A versatile constellation of microsatellites with electric propulsion for Earth Observation: mission analysis and platform design

The increasing interest towards the exploitation of the observations from the space to support daily human activities devoted to land and vegetation management is the starting point for the creation of Earth Observation missions. Actual state-of-art technology and future perspectives allow to think to design a very small platform able to be equipped with an instrument devoted to satisfy requirements imposed by all possible involved users. This thesis describes the mission analysis related to a constellation of microsatellites which seems an optimum solution to achieve with limited costs the very high performance demanded by applications for natural resources management, like for example agriculture or disasters monitoring. The presence of a micro-electric propulsion device on-board the platform like the ALTA HT100D is studied. This unique feature of the mission provides an excellent degree of versatility, ensuring a further reduction of costs and increase of performance. Different mission scenarios are proposed, and a preliminary design of the platform is provided

Nanosatellite Store-and-Forward Communication Systems for Remote Data Collection Applications

Due to compact design, cost-effectiveness and shorter development time, a nanosatellite constellation is seen as a viable space-based data-relay asset to collect data from remote places that are rather impractical to be linked by terrestrial means. While nanosatellites have these advantages, they have more inherent technical limitations because of limited space for subsystems and payloads. Nanosatellite S&F communication systems are notably challenging in this respect due to requirements on antennas, transceivers, and signal processing. Although nanosatellites can be scaled up for better resources and capabilities, smaller platforms (i.e., ≤6U CubeSat) tend to be used for cost-effectiveness and lower risk. This thesis dealt with the problem of designing a nanosatellite S&F communication system for delay-tolerant remote data collection applications considering: (a) technical constraints in hardware, processing capabilities, energy budget and space in both the nanosatellite and ground sensor terminal (GST) sides; (b) physical communication layer characteristics and constraints such as limited available bandwidth, LEO channel Doppler, attenuation and fading/shadowing effects, low transmit power and data rate, and multi-user interference among asynchronously transmitting terminals. We designed, developed, and operated an amateur radio payload with S&F communication and APRS-DP capabilities, and performed a post-launch communication failure investigation. We also investigated suitability of E-SSA protocol for IoT/M2M terminals to nanosatellite communication by analyzing performance and energy efficiency metrics. The thesis comprises nine chapters. Chapter 1 describes the research background, problem, objectives, state of research, potential contributions of this thesis, and a gist of methodology detailed in later chapters. Chapter 2 and 3 provide an extensive literature review. Chapter 2 reviews the previous research works on using nanosatellites for S&F communication for remote data collection, and the previous nanosatellite S&F missions. Such research works and nanosatellite missions were undertaken primarily in the context of non-commercial/civil applications. Then, Chapter 2 surveys the recent commercial nanosatellite IoT/M2M players and examines their proposed systems in terms of satellite platform, constellation design, communication technology, targeted applications, requirements, and performance. Chapter 3 presents a literature review on communication system architecture, physical layer and random-access schemes, protocols, and technologies relevant to satellite IoT/M2M systems. In the context of IoT/M2M applications, the constraints in energy budget, transmit power and available bandwidth limit the system’s capacity in terms of amount of data that can be received and number of GSTs that can be supported. In both nanosatellite and GST sides, there are stringent limitations in hardware complexity, processing capabilities and energy budget. Addressing these challenges requires a simple, spectrally and energy efficient asynchronous random-access communication protocol. This research investigated using the enhanced spread spectrum Aloha (E-SSA) protocol for satellite IoT/M2M uplink (terminal to