Tokyo - September 7, 1996 -- An alternate Japanese GPS system have been thrown into doubt following the refusal of the Science and Technology Agency to allocate funding. Initially developed under a research project sponsored by the National Space Development Agency (NASDA), the plan was to deploy a four-satellite test system by 2002 to support local GPS systems within Japan and the Asian region.

A report by NASDA was submitted to the Science and Technology Agency, which oversees NASDA this July. The report clearly stated the need for a new GPS system to replace the current GPS later this decade.

"The operation of the current GPS is quite complicated and the accuracy is limited, especially for daily life usage. The system relies on a lot of ground bases and satellites and suffers from high operational costs," says Kiyoshi Higuchi, director of NASDA's policy department, who believes the current GPS accuracy will not be sufficient for the anticipated boom in future applications.

NASDA's answer is to develop a new regional GPS technology system and begin launching it in 2002, with the option of building a complete system later. Higuchi envisions a trial family of one geostationary and three elliptical satellites to begin with. Total cost of the system is estimated at 70 billion yen. The projected coverage area would stretch from the northern coast of Indonesia to the tip of the Kurile islands north of Japan, and from western China to Guam. The proposed accuracy of the system would be 10 meters compared to the current system's 30 meter best.

"I think building the elements of the system aren't as difficult as developing a system as a whole. Triangulation relies on time accuracy built on durable, lightweight atomic clocks. Along with signal generator and software development," he said.

"We still have to make decisions ourselves on which system is best in terms of distribution of the satellite and what we can save in terms of cost. We need more study because of the developing requirements of the end-users too," he added.

"There are four main technical obstacles" to the development of the Japanese version, according to Jun Gomi, a NASDA engineer and part of a ten-man team responsible for producing the report. They are "Orbit placement accuracy, on-board time accuracy, atmospheric distortion compensation and calculating the appropriate orbit." Of these "the first two are very important," he says. "We need to be able to get the satellite within one meter of it�s intended position if we are to meet later positional accuracy requirements," he said.

Research into how to increase placement accuracy is due to be conducted aboard the recently launched Advanced Earth Earth Observation Satellite's Retroreflector In Space (RIS) laser system, he said.

The on-board atomic clock is the biggest headache. "Currently only the US and the Swiss have the technology to build such clocks," he said. Overcoming atmospheric beam distortion is the least of the worries. The US system overcome this using the L-band (1.5-1.6 GHz) frequency.

Whatever happens, the politicians aren't ready yet. "The Space Activities Commission has allowed NASDA and STA to begin a first phase preliminary study, but they have decided that it is two early to decide whether we should go to phase two for preliminary design," said Higuchi.

SAC has allowed us only to study the issue, not to build anything. Beyond this, it's a matter for the Japanese Government to decide," he added.

It hasn't been a case of NASDA being over-quick or the policy makers tardy, according to Mitsugi Chiba, Director of the space policy division of STA. "The Space Activities Commission conclude that it was just too early to decide upon the basic principles or direction for a Japanese-led GPS system," Chiba said.

The fundamental question is what kind of system the world needs, and whether Japan should develop its own independent technology," he added.

Chiba thinks that NASDA has been on time with its proposals, and that the pressure to move on the issue is mounting. "STA is due to begin discussing the issue soon, I personally want us to reach a conclusion next spring. NASDA will resubmit their proposal next year, and we should be ready to answer them," he said.

"Tthe US is our friend, but we need to establish our own system, or at least develop the technology to do so," he said. The alternative, he suggested, would be to commit the world to an inferior standard.

"NASDA is an implementing agency, we only prepare the technology. We feel that if there is a new global system we should contribute. We don't know what the Government or the International community are going to decide. But no matter what happens, we need the technological base to establish our own system," he said.

09.07.96