Orbital Dynamics and System Analysis of Nanosatellite in Decaying Orbit

This paper aims to highlight the attitude determination and control of a 2-U class Nanosatellite in a decaying orbit. The ever-increasing space debris in the Low Earth Orbit (LEO) poses a significant threat to operational spacecraft. This paper aims to describe an inexpensive, space and mass efficient passive deorbiting system using an electrodynamic tether. It works as an independent and autonomous system, using only electrodynamic drag to achieve deorbit. An attitude control system to ensure the working of payloads onboard the satellite and establish communication with the ground station during deorbiting has been further discussed. The attitude of the satellite is determined using onboard sensors: Sun sensors, a three-axis magnetometer, and a gyroscope. An orbit propagator (OP) model has been used to estimate the orbital parameters calibrated once per orbit utilising a GPS. A Quaternion Estimator (QuEst) and proportional-derivative (PD) controller is used for calculating the desired rotation and the corresponding torque required to orient the satellite. A complete three-axis stabilisation is achieved using the two actuators onboard the satellites: the magnetorquers and three-axis reaction wheels that apply the desired torque. The voltage developed in the tether system and accordingly the force produced have been modelled. The results indicate a period of less than one year for complete deorbiting. An extensive analysis of the control of the satellite and the force acting on the satellite-tether system during the ejection phase and a deorbiting phase has been discussed, and the simulation results have been provided.