Errors in determination of an object position in standard regime of satellite navigation systems functioning can amount to several meters. One of causes of such a precision level is inexactitude of ephemeris registered by receiver during satellite measurements. In gravimetry and for some other special tasks it is allowed to work up measurements not immediately but after some time, that gives a possibility to determine an object position more precise at the expense of more accurate determination of satellite coordinates and velocity. International Global Navigation Satellite Systems Service (IGS) let users of satellite navigation systems free access to the information of rather precise coordinates of every satellite in Greenwich coordinate system with two week delay. It is declared that precision level of these position data doesn t exceed 15-20mm for GPS satellites, and 50-60mm for GLONASS satellites. Data are renovated every fifteen minutes. An algorithm using precise position IGS information and estimating errors of primary determination of satellite coordinates and velocity with following their compensation was elaborated to define trajectory parameters of every satellite more precisely. As a result of applying this algorithm the trajectory of every satellite was defined as precise as IGS data. This algorithm can be used to model approximate observables for Universitetskiy-Tatyana satellite more precisely. This procedure has two steps. First, we model its motion at the certain period of time by taking the parameters of its orbit. Then, we determine approximate observables using precise trajectory of every navigation satellite.