Today’s space-borne SAR systems are polar orbiting, which yields global coverage, but with relatively long repeat cycles of 24 and 35 days for Radarsat and Envisat, respectively. By using variable incidence angles, Radarsat and Envisat are capable of acquire images from a given location with shorter intervals than the orbit repeat cycles. The frequency of how often a satellite SAR can cover a given area is dependent on the geographic location (latitude).
Our experience is that it is generally impossible to get daily coverage with just one satellite, even with variable incidence angles.