘Surveillance, Reconnaissance - Decision – Strike’, it is expected that the area of expansion and mutual redundancy of combat functions will be further deepened. Therefore, in connection with the development of the weapon system, we will seek a solution to improve the Army branch system in the future and clarify the implications for the Navy and Air Force in the future.

Visibility Predictions for Near-future Satellite Megaconstellations: Latitudes near 50° Will Experience the Worst Light Pollution

Megaconstellations of thousands to tens of thousands of artificial satellites (satcons) are rapidly being developed and launched. These satcons will have negative consequences for observational astronomy research, and are poised to drastically interfere with naked-eye stargazing worldwide should mitigation efforts be unsuccessful. Here we provide predictions for the optical brightnesses and on-sky distributions of several satcons, including Starlink, OneWeb, Kuiper, and StarNet/GW, for a total of 65,000 satellites on their filed or predicted orbits. We develop a simple model of satellite reflectivity, which is calibrated using published Starlink observations. We use this model to estimate the visible magnitudes and on-sky distributions for these satellites as seen from different places on Earth, in different seasons, and different times of night. For latitudes near 50° north and south, satcon satellites make up a few percent of all visible point sources all night long near the summer solstice, as well as near sunrise and sunset on the equinoxes. Altering the satellites’ altitudes only changes the specific impacts of the problem. Without drastic reduction of the reflectivities, or significantly fewer total satellites in orbit, satcons will greatly change the night sky worldwide.

THE ROA LASER STATION: FROM ARTIFICIAL SATELLITES TO SPACE DEBRIS TRACKING

The Royal Observatory of the Spanish Navy (ROA) is specialist in space geodesy since the beginning of the space race. In 1975 a laser station was installed at ROA in collaboration with the French CERGA (Centre de Recherches en Géodynamique et Astrométrie). Since 1980, ROA has operated that station by their own. This equipment routinely tracks artificial satellites equipped with retro-reflectors. In 2014 ROA opened a new field of research: tracking of artificial satellites currently not active and equipped with retroreflectors. This new area was a challenge given the poor orbital accuracies that are available for these objects as they were not tracked on a routine basis. This served as an approach to our final goal: to strictly monitor space debris, this is, any type of uncontrolled man-made orbiting objects. To fulfill the objective, since 2017, we made significant changes to our laser installation. The most important was the replacement of the old laser bench with two new ones. One transmitting 500 mW-pulses, and another laser bench with 25 W transmission power. The study for the installation of the later laser was financed through European Union (EU) H2020 fundings and granted by the Spanish Centre for Industrial Technological Development (CDTI). Although it allows the tracking of collaborative objects, it is ideal for tracking non-collaborative too. Tracking activities begin in November 2017. From then onward, non-collaborative objects are monitored on a regular basis. This work shows the modifications already made, and the results obtained until 2019.

Machine-learning based discovery of missing physical processes in radiation belt modeling

Real-time prediction of the dynamics of energetic electrons in Earth's radiation belts incorporating incomplete observation data is important to protect valuable artificial satellites and to understand their physical processes. Traditionally, reduced models have employed a diffusion equation based on the quasi-linear approximation. Using a Physics-Informed Neutral Network (PINN) framework, we train and test a model based on four years of Van Allen Probe data. We present a recipe for gleaning physical insight from solving the ill-posed inverse problem of inferring model coefficients from data using PINNs. With this, it is discovered that the dynamics of ``killer electrons'' is described more accurately instead by a drift-diffusion equation. A parameterization for the diffusion and drift coefficients, which is both simpler and more accurate than existing models, is presented.

Estimating the Earth’s Outgoing Longwave Radiation Measured from a Moon-Based Platform

Moon-based Earth observations have attracted significant attention across many large-scale phenomena. As the only natural satellite of the Earth, and having a stable lunar surface as well as a particular orbit, Moon-based Earth observations allow the Earth to be viewed as a single point. Furthermore, in contrast with artificial satellites, the varied inclination of Moon-based observations can improve angular samplings of specific locations on Earth. However, the potential for estimating the global outgoing longwave radiation (OLR) from the Earth with such a platform has not yet been fully explored. To evaluate the possibility of calculating OLR using specific Earth observation geometry, we constructed a model to estimate Moon-based OLR measurements and investigated the potential of a Moon-based platform to acquire the necessary data to estimate global mean OLR. The primary method of our study is the discretization of the observational scope into various elements and the consequent integration of the OLR of all elements. Our results indicate that a Moon-based platform is suitable for global sampling related to the calculation of global mean OLR. By separating the geometric and anisotropic factors from the measurement calculations, we ensured that measured values include the effects of the Moon-based Earth observation geometry and the anisotropy of the scenes in the observational scope. Although our results indicate that higher measured values can be achieved if the platform is located near the center of the lunar disk, a maximum difference between locations of approximately 9 × 10−4 W m−2 indicates that the effect of location is too small to remarkably improve observation performance of the platform. In conclusion, our analysis demonstrates that a Moon-based platform has the potential to provide continuous, adequate, and long-term data for estimating global mean OLR.

Evolutionary Optimization of Multirendezvous Impulsive Trajectories

This paper investigates the use of evolutionary algorithms for the optimization of time-constrained impulsive multirendezvous missions. The aim is to find the minimum- Δ V trajectory that allows a chaser spacecraft to perform, in a prescribed mission time, a complete tour of a set of targets, such as space debris or artificial satellites, which move on the same orbital plane at slightly different altitudes. For this purpose, a two-level design approach is pursued. First, an outer-level combinatorial problem is defined, dealing with the simultaneous optimization of the sequence of targets and the rendezvous epochs. The suggested approach is first tested by assuming that all transfer legs last exactly the same amount of time; then, the time domain is discretized over a finer grid, allowing a more appropriate sizing of the time window allocated for each leg. The outer-level problem is solved by an in-house genetic algorithm, which features an effective permutation-preserving solution encoding. A simple, but fairly accurate, heuristic, based on a suboptimal four-impulse analytic solution of the single-target rendezvous problem, is used when solving the combinatorial problem for a fast guess at the transfer cost, given the departure and arrival epochs. The outer-level problem solution is used to define an inner-level NLP problem, concerning the optimization of each body-to-body transfer leg. In this phase, the encounter times are further refined. The inner-level problem is tackled through an in-house multipopulation self-adaptive differential evolution algorithm. Numerical results for case studies including up to 20 targets with different time grids are presented.