Design of Orbit Debris Environment and Collision Alert System

Since the number of targets near the earth orbit has already been beyond 9000, it is necessary and much important to analyze targets near the mission orbit to bring the mission to access both before the launch and during the orbital mission. NORAD maintains general element perturbation element sets (Two-Line Element Sets, TLEs) on all resident space objects. In turn, these element sets are provided to users. These element sets are periodically refined so as to maintain a reasonable prediction capability on all space objects. At the same time, NORAD developed a set of models named SGP/SDP series as models for propagation of NORAD element sets. Five mathematical models for prediction of satellite position and velocity are available. And the NORAD element sets are currently generated with either SGP4 or SDP4 depending on whether the satellite is near-Earth or deep-space. These two models, SGP4 for "near-earth" objects and SDP4 for "deep space" objects, are widely used in satellite tracking software and can produce very accurate results when used with current NORAD two-line element datum. A brief review is taken at these element sets and propagation models first. Then through the precision analysis, it is believed that using SGP4/SDP4 models for taking quick collision alert among space targets is suitable. Based on this conclusion, an orbit debris environment and collision alert system was designed. In this system, targets and the corresponding TLEs are saved in a database based on MS SQL Server, and the data visual is realized by OpenGL. The orbit propagation models being used is SGP4/SDP4 since this model is the generator of current TLEs and will be supported in the future.