THE ACCURACY OF CONTEMPORARY GEOPOTENTIAL
MODELS AND THE ACCURACY OF PREDICTED POSITIONS OF
ARTIFICIAL EARTH SATELLITES
ABSTRACT
Edwin Wnuk and Elwira Wilczynska
Astronomical Observatory of the A.Mickiewicz University
Poznan, Poland
Paper presents some results of an analysis of the influence of the Earth's gravity field
models errors on an accuracy of predicted satellite positions. Estimations of uncertainties
in satellite positions were calculated by application of an analytical theory of artificial
satellite motion. Predicted satellite positions were calculated using recent models and then
compared. Differences in predicted positions calculated for a 24-hour time span exceed
100 meters for some orbits.
INTRODUCTION
Although succeeding new geopotential models provide increasingly better description of
the Earth's gravity, their accuracy is limited. Using contemporary models one can fit the
orbit of a geodetic satellite, like LAGEOS, to precise satellite laser ranging data with the
accuracy of centimeters. However, such a precision cannot be reached in the calculations
of the predicted positions of other Earth's orbiting objects.
New applications of artificial satellites and new space projects need predicted positions of a
satellite with a high accuracy, better than 100 meters for one-two-day predictions in some
cases (Seidelmann and Kaufman, 1994). For example, the NASA Space Station will require satellite predictions to support collision avoidance computations. The US Space Surveillance System plans to maintain a catalog of at least 25 000 objects larger than I cm in
support of the Space Station (Hoots, 1994). Since the Space Station maneuverability is
limited, collision predictions must have sufficient accuracy to avoid fa1se alarms, then the
accuracy of the predicted positions of the Space Station and all of these objects must be
very high. Many other satellites, like for example, the NOAA weather satellites need a
prediction accuracy of a few hundreds meters for a span of two-three days.
198
MODELS AND THE ACCURACY OF PREDICTED POSITIONS OF
ARTIFICIAL EARTH SATELLITES
ABSTRACT
Edwin Wnuk and Elwira Wilczynska
Astronomical Observatory of the A.Mickiewicz University
Poznan, Poland
Paper presents some results of an analysis of the influence of the Earth's gravity field
models errors on an accuracy of predicted satellite positions. Estimations of uncertainties
in satellite positions were calculated by application of an analytical theory of artificial
satellite motion. Predicted satellite positions were calculated using recent models and then
compared. Differences in predicted positions calculated for a 24-hour time span exceed
100 meters for some orbits.
INTRODUCTION
Although succeeding new geopotential models provide increasingly better description of
the Earth's gravity, their accuracy is limited. Using contemporary models one can fit the
orbit of a geodetic satellite, like LAGEOS, to precise satellite laser ranging data with the
accuracy of centimeters. However, such a precision cannot be reached in the calculations
of the predicted positions of other Earth's orbiting objects.
New applications of artificial satellites and new space projects need predicted positions of a
satellite with a high accuracy, better than 100 meters for one-two-day predictions in some
cases (Seidelmann and Kaufman, 1994). For example, the NASA Space Station will require satellite predictions to support collision avoidance computations. The US Space Surveillance System plans to maintain a catalog of at least 25 000 objects larger than I cm in
support of the Space Station (Hoots, 1994). Since the Space Station maneuverability is
limited, collision predictions must have sufficient accuracy to avoid fa1se alarms, then the
accuracy of the predicted positions of the Space Station and all of these objects must be
very high. Many other satellites, like for example, the NOAA weather satellites need a
prediction accuracy of a few hundreds meters for a span of two-three days.
198