Low-Cost and Reliable Ground Station Network to Improve Operation Efficiency for Micro/Nano-Satellites
- Paper number
IAC-05-D1.4.06
- Author
Dr. Yuya Nakamura, University of Tokyo, Japan
- Coauthor
Mr. Yasuhisa Oda, University of Tokyo, Japan
- Coauthor
Prof. Shinichi Nakasuka, University of Tokyo, Japan
- Year
2005
- Abstract
Microbiological monitoring of air and surfaces within the ISS indicated that bacteria of the genus Staphylococcus are found with high frequency. Staphylococcus aureus, an opportunistic pathogen with the capacity to cause severe debilitating infection, constitutes a significant proportion of these isolates. Ground-based studies of Salmonella enterica have provided evidence that bacterial virulence is increased under the influence of simulated microgravity. These studies, and others linking space flight to reduced immune competence, provide clear evidence that extended missions may be compromised by increased risk of infection. We have therefore examined the effects of simulated microgravity on the virulence properties of S. aureus. The methicillin-susceptible S. aureus isolates RF1, RF6 and RF11 were grown in a Synthecon High Aspect Ratio Vessel (HARV) under low shear modelled microgravity (LSMMG) and compared with cells grown under normal gravity (NG). Global gene expression was determined by DNA microarray analysis and protein secretion examined using two-dimensional gel electrophoresis. Growth in a modelled microgravity environment had an impact on a number of factors associated with the virulence of S. aureus. LSMMG elicited large reductions in protein secretion by the three isolates; in particular isolate RF6 displayed a four-fold reduction in protein secretion. In total, 40 proteins were found to be down-regulated under LSMMG in a highly reproducible fashion. LC-MS/MS identified these proteins to be involved mainly with cell metabolism, including protein biosynthesis, folding and transport; 4 proteins were also found to be iron-binding proteins. DNA microarray identified significant changes in gene regulation; these were in the main associated with cell metabolism, transport, stress and virulence. For isolate RF6, the expression of a major virulence gene, hla, and the virulence regulatory system saeR/ saeS was found to be reduced two-fold. These data provide strong evidence that growth of S. aureus under modelled microgravity leads to a reduction in expression of virulence determinants.
University of Tokyo and Tokyo Institute of Technology succeeded in launching their CubeSats in June 2003, named "CubeSat XI-IV" and "CUTE-I" respectively. This was the first launch of CubeSats by universities in the world, and these two nano-satellites have been working perfectly in orbit for over 1.5 years, which surprised many space-related people. Now many facilities all over the world are accelerating or newly beginning their own micro/nano-satellite development project. However through operation of our CubeSat, several technical problems have become apparent. beginitemize item Most university satellites utilize amateur band for communication, and the operation is often disturbed by illegal ham stations. item Visible time of the satellite per operation is around 20 minutes at longest, and the amount of obtained data is highly limited due to the low bit rate communication widely used for ham radio. enditemize
University of Tokyo enlisted cooperation from ham operators in different parts of Japan to improve the data acquisition efficiency from CubeSat XI-IV. They connect to our ground station server through the Internet, and send data they received at their own station to us in real time. By introducing this system, the average data amount per operation doubled. This result indicates that the cooperation of many ground stations would improve operation efficiency.
Japanese universities developing micro/nano-satellites initiated the Ground Station Network (GSN) project. This project aims for remote satellite operation by connecting distributed ground stations via the Internet. This GSN system realizes operations with longer visible time by utilizing multiple stations (if uplink from remote stations is legal), as well as the aforementioned merits of improving data acquisition rate. For example, visible time for 15 minutes with normal operation in Tokyo can be extended up to around 30 minutes if stations in Hokkaido and Okinawa cooperate using this GSN system. On the condition that ground stations around the world can work together, it would be possible to realize the seamless operation.
However, the concept of ground station network itself is not nothing new. This system is already widely used in the professional field. The crucially different points from such system are as follows;
beginitemize item Use of the Internet, not dedicated lines for communication. Under the current status that the Internet is highly sophisticated and that every person can connect it so easily, it is natural choice to use the Internet as the communication method. In addition, we can establish low-cost, reliable and robust system. item Autonomous operation system. Once a user connects to the server from his/her terminal, the server will search the most appropriate ground station for the designated satellite operation from widely distributed stations. The selected station controls the equipment automatically, and received data is delivered to the user terminal. item Open architecture. The most important point here is that what we are trying to provide is NOT software itself. GS equipment such as a transceiver varies depending on each station, and this makes it difficult to provide the unified software. In this project, we place an emphasis on establishing and providing the software specification, or protocol. Only every station has to do is to develop the equipment control software suitable for their own station following the open protocol, which will encourage the spread of GSN. item Open system to every organization. By establishing and providing open and easy-to-understand system framework, any organizations and universities can participate in the network. enditemize
We will introduce the current status of GSN project, clarify technical and legal issues, and make a demonstration if possible. We are going to encourage the participation in this GSN project of organizations all over the world on various occasions.
- Abstract document
- Manuscript document
IAC-05-D1.4.06.pdf (🔒 authorized access only).
To get the manuscript, please contact IAF Secretariat.