Evaluation of Distributed System Mission (DSM) Architectures for Cloud Bow Retrievals using the Hyper-Angular Rainbow Polarimeter (HARP)

Abstract:

Clouds and aerosols have the largest influence on the Earth’s climate system, yet they contribute the largest uncertainties to estimates and interpretations of the global radiation budget. We can get the most information about aerosols and cloud particle properties from studying polarized observations taken at a wide range of different scattering angles. As such, polarimeters with multi-angular and multi-spectral capabilities enable the retrieval of cloud microphysical properties, such as cloud droplet size distribution (DSD). Traditional radiometric sensors are limited in their DSD retrievals since they can only infer cloud droplet effective radius (CDR), and not the distribution width (cloud droplet effective variance (CDV)). To overcome this limitation, and others, the Hyper-Angular Rainbow Polarimeter (HARP) CubeSat was designed with a multi-angular and multi-spectral pushbroom polarimeter that can see Earth from multiple viewing angles, wavelengths, and linear polarization states. However, there are still limitations in spatial and temporal coverage using just one HARP CubeSat that can be overcome via a constellation of HARP CubeSats. As part of this research study, orbit geometries for candidate distributed space mission (DSM) architectures were quantified for high quality cloud DSD retrievals using the cloud bow. In addition, statistical information from the orbits was collected to determine favorable observation geometries for dense angular sampling at scattering angles required for cloud DSD retrieval of liquid water clouds. Moreover, cloud bow retrieval sensitivity to HARP constellation geometry was determined. From this investigation an innovative observation strategy using a constellation of HARP CubeSats for cloud bow retrievals will be developed.