SHIMOSATO Hydrographic Observatory


SHIMOSATO Hydrographic Observatory is one of 3 observatories of Japan Coast Guard.

We have been carrying out Satellite Laser Ranging and Lunar Occultation observations in order to maintain and improve the accuracy of the nautical charts and the nautical almanacs.

The observation data by SLR are being used for the investigation about the earthquake also.

Status of data and the results of analysis are reported through the internet as DATA REPORT (ASTRONOMY AND GEODESY, SATELLITE GEODESY)

On-line local lunar occultation prediction service

Satellite Laser Ranging Observation

Japan Coast Guard has been establishing the marine geodetic network around Japan, primarily for the purpose of maintaining precise nautical charts, based on the space geodetic observations.

SHIMOSATO Hydrographic Observatory is designated as the primary reference point in this network and its geographical coordinates has been monitored through the satellite laser ranging observation since 1982.


In this technique, a laser ranging system shoots out laser pulses targeting at a satellite and receives the reflected signals. It measures the round travel time of the light, which can be transformed into the distance up to the satellite. Accuracy of this measurement reaches a few centimeters.

There are 30-40 laser ranging observatories distributed all over the world. By exchanging data through the data center, we determine the precise the position of Shimosato based on the global data analysis.

The satellite laser ranging observation also contributes to the precise orbit determination of the various satellites for the geodetic and geophysical purposes. 

The observation data of SLR and GPS being carried out in SHIMOSATO Hydrographic Observatory are being used for the detection of crustal movement of the land and the seafloor also.

(jump to ILRS: International Laser Ranging Service)

Astronomical Observation

Astronomical Observations are being carried out at a number of observatories in each country in order to determine the position of the celestial bodies.

At Shimosato, we are engaged in the lunar occultation observations and their analysis. (jump to ILOC: International Lunar Occultation Center)

Obtained lunar occultation data contribute to the calculation of the motion of the moon.


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