Session
Technical Session XIII: Poster Session
Abstract
In certain low Earth orbit (LEO) satellite missions it is required that two or more satellites must operate in a certain spacial configuration relative to each other. This paper introduces a simple concept of utilising aerodynamic drag to achieve this type of constellation control. A necessary structural requirement for the satellites is that a change in projected area on a plane perpendicular to the velocity vector of the satellite can be brought about by means of an orientation adjustment. The aerodynamic force acting on the satellite can thus be controlled through a simple eigenaxis slew of a three-axis stabilized satellite. The slew can be done through conventional means, including thrusters, momentum exchange methods or magnetorquers. The presence of a GPS receiver on the satellite is necessary for accurate position information. It is shown that certain critical parameters influence the bounds of control time and accuracy. These parameters include the physical properties of the satellites, the orbital configuration and the state of the atmosphere. A control system to illustrate the concept is proposed and tested through detailed computer simulations. The simulations include the influence of other orbit perturbation forces acting on the satellite, like the effects of the Earth's oblateness, solar radiation pressure and lunisolar attractions. Cowell's method is used to integrate the equations of motion numerically. Typical results for two satellites (mass: 10 kg; maximum cross-sectional area: 0.3947 m2 ; minimum cross-sectional area: 0.0875 m2 ) in a 450 km circular orbit are as follows: the two satellites can be moved 500 km apart within 98 orbits (~153 hours). The distance error is less than 1%. The additional altitude loss due to the control effort is 1.53 km. The control time drops sharply for lower altitudes and higher area-to- mass ratios of the satellites. For a 300 km altitude orbit and the same satellites, the control time is 30 orbits (~45 hours) with a distance error less than 1%. The additional altitude loss in this case is 5.20 km. The concept proposed in the paper introduces a very useful method of constellation control. The key feature is utilizing aerodynamic drag, a natural phenomenon which is normally considered as an unwanted disturbance, especially for low Earth orbit missions. The structural and software requirements placed on the satellites are not stringent or restrictive and should easily be reconcilable with requirements arising from the primary mission objectives.
Using Atmospheric Drag for Constellation Control of Low Earth Orbit Micro-satellites
In certain low Earth orbit (LEO) satellite missions it is required that two or more satellites must operate in a certain spacial configuration relative to each other. This paper introduces a simple concept of utilising aerodynamic drag to achieve this type of constellation control. A necessary structural requirement for the satellites is that a change in projected area on a plane perpendicular to the velocity vector of the satellite can be brought about by means of an orientation adjustment. The aerodynamic force acting on the satellite can thus be controlled through a simple eigenaxis slew of a three-axis stabilized satellite. The slew can be done through conventional means, including thrusters, momentum exchange methods or magnetorquers. The presence of a GPS receiver on the satellite is necessary for accurate position information. It is shown that certain critical parameters influence the bounds of control time and accuracy. These parameters include the physical properties of the satellites, the orbital configuration and the state of the atmosphere. A control system to illustrate the concept is proposed and tested through detailed computer simulations. The simulations include the influence of other orbit perturbation forces acting on the satellite, like the effects of the Earth's oblateness, solar radiation pressure and lunisolar attractions. Cowell's method is used to integrate the equations of motion numerically. Typical results for two satellites (mass: 10 kg; maximum cross-sectional area: 0.3947 m2 ; minimum cross-sectional area: 0.0875 m2 ) in a 450 km circular orbit are as follows: the two satellites can be moved 500 km apart within 98 orbits (~153 hours). The distance error is less than 1%. The additional altitude loss due to the control effort is 1.53 km. The control time drops sharply for lower altitudes and higher area-to- mass ratios of the satellites. For a 300 km altitude orbit and the same satellites, the control time is 30 orbits (~45 hours) with a distance error less than 1%. The additional altitude loss in this case is 5.20 km. The concept proposed in the paper introduces a very useful method of constellation control. The key feature is utilizing aerodynamic drag, a natural phenomenon which is normally considered as an unwanted disturbance, especially for low Earth orbit missions. The structural and software requirements placed on the satellites are not stringent or restrictive and should easily be reconcilable with requirements arising from the primary mission objectives.
