The Aerosol Limb Imager: acousto-optic imaging of limb-scattered sunlight for stratospheric aerosol profiling

摘要

The Aerosol Limb Imager (ALI) is an optical remote sensinginstrument designed to image scattered sunlight from the atmosphericlimb. These measurements are used to retrieve spatially resolvedinformation of the stratospheric aerosol distribution, includingspectral extinction coefficient and particle size. Here we presentthe design, development and test results of an ALI prototypeinstrument. The long-term goal of this work is the eventualrealization of ALI on a satellite platform in low earth orbit, whereit can provide high spatial resolution observations, both in thevertical and cross-track. The instrument design uses a large-aperture acousto-optic tunable filter (AOTF) to image the sunlitstratospheric limb in a selectable narrow wavelength band rangingfrom the visible to the near infrared. The ALI prototype was testedon a stratospheric balloon flight from the Canadian Space Agency (CSA) launch facility in Timmins, Canada, inSeptember 2014. Preliminary analysis of the hyperspectral imagesindicates that the radiance measurements are of high quality, and wehave used these to retrieve vertical profiles of stratosphericaerosol extinction coefficient from 650 to 1000 nm, along withone moment of the particle size distribution. Those preliminaryresults are promising and development of a satellite prototype ofALI within the Canadian Space Agency is ongoing.