A synthetic aperture radar (SAR) generates concurrent first radar pulses in first frequency channels. The SAR transmits, and receives returns of, the concurrent first radar pulses by first antenna feeds that form first beams in the first frequency channels and that are directed to respective first subswaths of a swath on the Earth separated by subswath gaps. The SAR generates concurrent second radar pulses in second frequency channels. The SAR transmits, and receives returns of, the concurrent second radar pulses by second antenna feeds configured to form second beams in the second frequency channels and that are directed to respective second subswaths of the swath on the Earth and that coincide with the subswath gaps. The SAR processes the returns of the first radar pulses from the first subswaths and the returns of the second radar pulses from the second subswaths to form a SAR image contiguous across the swath.