Silicon nanophotonics is contributing to the development of devices with small dimensions and low energy consumption. In optical systems for space applications, whether in large or small satellites, such as CubeSat, the demand for photonic devices has been a necessity, mainly in the communication subsystem, due to limitations in the conventional optical beam pointing subsystems. Silicon nanophotonics can be a solution in this case as it allows for the construction of an optical beam pointing system without moving parts, such as optical phased array antennas, in which the component responsible for the pointing functionality is the optical phase modulator. With this objective, we propose an efficient non-resonant all-optical modulator based on an Archimedean spiral waveguide topology by means of the indirect thermo-optical effect. Computational results are presented and discussed.