Prof. Dimitra Rigopoulou

Abstract:

The Line Emission Terahertz Observatory (LETO) is a candidate European Space Agency (ESA) M8 mission designed to investigate the interstellar medium, star formation, and the evolution of galaxies through velocity-resolved spectroscopy of key far-infrared emission lines. To meet the demanding sensitivity, spectral-resolution, and mapping-speed requirements of the mission, LETO will employ multi-pixel heterodyne receiver arrays operating across four frequency bands between 0.45 and 5.5 THz.

This paper presents proposed concepts for the LETO Band 1 array receiver, which targets the frequency range below 1 THz using superconductor-insulator-superconductor (SIS) mixer technology. A wideband SIS mixer design covering the baseline 450–650 GHz frequency range is described. The design builds upon proven receiver technologies developed for astronomical instruments, thereby reducing technical risk while maintaining near quantum-limited sensitivity.

Two complementary array architectures are investigated. The first employs a conventional single-polarisation mixer configuration that can be reconfigured to support either single- or dual-polarisation observations. The second is based on a fourprobe dual-polarisation mixer concept that eliminates mechanically reconfigurable optical components while providing flexible observing modes. Several operational configurations are presented, demonstrating how the proposed architecture can balance sensitivity, mapping speed, and spacecraft resource constraints. These concepts form the basis for future development of the LETO Band 1 receiver should the mission progress to subsequent study phases.