Space Communications

This paper has two purposes. One is to show what targets that satellite communications R&D for next 30 years should pursue. Another is to give a clear justification for a study of a geostationary platform. First, it discusses whether the satellite communications is needed or not in the IT (Information Technology) era. And it also discusses the necessity for satellite communications R&D, especially by the government. Second, the paper proposes a future vision of communications satellite R&D in response to the recent rapid increase of capacity of terrestrial links. Three generations of Internet satellite are proposed: first generation Internet satellite, in the 2000s; second generation Internet satellite in the 2010s; and third generation Internet satellite in 2020s, whose respective satellite capacities are several to several tens Gbps, several tens to several hundreds Gbps and several hundreds to several thousands Gbps. The first generation Internet satellite is based on R&D projects already approved in Japan. The second generation Internet satellite includes the technology for the more global scale of IT and higher speed communications. The third generation Internet satellite is a much more advanced system, for which it is necessary to introduce a future geostationary platform. Finally, it discusses the approach to technology R&D from the viewpoint that communications satellite R&D drives the high technology program. And the items of technology R&D are described.

In 1993, a proposal at the Japan–US Science, Technology, and Space Applications Program (JUSTSAP) workshop led to a subsequent series of satellite communications experiments and demonstrations, under the title of Trans‐Pacific High Data Rate Satellite Communications Experiments. The first phase of this was a joint collaboration between government and industry teams in the United States and Japan that successfully demonstrated distributed high definition video (HDV) post‐production on a global scale using a combination of high data rate satellites and terrestrial fiber optic asynchronous transfer mode (ATM) networks [1–3]. This was followed by the Phase‐2 Internet Protocol (IP) based experiments and demonstrations [4–7] in tele‐medicine and astronomical distance education, using another combination of two high data rate satellites and terrestrial fiber optic networks.

This paper describes the Phase‐2 remote astronomy experiment in detail. This experiment established a heterogeneous ground‐ and space‐based network between Japan and several sites in the US, which was used by students, scientists, and educators to provide real‐time interaction and collaboration with the 14‐inch Telescopes in Education (TIE) telescope and associated data archive.

The remote astronomy activity demonstrated collaborative observation and distance education at multiple locations around the globe and the transparent operations of distributed systems technologies over a combination of broadband satellites and terrestrial networks. The use of Internet Protocol related technologies allowed the general public to be an integral part of the exciting activities, helped to examine issues in constructing a global information infrastructure with broadband satellites, and afforded an opportunity to tap the research results from the (reliable) multicast and distributed systems communities.

In this paper, we describe the network infrastructure at both the technical and user levels, review the operation of the experiment, and summarize our lessons learned. We find that such networking, while still somewhat complex to construct on highly distributed scales, can provide educators and students with a unique collaborative environment which greatly enhances the educational experience.

This paper presents the network architecture, engineering tests and their results for the Trans‐Pacific Demonstrations (TPD). The experimental network was configured using an Intelsat satellite, N‐STAR, and terrestrial networks in Japan, Canada and the United States. The TransPAC, submarine fiber‐optic link was also used as a backup for the Intelsat link. We began to establish the full‐scale experimental network in May 2000, and performed the engineering tests during about a two‐month period of the TPD. We verified the connectivity of the satellite links, ATM connections, IP and higher layers, and then measured satellite link performance, ATM transmission performance, TCP/XTP performances and so on. As the result of the engineering test, we found that networks that include one or two satellite links can be used as network infrastructure for high data rate applications.

This paper describes the Visible Human (VH) part of the Trans‐Pacific Demonstrations of the G7 Information Society‐Global Interoperability for Broadband Network (GIBN) Projects. Aiming at a world‐wide Visible Human Anatomical Co‐laboratory, an application (VHP Viewer) was developed, which was used for data transmission testing (Trans‐Pacific Demonstration of Visible Human) through broadband satellite links between the US and Japan. The demonstration includes (1) remote VH database access and (2) network multi‐parallel computing access. It is shown that wide‐area database access and high‐speed multi‐parallel computing could be effectively demonstrated via broadband satellite networks by circumventing a large time‐delay by using the Mentat SkyX Gateway system and Personal File System (PFS). Elements of the demonstration verified here could be also applied to distance education and telemedicine as well as a postgenome project.

The satellite in geostationary orbit is subjected to various forces which tend to move it from its assigned GSO orbital position. This movement is primarily in the east‐west direction and north‐south direction. The latter causes an increase in inclination from the desired orbit in the equatorial plane where inclination equals zero. Station keeping is therefore required and is implemented by on‐board thrusters. This note illustrates how compenstation is achieved and what velocity changes are required and the fuel consumption necessary.