Submillimeter-wave and Terahertz Receivers for Lunar Volatiles Experiment

Water is fundamental to life on Earth and is a key molecular marker for a habitable environment. Yet, after decades of solar system exploration, the origins, abundance, and distribution of water in planetary bodies are still debated. The Moon system is close to us, and water on the Moon is of great interest to the exploration community as a resource to support future robotic missions and astronauts on long-term missions. For these reasons, developing advanced sensors to measure the distribution of water is of interest, with deployability facilitated by high sensitive, compactness, and low power requirements. This article presents advancements in submillimeter and terahertz receivers to support the Submillimeter Solar Observation of Lunar Volatiles Experiment (SSOLVE). SSOLVE is under development as a candidate for NASA's exploration of the Moon in forthcoming lunar lander missions, to measure water vapor above the lunar surface. SSOLVE measures the column abundance of water vapor (H₂O) at 556.93 GHz and its primary photolysis product, Hydroxyl (OH) at 2.509 THz in absorption against thermal emission by the Sun to quantify abundance in the lunar exosphere. This manuscript primarily focuses on the SSOLVE's front-end optics and receivers while introducing other parts of the instrument.