Communications Research Laboratory
4-2-1 Nukui-kita, Koganei, Tokyo 184-8795, Japan
On the other hand discussions for the next generation global navigation system (GNSS), and how Japanese government can contribute to this system has been made on several occasions.
Depending on such discussion, the committee of space development of Japan made a scenario for next generation GNSS.
Its basic policy is:
Japan should establish basic research and development items to contribute to the next generation GNSS, such as on board atomic clock, precise time and frequency transfer between ground clock and satellite on board clock and precise and real time orbit determination technique.
CRL has started research and development on the above items during this fiscal year.
|(1)||Development of on board Hydrogen Maser type frequency standard; Atomic standard section is in charge of this item. They started development of Hydrogen Maser type frequency standard in cooperation with a Japanese private company. They are going to construct a prototype within four years. It will be have almost same frequency stability as a laboratory type and its weight will be 50 - 70 kg.|
|(2)||Highly accurate time and frequency transfer technology between ground station and satellites: Frequency and time standards section started development of an accurate time and frequency transfer technique between space and ground station. They are planning to use two way transmission mode to cancel the effects of propagation medium, such as ionosphere and troposphere, and use carrier phase of the signal to obtain precise measurement.|
|(3)||Highly precise and real time orbit determination technique. Concerning this item, CRL has just started discussions concerning the method which should be most suitable for the next generation GNSS system.|
A working group for the satellite navigation system was organized by the
members of CRL and NASDA to discuss the function of the ETS-VIII on-board
atomic clock equipment and experiments using it.