Direct Reception Satellite Broadcasting Concept
If radio waves can be transmitted from an artificial satellite in space, simultaneous communications, or broadcasting, over a wide area will be possible. If the transmission is made by a geostationary satellite revolving around the earth with the same period as the earth’s rotational period, three satellites can cover the entire world with the exception of the North and South Pole areas. This idea was first proposed by the science fiction novelist Arthur C. Clarke in 1945.
Twenty years later, in 1965, NHK President Yoshinori Maeda announced a plan to provide satellite broadcasting that could be directly received at individual homes. It was to make nationwide broadcasting in Japan feasible.

Research Begins on Broadcasting Satellite
In 1966, STRL initiated research on various aspects of such a satellite system, including the satellite bus system, control system, transponder, and home receiver. A small, elliptical low earth orbit satellite was designed and manufactured as an A-type satellite (approx. 10 kg) for one audio channel, and a B-type satellite (approx. 45 kg) for one TV channel. Various tests were performed using the newly established space environment laboratory.
While these satellites were quite small in comparison to the current broadcasting satellites, which weigh over 500 kg, they provided valuable experience. The satellites were completed in 1968.

Research Advances for Implementation
Japan started a full-scale national development plan for a practical satellite, establishing the National Space Development Agency of Japan (NASDA) in 1969. At a meeting of the World Administrative Radio Conference held in 1971, it was determined that the 12-GHz band should be used for satellite broadcasting.
The Space Activities Commission approved a development plan for an experimental broadcasting satellite (BS) in 1973, reflecting NHK’s research results, such as those dealing with transponders and antennas for satellites. Researchers from NHK were stationed in the U.S. to provide the General Electric Company (GE) with engineering and manufacturing support for the transponder. Others were sent to NASDA on loan to participate in promoting the project.
The BS was equipped with three 100-W TWTs, which were high-powered transponders for a satellite at that time, to provide broadcasting on two channels. It adopted a three axis stabilizing system for its attitude control, instead of the conventional spinning stabilizing system.

Satellite Broadcasting Channel Plan
Radio waves transmitted from outer space can easily reach many different countries. For this reason, limited radio frequencies and geostationary orbital positions need to be allotted to each country. Given a rising trend in satellite broadcasting throughout the world, the World Administrative Radio Conference (WARC-BS) in 1977 assigned a broadcasting satellite orbit location and frequencies to each country.
NHK, by making good use of a computer program developed at STRL, contributed to the channel assignment plan at this meeting. This resulted in Japan being assigned eight channels, which was a larger channel assignment than those for European countries.

1. Geostationary satellite concept
2. A- type satellite, B-type satellite of STRL