Optical remote sensing from space-based and sub-orbital platforms is transforming our understanding of Earth’s atmosphere; however, important gaps remain in our knowledge of key atmospheric constituents and processes. In the upper troposphere–lower stratosphere (UTLS), significant uncertainties persist regarding the spatial and temporal variability of water vapour, aerosols, and clouds, driven in part by the limited sensitivity and resolution of current observing systems. Addressing these gaps requires next-generation observing systems that deliver improved spatial and temporal resolution, enhanced information content, and the synergistic use of multiple sensors.

These needs motivate the Canadian-led High-altitude Aerosols, Water Vapour, and Clouds (HAWC) satellite mission, a Canadian climate mission that will combine observations from three innovative instruments: the Aerosol Limb Imager (ALI), the Spatial Heterodyne Observations of Water (SHOW), and Thin Ice Clouds in the Far Infrared Emissions (TICFIRE). Together, these instruments are designed to provide unprecedented sensitivity and spatial resolution for measurements of aerosols, water vapour, and clouds in the UTLS.

In the first half of this talk, I will present an overview of the HAWC mission, its scientific objectives, and the planned data products, along with a brief update on mission status and timeline. The second half of the talk will focus on the Spatial Heterodyne Observations of Water (SHOW) instrument and current efforts to push the limits of limb-scattered measurements of water vapour, with the goal of enabling some of the most spatially dense observations of UTLS water vapour from space.