The European Space Agency (ESA) is exploring the technical feasibility and the scientific value of the receive-only SAOCOM-CS satellite to be launched with Argentina's L-band SAR satellite SAOCOM. The two satellites would fly in formation, with SAOCOM acting as an illuminator, enabling for the first time single-pass SAR interferometry at L-band. In order to be ready for launch with SAOCOM-1B, the companion satellite is built from components with high technology readiness. This paper presents the current status of preparation and outlines the mission timeline, system concept, instrument architecture and SAR performance, including the links to science applications.