High-Altitude Pseudo-Satellite Research Articles

Transceiver design for high altitude pseudo satellite aided dual satellite systems

This work focuses on a dual satellite system (DSS) where two multiple spot beam geosynchronous satellites transmit simultaneously on the same frequency across all spot beams. The intra-satellite co-channel interference is managed through precoding, while the inter-satellite co-channel interference is managed with successive interference cancellation (SIC) at the user terminals. The SIC eliminates the strongest co-channel interference from an adjacent satellite while treating the remaining interfering signals as noise. The power required at the transmitter to achieve the desired data rate is formulated as a semidefinite programming problem and relaxed rank constraints. The SIC-based receivers are shown to achieve a better data rate than traditional detectors that treat co-channel interference as noise while saving transmit power at the satellites. Though SIC-based DSS achieves better throughput than a single satellite system, the receiver complexity is high. A high-altitude pseudo satellite (HAPS) aided DSS is proposed to address this issue. In the case of HAPS-aided DSS, users within each spot beam are served by a HAPS, and the HAPSs use SIC to detect signals from satellites. The user terminals in HAPS-aided DSS can use simple detectors as HAPS eliminates co-channel interference through precoding. The full-duplex HAPS-aided DSS is shown to outperform SIC-based DSS.

High-Gain Compact Circularly Polarized X-Band Superstrate Antenna for CubeSat Applications

In this letter, a concept of a high-gain circularly polarized X-band antenna employing a partially reflecting surface (PRS) has been presented. In the initial antenna analysis, the influence of parasitic element size in the PRS structure on antenna radiation pattern parameters has been investigated and the optimal arrangement of the elements has been identified. The proposed antenna provides a wide bandwidth of return loss above 10 dB of 20% (8–9.8 GHz) and circular polarization (CP) in a frequency range 8.35–8.95 GHz. The final design is compact (62 × 62 × 22.2 mm) and lightweight (29.7 g), which makes it suitable for use not only in CubeSat X-band communication systems but also in drones and high-altitude pseudosatellite applications.

Fuzzy Energy Management Scheme for a Hybrid Power Sources of High-Altitude Pseudosatellite

HAPS (high-altitude pseudosatellites) are flight machines, airplane type, generally without pilot which fly in a definite zone at 18-22 km altitude, providing communication and surveillance services. These flight machines do not leave the atmosphere, and their purpose is to maintain a constant flight level for as long time as possible in the interest zone (e.g., five years) to fulfill their mission. HAPS energetic system proposed in this paper has to feed the electric propulsion system of HAPS (12.5 kW) and also to feed on-board equipment (navigation, data links, scientific equipment, etc.). On-board energy sources have to maintain HAPS in the interest zone for long periods. For this reason, it is used in the present solar power sources. A part of the generated energy is consumed on board; the rest is stored daytime and consumed nighttime. So, the system is provided with energy generation systems and also with storage and management systems. HAPS energetic system is a hybrid type, with two or more power sources. In this case, power sources are photovoltaic panels are used daytime and fuel cell are used nighttime, and also, a battery and/or a supercapacitor is used in transition periods from day to night and in peak load periods. In this paper, an electric power system used nighttime is designed and analysed. In this situation, the primary power source is the fuel cell and the secondary power sources are battery and/or supercapacitor. There are used numerical simulations models, developed in Matlab/Simulink, for all hybrid power source components: fuel cell stack, battery system, supercapacitors, conversion system, and fuzzy logic power management system. For a part of these components, there are used existing simulation models in Matlab/Simulink, adapted to these simulation requirements, and for others, there are designed and implemented simulation schemes according to these simulation requirements. An important component of the hybrid power source is the power conversion system which adapts the power sources parameters to consumer input requirements. A fuzzy logic power management system is designed.

An AI-Based Planning Framework for HAPS in a Time-Varying Environment

A High-Altitude Pseudo-Satellite (HAPS) is a fixed-wing, solar-powered Unmanned Aerial Vehicle (UAV) developed to become a flexible alternative to satellites with fixed-orbits for monitoring ground activities over long periods of time. However, given its lightweight build and weak electro-motors, the platform is rather sensitive to weather and cannot fly around hazardous weather zones swiftly. In this work, we formulate the problem of planning missions for multiple HAPS as a hybrid planning problem expressed in PDDL+. The formulation also considers the problem of modeling the platform dynamics, the time-varying environment, and the heterogeneous tasks that need to be carried out. Additionally, we propose a framework that combines a PDDL+ automated planner with an Adaptive Large Neighborhood Search (ALNS) approach, developed to couple the automated planner with a meta-heuristic that is specific for the problem. The task and motion planning are done in an intertwined way within the framework, preserving hence a common decision/search space. We validate our approach with a third-party realistic simulator for HAPS, as well as with a set of benchmark tests, showing that our integrated approach produces executable mission plans.

Multi-objective Optimization for the Design of an Unconventional Sun-Powered High-Altitude-Long-Endurance Unmanned Vehicle

The use of High Altitude and Long Endurance (HALE) Unmanned Aerial Vehicles (UAVs) is becoming increasingly significant in both military and civil missions as High-Altitude Pseudo-Satellite (HAPS). Since this class of aircraft is usually powered by solar cells, it typically features unconventional configurations to maximize sun exposed surfaces. In the present paper, a Multidisciplinary Design Optimization (MDO) and a Multi-Objective Optimization (MOO) environment have been developed to provide a computational design tool for modeling and designing these unconventional aircraft in order to achieve as independent objectives the maximization of solar power flux, the maximization of the lift-to-drag ratio, and the minimization of mass. To this purpose, a FEM models generator, capable of managing unconventional geometries, and a solar power estimator, are suitably developed to be integrated within a multi objective optimization loop. The simultaneous use of MDO/MOO approaches, and Design Of Experiment (DOE) creation and updating principles, enables to efficiently take into account the multiple and contrasting objectives/constraints arising from the different disciplines involved in the design problem. The study is carried out by using two different commercial codes for multi-objective optimization and for structural and aeroelastic analyses respectively. The use of advanced MDO/MOO approaches revealed to be effective for designing unconventional vehicles.