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  • Open access
  • 148 Reads
Low Earth Orbit design for IoT satellites over Thailand

At present, communication technology is very important to daily life. Internet of Things (IoTs), especially, are going to play major roles in our daily life in the near future. However, users in some remote areas still cannot connect to the core network. Therefore, it is imperative to develop an IoT satellite system that can serve every user everywhere in the world, by using Low Earth Orbit satellites. The objective of this study was to theoretically investigate the feasibility of successful communication between a ground station and satellites. Among a number of basic parameters of satellite communication, trajectories and periods of fly-by of currently available satellites over Thailand were considered, as well as vernal equinox and ascending node angle, Mean Durations that satellite can receive and send data from ground stations, by operating the satellite in the height range 500, 550 and 600 km above the earth. An outcome of the investigation was a few sets of parameter values that were theoretically verified to produce feasible communication between ground station and satellite. The parameter values reported in this paper may directly benefit developers of new applications of satellite communication in their effort to design a proper communication scheme for their system.

  • Open access
  • 123 Reads
Calculation of link budget from LoRa ground sensor to IoTs satellite

LoRa is a Low-Power Wide-Area Network (LPWAN) technology for Internet of Things (IoTs) application. Its advantages are low power consumption, inexpensive equipment cost, highly- secure access, and most importantly, good for long-range communication. Currently, LoRa network are extensively deployed worldwide. In the near future, that LoRa gateway may not be able to provide sufficient coverage for the ever-increasing deployment. A solution is to move the LoRa gateway up high to the satellite. The objective of this study was to theoretically investigate the feasibility of successful communication between ground sensor and LoRa gateway mounted in a satellite. In this study, sets of transmission parameters were analyzed whether, in principles, they would be able to support such kind of communication setup. For example, LoRa communicated in the frequency band 923 – 925 MHz in Thailand. Modified mathematical expressions were derived for link budget calculation. Using certain assumptions and this mathematical model, we discovered that, in principles, a suitable set of transmission parameters would be able to make the link budget sufficiently high so that this communication scheme would be feasible. The findings from this study may directly benefit developers of new applications of LoRa and IoTs satellite in their effort to design a communication scheme for their system. Nevertheless, the discovered feasibility was from the standpoints of theoretical matters. A valid experiment is needed in a future research to actually confirm this feasibility.

  • Open access
  • 102 Reads
Contribution of Space Education in Deep Technological Development of Middle-income Countries: A Case Study of MOOC in Thailand

Innovation enhancement strategies in middle-income countries are usually limited by several challenges including knowledge attainment, business opportunities, and information infrastructure. These limitations seem to explain the situation in Thai space technological development as well. The country has not been able to concretize any space-oriented innovation, regardless of the fact that the National Astronomical Research Institute has the vision to be a world-renowned organization in astronomy, technology, and innovation. This research investigated the struggles of Thailand in the space economy as a case study of deep technological development in middle-income states. With the rise of telecommunication that facilitates distance learning, the study utilized online-class as a method to eliminate the limitation of insufficient knowledge and further investigate other constraints. The findings indicate that online lessons effectively respond to the lack of space-related knowledge. Additionally, a financial concern of having hands-on experiences in deep technology is diminished by the curricular design that is built from the understanding of local context. However, online learning addresses a new communication issue. The absence of a communication platform that leads to a low rate of peer discussion, especially after lessons, becomes the main obstacle to nourish R & D. The study suggests that communication infrastructure is a key element to instigate inspiration and implementation of knowledge in practice. This can be mutually supported by course-content providers and state authorities.

  • Open access
  • 99 Reads
A Study of Lightweight Dynamic Algorithm of Power Management System for Small Satellite Applications
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This paper proposes the study of the lightweight dynamic algorithm of a power management for a small LEO-orbit satellite application such as CubeSat. The proposed work was designed in connection with a rule-based decision method and real-time scheduling. Here, the functional payloads of the satellite tasks were considered consisting of an electric power unit, attitude controller module, and environmental space system. The main system functions of the satellite operation were scheduled at the work process and the scheduling of the mission tasks were based on decision-making rules. It shows that the lightweight dynamic algorithm was aimed to optimize the efficiency and performance. The study of the proposed work was based on a simulation to understand the energy behavior and also consider the task priority.

The novel dynamic algorithm was proposed in order to deal with the power condition and distribution modules. It allows the strategy of a power management depending on a linear decision rule approach. The factors of power management consist of a design of the state of charge (SoC) of batteries and the consumption characteristics of the payload satellite interfaces. The energy profile was modeled according to the LEO operation based on the orbital period. The satellite payloads were concerned energy budgets including a telecommunication, attitude controller and functional loads in action. As a result, the efficiency and performance of battery can contribute to the lifespan of a satellite, and also design of a miniaturized satellite.

