Degree Name

Master of Engineering (Hons.)


Department of Mechanical Engineering


The trajectory analysis of a celestial object orbiting another body is the basis for all other, more complex theories of spacecraft motion. It is also highly important for the design and construction of spacecraft. New computer software SATELIGHT is developed for computing the satellite coordinates with respect to the Earth centre or to the point on its surface, in orbit plane or in right ascension system. A dynamic model is presented by second order differential equations solved numerically. The numerical method used is Runge Kutta IV order. Initial conditions are based on the orbit characteristics - shape and orientation, and are result of mission objectives and constraints analysis. The model is developed gradually. The starting stage is solving the so-called Kepler's two body problem which includes only gravitational force without any perturbing forces. This model is ftirther modified for anomalies of the Earth gravitational field, atmospheric drag and three body problem - influence of Moon on the trajectory of the Earth satellite. The model for the Three-Body perturbation gives solution for any situation in the space and computes change in the orbit inclination angle. The coordinates are obtained in numerical form with adjustable precision, depending on the computer capability. Results could be transferred to the Excel and by using a particular program could be imported into ACAD and plotted as a drawing file. This gives great visual presentation in two dimensions, with opportunity to effectively compare, measure and fiirther manipulate imported data. This work is primarily concerned with unmanned Earth orbiting spacecraft but the basic principles are sufficiently broad to be applicable to any situation. The advantage of this software is its flexibility to be modified for any specific situation required by initial or environmental conditions.