Modifications required to a SAR constellation mission are addressed in order to achieve bistatic observations under a range of bistatic angles, in a cost effective and flexible fashion. In particular, the paper investigates achievable performance deriving from an evolution of COSMO/SkyMed towards bistatic applications. A mathematical model is presented, which allows evaluation of bistatic angles as a function of latitude and longitude, on the basis of orbits’ propagation and spherical trigonometry. Results show that while nodal separation increases, a target is observed under a variable bistatic angle, which is not an increasing monotonic function of time due to the varying position of orbits’ intersections and thanks to electronic beam ste...