satellite) communication and analyzed its performance and suitability for the said application. Chapter 4 discusses the BIRDS-2 CubeSat S&F remote data collection system, payload design, development, tests, and integration with the BIRDS-2 CubeSats. Chapter 5 discusses the investigation on communication design issues of BIRDS-2 CubeSat S&F payload, tackling both the methodology and findings of investigation. It is noted that there are only a few satellites that have carried an APRS-DP payload but even some of these failed due to communication, power, or software issues. In BIRDS-2 Project, considering tight constraints in a 1U CubeSat equipped with other subsystems and payloads, we developed a S&F/APRS-DP payload and integrated it with each of the three 1U CubeSats of participating countries. After launching the CubeSats from the ISS, several amateur operators confirmed reception downlink beacon messages, but full two-way communication failed due to uplink communication failure. Thus, this research not only studied the design and development of a S&F/APRS-DP payload suitable for a CubeSat platform, but also systematically investigated the causes of communication failure by on-orbit observation results and ground-based tests. We found that uplink failure was caused by two design problems that were overlooked during development, namely, the poor antenna performance and increased payload receiver noise floor due to satellite-radiated EMI coupled to the antenna. Chapter 6 first describes the enhanced spread spectrum Aloha (E-SSA) based nanosatellite IoT/M2M communication model implemented in Matlab and derives the mathematical definitions of packet loss rate (PLR), throughput (THR) and energy efficiency (EE) metrics. Then, it tackles the formulated baseband signal processing algorithm for E-SSA, including packet detection, channel estimation, demodulation and decoding. Chapter 7 presents the simulation results and discussion for Chapter 6. Chapter 8 tackles the S&F nanosatellite constellation design for global coverage and presents the results and findings. Chapter 9 describes the laboratory setups for validating the E-SSA protocol and then presents the findings. Finally, Chapter 9 also gives the summary, conclusions, and recommendations. Simulation results showed that for E-SSA protocol with the formulated algorithm, THR, PLR and EE metrics are more sensitive to MAC load G, received power variation σLN and Eb/N0, due to imperfect detection and channel estimation. With loose power control (σLN=3dB), at Eb/N0=14 dB, the system can be operated up to a maximum load of 1.3 bps/Hz, achieving a maximum THR of 1.25 bps/Hz with PLR<0.03. Without power control (σLN=6dB,9dB), at Eb/N0=14 dB, maximum load is also 1.3 bps/Hz, but achievable THR is lower than ~1 bps/Hz and PLR values can be as high as ~0.23. Worse PLR results are attributed to misdetection of lower power packets and demodulation/decoding errors. Both are caused by the combined effects of MUI, channel estimation errors, imperfect interference cancellation residue power, and noise. The PLR and THR can be improved by operating with higher Eb/N0 at the expense of lower energy efficiency. Then, laboratory validation experiments using a SDR-based platform confirmed that with G=0.1, Eb/N0=14dB, σLN=6dB, the formulated algorithm for E-SSA protocol can still work even with inaccurate oscillator (±2 ppm) at GSTs, obtaining experimental PLR result of 0.0650 compared to simulation result of 0.0352. However, this requires lowering the detection thresholds and takes significantly longer processing time. For the S&F nanosatellite constellation design, it was found that to achieve the target percent coverage time (PCT) of more than 95% across all latitudes, a 9x10 Hybrid constellation or a 10x10 Walker Delta constellation would be required.九州工業大学博士学位論文 学位記番号：工博甲第506号 学位授与年月日：令和2年9月25日1: Introduction|2: Nanosatellite S&F Research, Missions and Applications|3: Satellite S&F Communication Systems and Protocols|4: BIRDS-2 CubeSat S&F Data Collection System, Payload Design and Development|5: Investigation on Communication Design Issues of BIRDS-2 CubeSat APRS-DP/S&F Payload, Results and Discussion|6: E-SSA-based Nanosatellite IoT/M2M Communication System Model and Signal Processing Algorithm|7: Simulation Results and Discussion for E-SSA-based Nanosatellite IoT/M2M Communication System|8: Nanosatellite Constellation for Global Coverage|9: Experimental Laboratory Validation for E-SSA Protocol, Research Summary, Conclusions and Recommendations九州工業大学令和2年

