The Separation of a Two-Nanosatellite System via Differential Drag
Small nanosatellites (1 to 10 kg), with their low production costs and unique mission strategy possibilities, can be inexpensively deployed in groups to maximize scientific returns. The Space Science and Engineering Laboratory (Montana State University) has demonstrated this with their FIREBIRD satellites, a two-satellite system set to observe relativistic electron bursts in the Earth’s magnetosphere. FIREBIRD separation strategy scenarios that use differential drag to influence relative satellite velocities are studied here. Relevant orbital mechanics concepts are discussed, and equations of motion are derived and incorporated into an orbital simulation model written in MATLAB. It is found that a springless separation strategy utilizing differential drag induced by differing satellite masses creates a near-constant acceleration throughout the FIREBIRD mission duration. This method is found to be a feasible alternative to the traditional springed-separation strategy. At an altitude of 700 km, a mass difference of five grams will separate the FIREBIRD satellites to a maximum allowed relative distance of 100 km in roughly a year, plus or minus eight months. Additional physics concepts which could improve the accuracy of the model are also discussed.