Advancement of photonic integration technology for space applications: A x-band scan-on-receive synthetic aperture radar receiver with electro-photonic beamforming and frequency downconversion capability

Synthetic Aperture Radar is a well-known technique for remote sensing applications with great advantages like uninterrupted imaging capabilities even at night or in presence of cloud cover. However, spaceborne SAR sensors face major challenges such as cost and size, which are among the barriers against their applicability for future constellations of low-Earth observation applications. SAR sensors are not compact and require large or medium-sized satellites, which cost hundreds million dollars. To solve these challenges, the recently started SPACEBEAM project, funded by the European Commission, aims at developing a novel SAR Scan-on-Receive approach, exploiting a hybrid integrated optical beamforming network (iOBFN). The compactness and frequency flexibility of the proposed photonic solution complies with the requirements of future constellations of low-Earth orbit satellites in terms of size, weight, power consumption, and cost (SWaP-C). In the design of the SCORE SAR receiver module, we target the development of an X-band receiver having a large swath width of 50 km (5 times wider than state-of-art spaceborne SAR systems), although at the same time enabling a fine spatial resolution of 1.5 m in both along-track and across-track directions. In this paper, we present specifications and preliminary design of the SCORE-SAR receiver at equipment level, where we aim at the realization of a hermetically packaged hybrid InP/TriPleX™ photonic integrated circuit (PIC) for this application. We target the design for the PIC as well as for the RF front-end and control electronics, enabling the electro-photonic frequency down-conversion of the RF signals and the fast control of iOBFN with <300 ns switching time.