Passive Optical Links Supporting Spaceborne Low Radio Frequency Interferometric Telescope

This paper presents a novel wireless linking architecture for the spaceborne array-based low radio frequency telescope probing the Dark Age 21-cm cosmology. This gigantic radio telescope may consist of 10s to 100s of interferometric array elements, potentially using a swarm of CubeSats with individual antennae, sensors, avionics, etc. There is a significant complexity of the inter-element wireless linking architecture for both data exchange and relative positioning, navigation, and timing (PNT).The passive optical wireless linking architecture utilizes modulating retroreflectors (MRR) with ultra-low power stepped-quantum-well modulators. The MRR-based optical transceiver does not require the CubeSat to have an active laser source and the associated precision beam-pointing apparatus and may significantly reduce the spacecraft and the overall mission architectural complexity.We analyzed the passive optical communication link budget as well as the achievable relative PNT precision in a mission context of 100 distributed array elements (CubeSats) and four relatively larger spacecraft, which can carry the interrogating laser sources for the passive links, premium communication capability with Earth, and absolute PNT instruments. We will show the optimized design of the stepped-quantum-well modulator and the associated optical system design specifically is compatible with CubeSats’ size, weight, and power (SWaP) constraints.