Abstract: A thermal management system for a spacecraft includes a plurality of T-shaped pallets each having a radiator panel and mounting panel. The radiator panels are connected end to end to enclose an interior space including the mounting panels. The mounting panels have electronic equipment mounted thereon. L-shaped external heat pipes contact both the mounting panel and radiator panel of each pallet to provide heat transfer from the electronic equipment to the radiator panel when the radiator panel is facing away from the sun. In order to cool the electronic equipment mounted on a pallet facing the sun, a closed-loop heat pipe is disposed in the interior space and each pallet inclues L-shaped internal heat pipes contacting the closed-loop heat pipe and the mounting panel. Heat generated in the electronic equipment of the pallet facing the sun is transferred to the internal heat pipes via the mounting panel and then to the closed-loop heat pipe.