FPGA-based operational concept and payload data processing for the Flying Laptop satellite

Flying Laptop is the first small satellite developed by the Institute of Space Systems at the Universität Stuttgart. It is a test bed for an on-board computer with a reconfigurable, redundant and self-controlling high computational ability based on the field pro- grammable gate arrays (FPGAs). This Technical Note presents the operational concept and the on-board payload data processing of the satellite. The designed operational concept of Flying Laptop enables the achievement of mission goals such as technical demonstration, scientific Earth observation, and the payload data processing methods. All these capabilities expand its scientific usage and enable new possibilities for real-time applications. Its hierarchical architecture of the operational modes of subsys- tems and modules are developed in a state-machine diagram and tested by means of MathWorks Simulink-/Stateflow Toolbox. Furthermore, the concept of the on-board payload data processing and its implementation and possible applications are described

In-orbit Demonstration of Reaction Control System for Orbital Altitude Change of Micro-Satellite ALE-2

This research presents the results of an in-orbit test of the orbital altitude control for a micro-satellite equipped with the first space-demonstrated high-density small cold gas jet thruster. In the field of micro-satellites, the application of thrusters to practical missions has not yet progressed due to their high cost, mechanical and electrical incompatibility with the satellite bus system, and increased operational risks. By contrast, the demand for orbit control functions has been increasing in recent years with the expansion of micro-satellite applications. The76kg satellite ALE-2 , which was jointly developed by Tohoku University and ALE Co., Ltd., has the world\u27s first challenging mission to artificially generate shooting stars by ejecting small substances (meteor source) from the ejection device fixed on the satellite body. To avoid collision of the ejected meteor source with other flying objects, the mission must be performed in a sun-synchronous orbit at an altitude of less than 400 km, which is lower than that of the International Space Station. However, it is required to maintain the mission orbit autonomously because the orbit decay is large due to the effect of atmospheric drag. In addition, to release the meteor source at an arbitrary orbital position, it is essential to manipulate the ground track by raising and lowering the orbital altitude. Therefore, ALE-2 needs to control the orbit altitude actively and with arbitrary amount of change. In this study, the reaction control system (RCS), which satisfies the orbit change capability, mission requirements, and compatibility with the satellite bus system, is installed on ALE-2 to perform space demonstrations of orbit control and to evaluate the operational performance of the thruster. ALE-2 will be the first to be equipped with a cold gas jet thruster developed by Patched conics, LLC. It is estimated that the thruster is capable of changing altitude more than 1 km by continuous drive for one orbital period. Using this RCS, the following three criteria were set as the evaluation criteria: (Minimum) the orbit altitude can be actively changed by the thruster, (Full) the orbit altitude can be controlled by an arbitrary amount of operation and can be increased more than 1 km per orbit, and (Extra) the mission orbit can be transferred according to the meteor source release plan. ALE-2 was launched on December 6, 2019, and the in-orbit test of the RCS started four months later. Although the RCS was not able to achieve its initial orbit change capability due to an anomaly in the power supply system, various kinds of tests were conducted under conditions that allowed continuous thruster operation. It was confirmed that the orbit altitude was increased by 0.4 km per orbit. In addition, the fault detection, isolation and recovery (FDIR)function was effectively performed against any kinds of anomalies of RCS during in-orbit operation. Therefore, a sustained orbital altitude of 400 km was expected to be achievable using the onboard RCS

Statistical Analysis of Lessons Learned from University Satellite Projects in Japan

University Space Engineering Consortium (UNISEC) is a non-profitable organization established in 2003 with the purpose of supporting the “ realization of practical space engineering activities, ” and providing support to universities and research institutions in Japan. UNISEC has accumulated practical experiences and achievements from more than 80 micro- and nano-satellite projects of the corporate partners, which also includes the two world-first-CubeSats launched in 2003. Following the recent drastic increase of academic and commercial space development and utilization activities all over the world, UNISEC has recently conducted a survey on the lessons learned of safety and mission assurance of these satellites partly as a contract from JAXA, to distill the best practices to ensure the mission success of the satellites. The survey contains replies from more than 15 faculty members and researchers of 10 universities or institutions or colleges with information about 36 satellite projects, 208 individual success and failure cases. In this research, we analyzed questionnaires of lessons learned from each satellite project statistically by sampling specific terms and counting frequency. The questionnaire contains technical topics and project management topics (including human factors, team/organization factors, schedule factors) for the analysis of individual subjects of success or failure. The examples are categorized into the following: Accomplishments or failures of the mission on orbit, Demonstrations or troubles on the bus functions, and Supplemental products (design/test process, educational effects)

Development of an Operating Strategy for On-Demand Earth Observation Missions of the Diwata-2 Microsatellite

Diwata-2 is the Philippines’ 2nd microsatellite developed by Tohoku University, Hokkaido University, University of the Philippines, and the Philippine Department of Science and Technology. Its primary purpose is gathering remote sensing data through imaging areas of interest for the Philippines. This paper presents the study of Diwata-2’s initial Earth observation pointing performance, investigation of its Attitude Determination and Control System, the tuning of its Star Tracker sensor parameters, the in-flight target pointing calibration, and the sequential scheduling of its components forming an operation strategy for an effective on-demand earth observation mission. This operation strategy has managed to improve the satellite’s pointing performance from the initial 2.88°±2.06° RMS pointing error to having an accuracy of 0.204°±0.12° RMS for its High Precision Telescope payload. This strategy has been implemented to the university-built microsatellite for over 400 successful Earth observation missions and has covered about 82.8% of the Philippine’s land area with its Spaceborne Multispectral Imager payload

Bmi1 regulates memory CD4 T cell survival via repression of the Noxa gene

The maintenance of memory T cells is central to the establishment of immunological memory, although molecular details of the process are poorly understood. In the absence of the polycomb group (PcG) gene Bmi1, the number of memory CD4+ T helper (Th)1/Th2 cells was reduced significantly. Enhanced cell death of Bmi1−/− memory Th2 cells was observed both in vivo and in vitro. Among various proapoptotic genes that are regulated by Bmi1, the expression of proapoptotic BH3-only protein Noxa was increased in Bmi1−/− effector Th1/Th2 cells. The generation of memory Th2 cells was restored by the deletion of Noxa, but not by Ink4a and Arf. Direct binding of Bmi1 to the Noxa gene locus was accompanied by histone H3-K27 methylation. The recruitment of other PcG gene products and Dnmt1 to the Noxa gene was highly dependent on the expression of Bmi1. In addition, Bmi1 was required for DNA CpG methylation of the Noxa gene. Moreover, memory Th2-dependent airway inflammation was attenuated substantially in the absence of Bmi1. Thus, Bmi1 controls memory CD4+ Th1/Th2 cell survival and function through the direct repression of the Noxa gene