  • Open access
  • 95 Reads
Research on magnetic field homogenous analysis through Helmholtz coil mechanism for Ground-based Attitude Determination and Control testing platform
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A desired orientation in outer space, with a specified level of precision, is a mission requirement for every spacecraft based-on payload condition. Technically, Attitude Determination and Control Sub-system (ADCS) is responsible for satisfying this requirement which primary focused on Low-Earth Orbit small satellite missions. To make the analysis realistic, ground-based ADCS simulation and testing platform was established under Thai Space Consortium (TSC) program at National Astronomical Research Institute of Thailand, Chiang-Mai, Thailand. Normally, the Helmholtz coil is a primary equipment to simulate the Earth’s magnetic field that is a part of ADCS. In this research, the Biot Savart’ s Law was applied to describe the magnetic distribution through the mechanism of Helmholtz coil (circular and square) based on International Geomagnetic Reference Field model in three-axis. The facility’s objective is testing and verification of the TSC’s small satellite research and developing program. Therefore, in this paper, we introduce hardware-in-the-loop test bench with specific devices, their performances, and future extensions in progress.

  • Open access
  • 90 Reads
Multiple-Unmanned Air Vehicle Trajectory Optimization during Close-Approach Boundary based on Line-of-Sight Technique

The rendezvous mission is one of the most useful and interesting in aerospace industry. Working together of multiple Unmanned Aerial Vehicles (UAV)s with limited space can cause the damage to UAVs. This research presents Unmanned Aerial Vehicle (UAV) rendezvous method that can approach UAV to another UAV with minimum displacement between them while they are moving. This rendezvous method is guided by Line-of-Sight (LOS) guidance law. The mission is guiding the UAV to join the route of another UAV to the end of mission with minimum displacement and without collision between them. Aerial Information and Robotics Simulation or AirSim which is working on Unreal Engine 4 software is presented. The positioning of UAVs is provided by Global Positioning System (GPS) sensor on both UAVs.

  • Open access
  • 57 Reads
Reduction of Rocket Dispersion Using Model Predictive Lateral Pulse Jet Control

Uncontrolled fire ground to ground rockets produce high impact point dispersion due to various sources of error and environmental uncertainties. To increase a high single-shot hit probability, the rocket systems must equip with an on-board control mechanism. This paper investigates the use of lateral pulse jet control to reduce the dispersion of fire rockets. The numerical simulation of rocket trajectory is used to predict the impact point from an arbitrary state. The magnitude and direction of pulse jet thrust are based on the difference between the predicted impact point and target location. A comparison of dispersion for the uncontrolled and controlled impact points is proceeded through a Monte-Carlo simulation. It is shown that the dispersion radius, which is defined as the radius of circle centered at the mean impact point and containing 50% of the impact points, for the controlled case is noticeably smaller than the uncontrolled case.

  • Open access
  • 83 Reads
Effects of Space Debris Collision on 5-Bar Linkage Robot Operation in Satellites: Simulation Approach
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One of the most common damages of satellites is occurred by collisions of space debris. The collision of the debris is unavoidable during the space operation; therefore, the study of physical effects in relation to the collision must be conducted in order to understand the consequences. This article focuses on the analysis of the predictability of a robot arm A 5-bar planar robot with PID controller, that works inside the satellite. The analysis is performed by a simulation approach. The relationship between satellite damage and the debris’ size and speed, which vary according to the altitude, is analyzed. Consequently, the designs of small satellites’ orbits can be improved by using this study. As a result, the final condition of an operational satellite structure against a collision of valuable space debris can be predicted. Due to the motion control, the robot’s maximum position error is xx cm. This study leads to future work where the design rules for reducing the effect of payload variability will be developed.

  • Open access
  • 41 Reads
Developed a noiseless air inflator to increase the efficiency of testing robots in 2-dimensional zero gravity

Space programs and space technology that arise today are highly valued and important in the development of the Earth, showing the complexity and difficulty of creating or operating goals. If there is a system failure or problem beyond expectation, the damage could cause the space program to be suspended, or even the astronauts have fatal injuries. Therefore, the system must be tested as much as possible. Research has demonstrated the development of a mobile robot for testing in microgravity and low-gravity environment on earth. Compared to conventional systems based on the amount of air loaded on a mobile robot represents a duration of testing per cycle. We developed an inflation system by building another mobile robot to inflate it so that the test system can be tested forever. Our research discusses investigating a preliminary inflation system by constructing air nozzles and inflators and testing docking on XY-table. We were interested in the effect of force effects in all directions on a mobile robot in microgravity and low-gravity being tested to develop a docking algorithm with the most negligible impact or none.

  • Open access
  • 60 Reads
Elimination of Microorganisms from Airflow Out of Air Conditioner Using Ozone Generating System
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Under hot weather condition, air conditioner is an important household device which control temperature and humidity of a closed chamber. A filtration in the air conditioner has functions in reducing dust and microorganisms of inlet airflow. However, humidity in conditioner system may enhance microbial growth inside the device and re-distribution in flowing out air. Furthermore, airborne pathogens are being concern because of epidermic crisis. In this research work, we investigated the impact of ozone, an air cleaning system, on reducing microorganism quality and quantity of airflow out of the conditioner. The ozone generating system is constructed and cooperated over the airflow channel. This ozone system is opened for fifteen minutes before placing enrich media at five different positions of pre-conditioning room. The medium plates were opened for fifteen minutes at 0, 3, 6, 12 and 24 hours after generating ozone. Collecting plates were incubated at room temperature and counted the microorganism colony for four days. The result showed that ozone generator cooperated over airflow out of the conditioner evidently presented a smaller number of microorganisms (bacteria, yeast, and fungi) in compared to non-cooperated system did. Therefore, the cooperated ozone treatment is effectiveness in eliminating microorganisms in the air conditioning room.

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