Small-Satellite Mission Failure Rates

The purpose of this report is to determine the failure rate of small-satellite missions launched between the years 2000 and 2016. This analysis considers the rates of both partial and total mission failure, as well as the failures attributable to failure of the launch vehicle. This study observed that between the years of 2000 to 2016, 41.3% of all small satellites launched failed or partially failed. Of these small satellite missions, 24.2% were total mission failures, another 11% were partial mission failures, and 6.1% were launch vehicle failures. The small satellite failure data reveals an increase in the failure rate as the yearly launch rate has increased. The period 2000 to 2008 averaged 15 launches per year, during which 28.6% of the small satellite missions failed or partially failed. The period from 2009 to 2016 averaged 48 launches per year, during which 42.6% of the small satellite missions failed or partially failed. The launch vehicle failure rate for both periods was the same at around 6.1%. The implication is that for modern small satellite missions, almost one out of every two small satellite missions will result in either a total or a partial mission failure. Counting the partial mission successes as successful missions reduces the failure rate, but only to 38.2% for the period 2009 to 2016

Space micropropulsion systems for Cubesats and small satellites: From proximate targets to furthermost frontiers

Rapid evolution of miniaturized, automatic, robotized, function-centered devices has redefined space technology, bringing closer the realization of most ambitious interplanetary missions and intense near-Earth space exploration. Small unmanned satellites and probes are now being launched in hundreds at a time, resurrecting a dream of satellite constellations, i.e., wide, all-covering networks of small satellites capable of forming universal multifunctional, intelligent platforms for global communication, navigation, ubiquitous data mining, Earth observation, and many other functions, which was once doomed by the extraordinary cost of such systems. The ingression of novel nanostructured materials provided a solid base that enabled the advancement of these affordable systems in aspects of power, instrumentation, and communication. However, absence of efficient and reliable thrust systems with the capacity to support precise maneuvering of small satellites and CubeSats over long periods of deployment remains a real stumbling block both for the deployment of large satellite systems and for further exploration of deep space using a new generation of spacecraft. The last few years have seen tremendous global efforts to develop various miniaturized space thrusters, with great success stories. Yet, there are critical challenges that still face the space technology. These have been outlined at an inaugural International Workshop on Micropropulsion and Cubesats, MPCS-2017, a joint effort between Plasma Sources and Application Centre/Space Propulsion Centre (Singapore) and the Micropropulsion and Nanotechnology Lab, the G. Washington University (USA) devoted to miniaturized space propulsion systems, and hosted by CNR-Nanotec - P.Las.M.I. lab in Bari, Italy. This focused review aims to highlight the most promising developments reported at MPCS-2017 by leading world-reputed experts in miniaturized space propulsion systems. Recent advances in several major types of small thrusters including Hall thrusters, ion engines, helicon, and vacuum arc devices are presented, and trends and perspectives are outlined.This work was supported in part by the following funds and organizations: OSTIn-SRP/EDB through National Research Foundation and in part by MoE AcRF (Rp6/16 Xs), Singapore; National Natural Science Foundation of China (Grant Nos. 51777045 and 51477035); National Technical Basic Scientific Research of China, Grant No. JSZL2016203c006; NASA DC Space Grant Consortium; Grant-in-Aid for Scientific Research under Grant S: 21226019 and Grant B: 17H02295 through the Japan Society for the Promotion of Science, and by NIFS budget code NIFS17KLER063, and KAKENHI grant: Grant-in-Aid for Scientific Research (S), No. JP16H06370; S.S. thanks late Professor K. Toki, late Dr. K. P. Shamrai, Dr. Kuwahara, and the HEAT project members for their contribution Y.R. acknowledges the support from the US DOE under Contract No. DE-AC02-09CH11466; I.L. acknowledges the support from the School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology; special thanks to L. Xu, M. Lim, S. Huang, and the entire PSAC/SPCS for their help

Satellite based synthetic aperture radar and optical spatial-temporal information as aid for operational and environmental mine monitoring

A sustainable society is a society that satisfies its resource requirements without endangering the sustainability of these resources. The mineral endowment on the African continent is estimated to be the first or second largest of world reserves. Therefore, it is recognised that the African continent still heavily depends on mineral exports as a key contributor to the gross domestic product (GDP) of various countries. These mining activities, however, do introduce primary and secondary environmental degradation factors. They attract communities to these mining areas, light and heavy industrial establishments occur, giving rise to artisanal activities. This study focussed on satellite RS products as an aid to a mine’s operations and the monitoring of its environment. Effective operational mine management and control ensures a more sustainable and profitable lifecycle for mines. Satellite based RS holds the potential to observe the mine and its surrounding areas at high temporal intervals, different spectral wavelengths and spatial resolutions. The combination of SAR and optical information creates a spatial platform to observe and measure the mine’s operations and the behaviour of specific land cover and land use classes over time and contributes to a better understanding of the mining activities and their influence on the environment within a specific geographical area. This study will introduce an integrated methodology to collect, process and analyse spatial information over a specific targeted mine. This methodology utilises a medium resolution land cover base map, derived from Landsat 8, to understand the predominant land cover types of the surrounding area. Using very high resolution mono- and stereoscopic satellite imagery provides a finer scale analysis and identifies changes in features at a smaller scale. Combining these technologies with the synthetic aperture radar (SAR) applications for precise measurement of surface subsidence or upliftment becomes a spatial toolbox for mine management. This study examines a combination of satellite remote sensing products guided by a systematic workflow methodology to integrate spatial results as an aid for mining operations and environmental monitoring. Some of the results that can be highlighted is the successful land cover classification using the Landsat 8 satellite. The land cover that dominated the Kolomela mine area was the “SHRUBLAND/GRASS” class with a 94% coverage and “MINE” class of 2.6%. Sishen mine had a similar dominated land cover characteristic with a “SHRUBLAND/GRASS” class of 90% and “MINE” class of 4.8%. The Pléiades time-series classification analysis was done using three scenes each acquired at a different time interval. The Sishen and Kolomela mine showed especially changes from the bare soil class to the asphalt or mine class. The Pléiades stereoscopic analysis provided volumetric change detection over small, medium, large and recessed areas. Both the Sishen and Kolomela mines demonstrated height profile changes in each selected category. The last category of results focused on the SAR technology to measure within millimetre accuracy the subsidence and upliftment behaviour of surface areas over time. The Royal Bafokeng Platinum tailings pond area was measured using 74 TerraSAR-X scenes. The tailings wall area was confirmed as stable with natural subsidence that occurred in its surrounding area due to seasonal changes of the soil during rainy and dry periods. The Chuquicamata mine as a large open pit copper mine area was analysed using 52 TerraSAR-X scenes. The analysis demonstrated significant vertical surface movement over some of the dumping sites. It is the wish of the researcher that this dissertation and future research scholars will continue to contribute in this scientific field. These contributions can only assist the mining sector to continuously improve its mining operations as well as its monitoring of the primary as well as the secondary environmental impacts to ensure improved sustainability for the next generation.Environmental SciencesM. Sc. (Environmental Science

