Abstract
The High-altitude Aerosols, Water vapour and Clouds (HAWC) mission is an observing system, with a planned launch around 2031, that is being developed by the Canadian Space Agency to provide co-located global measurements of aerosols, water vapour, and thin ice clouds in the upper troposphere and lower stratosphere with vertical coverage that extends into the troposphere in the polar regions. The mission is the Canadian contribution to NASA’s Atmospheric Observing System (AOS, aos.gsfc.nasa.gov); a satellite constellation that will include multiple instruments to monitor aerosols, clouds, and precipitation as part of the Earth System Observatory (ESO,https://science.nasa.gov/earth-science/missions/earth-system-observatory). The HAWC mission includes three innovative Canadian instruments: the Aerosol Limb Imager (ALI), the Thin Ice Clouds and Far InfraRed Emissions (TICFIRE) instrument, and the Spatial Heterodyne Observations of Water (SHOW) instrument. ALI and SHOW will provide limb profiles of aerosol and water vapour with high spatial resolution (vertical and along-track) and high sensitivity to fine aerosols and dry conditions. TICFIRE will provide nadir measurements of infrared radiation, thin ice cloud content, and cloud microphysical properties. These coordinated measurements will help build a more comprehensive picture of high-altitude aerosols, clouds, and water vapour in the atmosphere. In this paper, we present the HAWC concept and discuss the primary science objectives and requirements of the mission. The instrument payloads and data products are introduced and synergies between HAWC and other AOS instruments are identified.
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