Kharkov State Research Institute of Metrology, Mironositskaya st. 42, 310078 Kharkov, Ukraine
Nowadays the techniques and instrumentation of the classic as well as
the modern astrometry are widely used in the space researches, in the
study of the Earth as a planet, in the decision of the problems of
ecology and earthquakes forecast etc. [1]. The errors of the currently
available methods of determination of the astronomical refraction are
0,01 arc seconds in theory and 0,1 arc seconds in experiment. The
errors of the range measurements (for example in SLR observations) in
most cases may run between 2 and 3 cm. These errors in sight will be
reduced to 0,0002 - 0,0005 arc seconds for angle measurements and to
0,1 - 0,3 cm for distance one. The Earth's atmosphere effect on the
results of observations is one of the major cause of decreasing in
accuracy of astrometric methods. Because of this, the problem of
development of new methods of determination of atmospheric corrections
in astronomy, SLR, VLBI, GPS observations remains the topical one.
The present paper suggests to resolve this problem by using the
integral approximation of ray optics [2]. The principle of this
approximation is following: instead of the differential ray equations
of the geometrical optics its integral analogues - the algebraic
relationships among the quantities averaged along the geometrical
optics rays and describing refractive ability of atmosphere as a whole
- are considered. For quantitative description of effective refractive
area sizes of atmosphere the new parameter - the length of atmospheric
portion of ray trajectory - is entered. The formulae for computation
of atmospheric corrections therewith are represented as a series in
terms of power of this length.
The studies conducted shown that the new approach made possible the
accuracy rise in determination of atmospheric refractivity corrections
by meteorological data measuring at point of observation. In
particular, the accuracy of the new algorithms of determination of
astronomical refraction and atmospheric refractivity corrections in
SLR were tested by numerical experiment with the use of 125 radiosonde
profiles obtained at the Kharkov's meteorological station throughout
1979. It was shown that under experiment conditions for zenith angles
between 0 to 80 degree the systematic error of proposed method did not
exceed than 0,1 - 0,9 cm whereas the Marini-Murrey's method under
these conditions gave the systematic error of 0,39 - 2,67 cm. Therewith
the accuracy of new methods of computation of astronomical refraction
by ground meteoparameters may be in 4 - 100 times greater than
accuracy of known Pulkovo refraction tables [3].
The prospects of the further development of the technique of integral
approximation of ray optics and its astrometric applications are
discussed.
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