State of the Art: Small Spacecraft Technology

This report provides an overview of the current state-of-the-art of small spacecraft technology, with particular emphasis placed on the state-of-the-art of CubeSat-related technology. It was first commissioned by NASAs Small Spacecraft Technology Program (SSTP) in mid-2013 in response to the rapid growth in interest in using small spacecraft for many types of missions in Earth orbit and beyond, and was revised in mid-2015 and 2018. This work was funded by the Space Technology Mission Directorate (STMD). For the sake of this assessment, small spacecraft are defined to be spacecraft with a mass less than 180 kg. This report provides a summary of the state-of-the-art for each of the following small spacecraft technology domains: Complete Spacecraft, Power, Propulsion, Guidance Navigation and Control, Structures, Materials and Mechanisms, Thermal Control, Command and Data Handling, Communications, Integration, Launch and Deployment, Ground Data Systems and Operations, and Passive Deorbit Devices

Regulating a revolution : small satellites and the law of outer space

Chapter 1 of the study includes introduction to small satellites activities, it explains and explores what are small satellites, what applications such satellites support, and introduces important terminology. Chapter 2 summarises and analyses the applicability of the existing treaty law to small satellites operations, as well as recent discussions and developments in international bodies such as UN COPUOS and the ITU with respect to international regulation of small satellites activities. Chapter 3 includes a deep legal analysis of State responsibility for non-governmental small satellites activities. It refers to Article VI of the Outer Space Treaty as well to basic concepts as “nationality” in general international law. It analyses case studies which illustrates the legal challenges relating to the application of Article VI in the context of small satellites. Chapter 4 focuses on analysing the applicability of the Liability Convention in relation to small satellites, especially with respect to “fault liability” in outer space. Chapter 5 addresses the legal concept of registration of space objects in the space treaties, and “jurisdiction and control”. It analyses the problematic legal relations between State responsibility, the liability of the launching State and the ability of the latter to exercise jurisdiction and control as the State of registry, in the case of non-governmental small satellites. Chapter 6 summarises the findings of the study and includes analogies to cases where justification to treat certain small scale activities in a special manner was found, referring to the de minimis doctrine. It further includes recommendations and a concrete solution to deal with the legal difficulties which were identified, namely, a draft Optional Protocol to the Outer Space Treaty, aimed to supplement the treaty and internationally regulate non-governmental small satellites activities in more detail.Exploring the Frontiers of International La

Factors Influencing Customer Satisfaction towards E-shopping in Malaysia

Online shopping or e-shopping has changed the world of business and quite a few people have decided to work with these features. What their primary concerns precisely and the responses from the globalisation are the competency of incorporation while doing their businesses. E-shopping has also increased substantially in Malaysia in recent years. The rapid increase in the e-commerce industry in Malaysia has created the demand to emphasize on how to increase customer satisfaction while operating in the e-retailing environment. It is very important that customers are satisfied with the website, or else, they would not return. Therefore, a crucial fact to look into is that companies must ensure that their customers are satisfied with their purchases that are really essential from the ecommerce’s point of view. With is in mind, this study aimed at investigating customer satisfaction towards e-shopping in Malaysia. A total of 400 questionnaires were distributed among students randomly selected from various public and private universities located within Klang valley area. Total 369 questionnaires were returned, out of which 341 questionnaires were found usable for further analysis. Finally, SEM was employed to test the hypotheses. This study found that customer satisfaction towards e-shopping in Malaysia is to a great extent influenced by ease of use, trust, design of the website, online security and e-service quality. Finally, recommendations and future study direction is provided. Keywords: E-shopping, Customer satisfaction, Trust, Online security, E-service quality, Malaysia