V. A. Potehin - Ph.D. (Eng.), Associate Professor, Arzamas Polytechnic Institute (branch NSTU)

This article describes the hardware and software to model the process of determining the orbits of spacecrafts based on measurements ranges between them. Three operating modes are considered. 1) defined spacecraft works with one passive spacecraft which movement is considered precisely known; 2) the defined spacecraft works with two passive spacecrafts which movement is considered precisely known; 3) two defined spacecrafts work in couple with each other and measure mutual ranges. For receiving an assessment of a vector of a condition of the spacecraft on an initial timepoint the method of the smallest squares is used. The type of mathematical models of true and settlement movements is defined by the user. The model of a geopotential varies from the elementary keplerovy model to the accounting of all zone, tesseral and sectorial harmonicas to 14 members. The range of indignations can be expanded, making changes to procedure of calculation of the right parts of the differential equations of movement. In this software product for numerical integration of the equations of movement Richardson's extrapolation method with an automatic choice of a step of integration is used. In need of a vector of estimated parameters it is possible to include any parameters of mathematical model of movement. For example, coefficients of decomposition of a geopotential which need to be specified. Certainly, such inclusion will demand a certain correction of some procedures of this software product. In particular, in this case it is necessary to change procedure of creation of a matrix private derivative of the measured parameter on estimated components.