Japan

Japan has a two-pronged approach to satellite navigation. First, to make use of the globally available US GPS System by incorporating additional features to make it more accurate and applicable for their area of interest and secondly, to develop a regional network of own satellites.

The topography and terrain of Japan does not permit the GPS signals to penetrate every portion of the country, resulting in the underperforming of the GPS system. In this nation of mountains and skyscrapers, at times the strength of signals gets depleted, and navigation systems particularly those used on the ground in various types of vehicles are found ineffective. To augment the strength of GPS, Japan has developed the MSAS (MTSAT[206] Satellite-based Augmentation System). It is essentially an overlay system for increasing the accuracy of the GPS navigation by transmitting differential information.[207] This system was conceived during the 1990s, and the first satellite MTSAT-1 was launched in 1999; however, there was a launch failure of H2 launch vehicle. The MTSAT system is designed to consist of one or two satellites, depending on the time frame and two Ground Earth Stations (GES) per MTSAT.

Finally, the first satellite in the MSAS space segment, MTSAT-1R, went into orbit in 2005. Japan launched its second Multifunctional Transport Satellite (MTSAT-2) on February 18, 2006, thus opening a new phase of precision air navigation and air traffic control (ATC) over the western Pacific Ocean. This five-ton satellite is the

heaviest ever launched by Japan and is operating in a circular geostationary orbit. The on-board transponders of this satellite offer another link for Japan’s MSAS, relaying differential GPS corrections and integrity messages to suitably equipped users. One interesting feature of this satellite is that being a multifunction satellite, first the meteorological payload of MTSAR-1R was operational for five years, and later during July 2010 meteorological payload of MTSAT-2 became prime which was earlier placed into standby mode (summer of 2006) until the end of 5 years. The system is supposed to seize off in 2015/2016.

The major beneficiaries of the MSAS are the aircraft operating on routes across the Pacific. The improved navigation accuracy and associated communication links allow the planes to operate close together along the most travelled routes. In addition to the GPS navigation data, MSAS provides data links to and from ATC control centres and facilitates the automatic transmission of aircraft locations to controllers when they are out of the range of ground-based ATC radars. In addition to the L-band GPS broadcasts, MTSAT provides voice and data communications over Ku- and Ka-band frequencies. This satellite also provides weather-related inputs.[208]

In 2000, Japanese Regional Navigation Satellite System (JRANS) concept was developed by the Japanese industry and was discussed and debated with the government representatives as well as the US government and industry personnel. Its purpose was to satisfy current and future operational requirements and assure full compatibility and interoperability with GPS.

After much deliberation during 2003, Japan has started a new project of Quasi­Zenith Satellite System (QZSS). This system consists of three satellites meant to provide a regional satellite positioning service as well as communication and broadcasting services. The configuration is such that each satellite is in three different orbit planes, which are obtained by inclining the geostationary orbit (GEO) by about 45°. At least one satellite is expected to stay around the zenith for about eight hours and would be visible with a higher elevation angle in mid-latitude area (e. g. at least 80° in Tokyo) than in case of using a satellite in GEO. This characteristic would be beneficial for large cities with several tall buildings which block the signal from satellites in GEO. This would vastly improve the satellite positioning and mobile communication services.[209]

The project is devised as a public-private partnership. The proposal is to develop a programme in a two-phase build-up of quasi-zenith (QZO), then another quasi­zenith and geostationary orbiting satellites (QZO and GEO). Phase one will have three satellites in quasi-zenith orbit, and Phase two will have four satellites in QZO andGEO [2].

Currently, Phase one of this project is underway. In QZSS, satellites are meant to orbit in a figure of eight patterns over Japan and the East Asian region. They would

be at a high elevation angle over Japan. This would make extra positioning signals available in urban Japan. The first of the QZSS satellites (known as Michibiki) was successfully launched in September 2010. The full operational status is expected by 2013.[210]

Michibiki (a name that means ‘guidance’ in Japanese) operates from an altitude of about 40,000 km. Japan has developed this satellite as a multipurpose satellite for aircraft, tsunami detection and ground traffic management. But the Michibiki alone cannot be the solution. As mentioned earlier, each satellite would be above Japan for about 8 h each day; hence, all three satellites are required for 24-h coverage.

Japan has a cooperative agreement with the USA since 1998 for use of GPS for civilian purposes. This was reviewed on January 13, 2011. During this meeting, the extent of cooperation was extended to include Japan’s Multifunctional Transport Satellite (MTSAT), Satellite-based Augmentation System (MSAS) and Quasi­Zenith Satellite Systems (QZSS).[211] Japan’s policy appears to be to develop its own regional system and also have maximum benefits from the GPS.