Sliding Mode Attitude Control for Small Satellites with Manipulator

Small satellites are making their way into different space missions: from Earth Observation to Space Exploration, the number of less-than-500kg satellites in space is going to increase. Thanks to their low cost, accessibility and relatively easy to make, small satellites are the choice for a several Universities, research centers and some government agencies. With the advancement in technology, even the space robotics can finally employ small satellites as manipulator carriers. In the past, space robotics was limited to conventional spacecraft like Canadarm on the Space Shuttle or other robotic arms mounted on the Mir or ISS only. Such space robots could perform several tasks like inspection, maintenance, assistance, repair and in-orbit assembly. In the case of assistance, inspection and repair the small satellite could be used to fix other satellites, increasing their lifetime, avoiding the need to launch a replacement and reducing even more the mission’s cost. Since one small satellite-based manipulator could assist and fix more than one satellite and, given their relatively modest dimensions and mass, several of them can be place in orbit with one launch vehicle the overall cost saving is very relevant. These new types of missions and small satellites could open a new space business focused in repairs also. The challenges that arise with small satellites equipped with manipulator are the reactions of the two subsystems that influence each others. Such reactions, in these cases, may be relevant and no more negligible as the case with satellites or spacecraft with bigger dimensions. This forces, torques and accelerations can affect the attitude precision.