A report of the United States Coast and Geodetic Survey for 1891-1899 records an agreement reached by members of the International Geodetic Association to establish six observatories for the purpose of measuring the variations in latitude caused by the earth's wobble on its polar axis. This program, known as the International Polar Motion Service, was initiated in 1899 with the establishment of six stations, all located near the parallel of 39° 08 ' North latitude to permit uniform computations. The observatories were:

Gaithersburg, Maryland
Carloforte, Italy
Tschardjui, Russia
Mizusawa, Japan
Ukiah, California
Cincinnati, Ohio

These six observatories worked closely together carrying out a program of star study selected by Dr.Hishashi Kimura, astronomer in charge of the Mizusawa station. Twelve groups of stars, each containing six pairs at small distances not exceeding 24 degrees and two pairs at a greater distance of 60 degrees were selected. Two groups of the stars were observed each night at each station in accordance with a schedule of dates, time, and duration prepared by Dr. Kimura. The irregular daily motion of the Earth's axis was believed to be extremely small, but the extent could be determined by precise measurements of the stars.

U.S. Department of Commerce Drawing 1967
This drawing shows the location of the six observatories on the parallel of 39 degrees 08 minutes North latitude.

Data gathered from the observatories established in 1899 is still used by scientists today, along with information obtained from satellites, to determine polar motion; the size, shape, and physical properties of the Earth; to predict climate and earthquakes; and to aid the space program through the precise navigational patterns of orbiting satellites.

To help coordinate the research of the six stations, which came to be known as the International Latitude Service (ILS), a Central Bureau was created. The directives from the Bureau were that each station must present a report once a month and, especially, must send the original book of latitude observations. The Central Bureau was placed at first in Berlin and Potsdam, Germany, for the years 1899-1922; then in Mizusawa for 1922-1934; and in Firenze and Napori, Italy, for 1935-1961. Finally it was placed in Mizusawa from 1962-1987.

While the observatories all started operating in 1899, and worked together documenting data to support latitude variations, world events affected their operations. In 1914, during World War I, both the Gaithersburg and Cincinnati stations were closed due to economic constraints and all contact was lost with Tschardjui, which is in Russian Turkestan. After the war, it was learned from the Russian observers that star movement data had continued to be collected in Russia until 1919. Then the observatory at Tschardjui was relocated to Kitab, Russia, and resumed operations in 1930. In 1932, the Gaithersburg station reopened and continued until 1982, but the Cincinnati station remained closed and was eventually dismantled.

After the war, things got back to normal, but that did not last long. World War II brought more complications. The observatory at Carloforte, Italy, closed during 1944 and 1945. Most surprisingly, however, is that although their respective countries were involved in the war, the scientists at the various observatories devotedly continued their observations. There are those who view this as quite incredible and others who say that the program had no bearing on the war efforts and should have continued as it did.

In their 1974 report, the Japanese observers commented on the fact that their observatory "reached the end of World War II without a bombing attack. . . " and that ". . .sending observation books and communicating with the Central bureau of the ILS in Italy were interrupted beginning in December 1942." They recall how their Director, T. Ikeda, who was over 50 years old at the time, operated the telescope himself at Mizusawa. The situation in Japan had produced a serious deficiency of staff and lack of daily needs, but Dr. Ikeda would not permit the interruption of the international observations.

On January 8, 1946, after the end of World War II, Navy Captain Service and First Lieutenant Cat of the General Headquarters of the Allied Powers (GHQ) visited the Mizusawa observatory and delivered a message from Commodore Colbert of the Coast and Geodetic Survey in the USA. In this message, ideas were proposed to restore communications with the Central Bureau of the ILS in Italy. So the observation books were sent once again and the isolated situations of the observatories slipped again into a feeling of solidarity.