In this thesis, the development of a deployment mechanism for a primary mirror of a space telescope is discussed. A mistake has been found in the earlier work on the design of this subsystem, due to which the design is set back to a concept selection phase. A trade-off has been made between several concepts. A simplified thermal model that assessed those concepts shows that none of them will be able to fulfill the thermal requirements. As a result another more complex concept that integrates the deployment mechanisms of the primary and secondary mirror has been developed. Attention has been paid to athermalization, actuator design and the design of the ribbon connecting the primary and secondary mirror. The thesis shows that it is feasible to meet all requirements, except for the one that defines the mass budget, by improving upon the current preliminary design during future work.