  Emissions of particulate matter into the atmosphere are essential to
characterize, in terms of properties such as particle size, morphology, and
composition, to better understand impacts on public health and the climate.
However, there is no currently available technology capable of measuring
individual particles with such high detail over the extensive domains
associated with events such as wildfires or volcanic eruptions. To solve this
problem, we present an autonomous measurement system involving an unmanned
aerial vehicle (UAV) coupled with a digital inline holographic microscope for
in situ particle diagnostics. The flight control uses computer vision to
localize and then trace the movements of particle-laden flows while sampling
particles to determine their properties as they are transported away from their
source. We demonstrate this system applied to measuring particulate matter in
smoke plumes and discuss broader implications for this type of system in
similar applications.
