Issue Small Satellites

Small satellite is a disruptive technology in space industries. Traditionally, space industries were dominated by satellites which have thousands of kilograms and are bulky and expensive. Small satellites denote a new generation of miniaturized satellites which, by taking advantages of modern technologies (e.g., integrated circuits, digital signal processing, MEMS, and additive manufacturing), can achieve a significant reduction in volume, mass, development time, and cost of satellites. During recent decades, small satellites, including CubeSats, NanoSats, MiniSats, and MicroSats, have undergone rapid developments, and are playing an increasingly larger role in exploration, technology demonstration, scientific research, and education. These miniature satellites provide a low-cost platform for missions, including planetary space exploration, Earth observations, fundamental Earth and space science, and developing precursor science instruments like laser communications and millimeter-wave communications for intersatellite and intrasatellite links, and autonomous movement capabilities. They also allow educators an inexpensive means to engage students in all phases of satellite development, operation, and exploitation through real-world, hands-on research and development experience on rideshare launch opportunities. A number of miniaturized satellites can form spaceborne wireless sensor networks in the space, which are also going to play an important role in Internet of Space (IoS) of the futur

低軌道のキューブサットからの原子時計ベースのUHF基準信号の時間差検出

Communication between the on-orbit satellite and ground station (GS) is highly affected by several factors, which result mainly on the delay and error. Satellite signal delay and error are especially depending on the amount of ionosphere Total Electron Content (TEC) in the signal path. While the information of the TEC is currently available, the measurement of TEC has been mostly done using Global Navigation Satellite System (GNSS) signal and in some regions, the ionosonde data is also used. However, GNSSs are orbiting at altitude more than 20,000 Km, and its main purpose is serving as the navigation. Signals from a satellite orbiting in lower altitude with lower frequencies than GNSS may provide more precise measurement of TEC. Space Precision Atomic Clock Timing Utility Mission (SPATIUM) is a project to do three-dimensional ionosphere mapping by a satellite constellation in LEO measuring TEC with the Ultra High Frequency (UHF) radio signals. The first technology demonstration satellite called SPATIUM-I, a 2U CubeSat, was deployed from International Space Station in October 2018. The satellite emits 467MHz reference signal generated by a chip scale atomic clock. The signal is spread spectrum modulated with 250 chips in 4 msec. This thesis will present the development of the method to detect time difference between two consecutive signals received from the on-orbit SPATIUM-I satellite. The time difference will then be processed to derive the TEC difference between two locations. The time delay measurement will be done using commercially available Software Defined Radio (SDR) on ground station. However, the clock precision become the major challenge in the process, which leads to high error for the measurement. One of the methods to improve the clock is to inject the Global Positioning System (GPS) clock into the system. The key to this research is to be able to detect the beginning of the recovered spread spectrum chips using its I/Q data. For this purpose, signal processing using Matlab is done.九州工業大学博士学位論文 学位記番号: 工博甲第545号 学位授与年月日: 令和4年3月25日1 Introduction |2 Literature Review|3 Spatium-I Satellite Development|4 Time Difference Measurement|5 Spatium-I Signal Reception and Calculation for Tec Difference|6 Research Conclusion and Future Works九州工業大学令和3年

Combination of optical and SAR remote sensing data for wetland mapping and monitoring

Wetlands provide many services to the environment and humans. They play a pivotal role in water quality, climate change, as well as carbon and hydrological cycles. Wetlands are environmental health indicators because of their contributions to plant and animal habitats. While a large portion of Newfoundland and Labrador (NL) is covered by wetlands, no significant efforts had been conducted to identify and monitor these valuable environments when I initiated this project. At that time, there were only two small areas in NL that had been classified using basic Remote Sensing (RS) methods with low accuracies. There was an immediate need to develop new methods for conserving and managing these vital resources using up-to-date maps of wetland distributions. In this thesis, object- and pixel-based classification methods were compared to show the high potential of the former method when medium or high spatial resolution imagery were used to classify wetlands. The maps produced using several classification algorithms were also compared to select the optimum classifier for future experiments. Moreover, a novel Multiple Classifier System (MCS), which combined several algorithms, was proposed to increase the classification accuracy of complex and similar land covers, such as wetlands. Landsat-8 images captured in different months were also investigated to select the time, for which wetlands had the highest separability using the Random Forest (RF) algorithm. Additionally, various spectral, polarimetric, texture, and ratio features extracted from multi-source optical and Synthetic Aperture Radar (SAR) data were assessed to select the most effective features for discriminating wetland classes. The methods developed during this dissertation were validated in five study areas to show their effectiveness. Finally, in collaboration with a team, a website (http://nlwetlands.ca/) and a software package were developed (named the Advanced Remote Sensing Lab (ARSeL)) to automatically preprocess optical/SAR data and classify wetlands using advanced algorithms. In summary, the outputs of this work are promising and can be incorporated into future studies related to wetlands. The province can also benefit from the results in many ways

Prospettive per la regolamentazione dei piccoli satelliti nel diritto internazionale

The exploration and use of outer space is primarily realized through the use of artificial satellites around the Earth. Being realtively inexpensive to produce and easy to launch small satellites help to open the door to an indefinite number of actors, including developing countries and private entities. The first part of this research investigates the authorization framework of different space faring nations in order to point out how they incorporated in their national legislations specific provisions dedicated to small satellites’ missions. The objective is to identify which model is best suited to comply with obligations stemming from international treaties. However, the possibility of launching a huge number of satellites per year, because of their reduced cost and short production cycle is negatively affecting debris proliferation. Therefore in the second part of the research the concept of sustainable development and the extent of its role in interpreting States’ environmental obligations under international law is assessed. Then the meaning of long-term sustainability in outer space activities is further examined. Finally in light of the considerations provided, the specific threat posed by small satellites to the stability of the Low Earth orbit environment is analysed and some solutions are proposed