MIZUSAWA, JAPAN
The NAO Mizusawa
International Latitude Observatory was one of six observatories
in a world-wide network of observatories established in1899
by the International Geodetic Association. These were widely
distributed in longitude but all situated on the same parallel
of latitude (39 ° 08'). The purpose was to monitor the
earth's variable rotation, or in simpler terms, to solve the
problem of why the earth "wobbles" on its axis.
The six observatories worked under the direction
of Dr. Hisashi Kimura, astronomer in charge of the Mizusawa
station.
In 1970, a working group was
formed to clarify the results of the observations done by
the six observatories starting in 1899. The difficult and
time consuming task of recalculating the observations, by
employing the original observation books, was assigned to
the staff of the Mizusawa Observatory under the direction
of Dr. Yumi.
The observation books, or their
photocopies, were collected at Mizusawa and all data transformed
into a machine-readable form. Then corrections were made and
a "homogeneous system" developed for interpretation.
The product of this effort was a highly technical, two-hundred
page report printed in 1980 which, although difficult for
the average person to understand, confirms, among other things,
the exact dates of operation of the six observatories.
About a decade later, in 1988,
in a letter responding to an inquiry from Mayor Edward Bohrer
of Gaithersburg, which also has a similar historic observatory,
Professor K. Yokoyama explained that advancement in technology
had lead to the closing of the historic observatories.
In accordance with the development
of new space techniques for monitoring the Earth's rotation
since late 1970s, relative importance of classical techniques,
such as ILS (International Latitude Service) network, has
rapidly decreased. This has resulted (in) replacement of observation
techniques, as well as reorganization of international networks.
For example, the National Geodectic Survey, which has been
responsible for operating two US stations, closed them in
1982 and initiated new observation by means of radio interferometric
technique.
Mr. K. Yokoyama went on to
say that the 1899 Mizusawa Observatory was eventually revived
as the Earth
Rotation Division of the new National Astronomical Observatory
since July of 1988.
Current
staff for the Earth Rotation Research
Location
of today's Mizusawa Astrogeodynamics Observatory
Both Mizusawa and Gaithersburg,
who consider themselves to be "sister
cities," have acknowledged the 100th anniversary
of the observatories in their respective cities.
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