a specialized astronomical observatory that studies the regularities governing the phenomenon of variability of geographic latitudes.
Latitude stations are equipped with instruments for the regular determination of the station’s geographic latitude on the basis of astronomical observations. The combined mathematical processing of the observations made at several latitude stations makes it possible to determine the position of the earth’s geographic pole on the earth’s surface at a series of moments in time and thus construct a curve of polar motion, called a polhode. The chief instruments used at latitude stations are a zenith telescope, a photographic zenith telescope, and a prismatic astrolabe.
Included within the International Polar Motion Service are five latitude stations with similar instruments, situated on the same geographic parallel—39°08′—and more or less evenly spaced by longitude; one of these stations is in the Soviet Union—the Ulug-bek Latitude Station of the Academy of Sciences of the Uzbek SSR, located in Kitab. At the same time, about 50 astronomical observatories in different countries are conducting systematic observations of variations in latitude for the immediate computation of the coordinates of the poles at the International Time Bureau and the introduction of necessary corrections in the world time scale.
Of particular scientific value for the study of polar motions have been the long-term observations with two high-precision zenith telescopes at the Pulkovo Observatory of the Academy of Sciences of the USSR; the lengthy series of observations with the zenith telescopes of the Greenwich Observatory in Great Britain; the series of around-the-clock observations of two bright stars in Poltava, USSR, conducted over a period of 40 years; the observations with the photographic zenith telescope conducted since 1915 in Washington, D.C., (United States); and the observations with two zenith telescopes, a photographic zenith telescope, and a prismatic astrolabe conducted at Misuzawa, Japan. Laser range-finding observations by artificial earth satellites began to be carried out in the mid–1970’s to determine the position of the poles of the earth.
L. V. RYKHLOVA