Space-Time Standards Laboratory

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NICT >Applied Electromagnetic Research Institute >Space-Time Standards Laboratory

Four Groups of Space-Time Standards Laboratory have conducted research and development.

Japan Standard Time Group

Japan Standard Time Group is responsible for generating and keeping JST based on UTC(NICT), comparing UTC(NICT) using international time-transfer link, disseminating the standard time and frequency called JJY, and providing useful information and data on time related business applications and solutions.

Atomic Frequency Standards Group

We are conducting research to develop atomic clocks with ultra-high accuracy, aiming for the establishment of accurate standard of time and frequency.

Space-Time Measurement Group

Space-time Measurement Group conducts research and development on space and time measurement technologies using radio and optical waves.

Satellite Time Management Group

We are developing the time management system for the quasi zenith satellite system (QZSS), and also carrying out precise time and frequency comparison experiments between a clock on a satellite and the clocks on the ground using ETS-VIII (engineering test satellite 8).

　Introduction

Both time and position are important and fundamental indices of almost everything in social life and scientific research. Researchers in Space-Time Standards Laboratory are conducting research and developments to establish standards and reference of space and time, and to provide easy access to these foundations from wide range of communities.

　Japan Standard Time Group

Japan Standard Time Group is responsible for the important tasks for determining and maintaining Japan Standard Time as well as Standard Frequency, and providing them to all over Japan- tasks directly linked with the daily lives of the Japanese people.
1. “generating” highly precise JST using atomic clocks
2. “comparing” standard clock times of JSTP with those of　other standard organizations around the world
3. “providing” them to the Japanese people with various methods
JSTP introduces a wide range of services based on the key roles mentioned above. In addition, JSTP has conducted research and development on Time Information Service and applied technology by using Networks such as Time-Dissemination via Internet, Electronic Time Authentication and so on.

　Atomic Frequency Standards Group

The second is defined by the frequency of the microwave, absorbed or emitted by cesium atoms. It is actually very difficult to obtain the microwave, whose frequency strictly corresponds to the defined one.
Members in the Atomic Frequency Standards Group are conducting research to develop atomic clocks with ultra-high accuracy, aiming for the establishment of the standard of time and frequency with ultra-low uncertainty.

Space-Time Measurement Group

Space-time Measurement Group conducts research and development on improving the precision of the time and frequency transfer techniques by two-way measurement with satellite and by GPS signal reception in order to contribute to the generation of the universal coordinate time (UTC), and the frequency transfer using optical fiber to compare highly stable atomic frequency standards.
In addition, our project furthers the space and time applications of the portable ultra-small VLBI (Very Long Baseline Interferometer) in collaboration with Geographical Survey Institute. This ultra-small VLBI system is expected to be applied to the frequency transfer among remote places.

Satellite Time Management Group

　We developed an on-board precise time comparison equipment (TCE) and are carrying out time and frequency comparison experiment and a ranging experiment between an atomic clock on a satellite and the clocks on the ground using the TCE on ETS-VIII (engineering test satellite 8). The precision for the comparison reaches 3 pico (3 trillionths) seconds, which makes on-board monitoring of the atomic clock possible.We are also developing the time management system for the quasi zenith satellite system (QZSS), whose first satellite is scheduled to be launched in 2010, under a contract to the ministry of internal affairs and communications (MIC). The time management such as a monitoring the on-board clock will serve for the interoperability with GPS.