Ionospheric Data Assimilation of Ultraviolet Photometer Data for the Coordinated Ionospheric CubeSat Experiment (CIRCE)

The upcoming Coordinated Ionospheric Reconstruction CubeSat Experiment (CIRCE) will investigate space weather in the ionosphere-thermosphere system using a suite of remote sensing and in situ instruments. CIRCE will provide multi-point measurements from two 6U CubeSats flying lead-trail in the same orbital plane, using ultraviolet photometers to generate tomographic reconstructions of the ionosphere. The UV data from CIRCE is planned to be operationally ingested into NextGen Ionosphere for Military Operations (NIMO) model that uses SAMI3 as a background and IDA4D 3DVAR scheme for the assimilation. As for many other data sources, there are many different approaches to the ingestion of the UV data. For example, a tomographic inversion can be performed first to obtain the point density measurements (that can further be ingested into IDA4D), or raw UV data from multiple channels can be ingested simultaneously into IDA4D 3DVAR algorithm. This study performs an OSSE and compares different approaches to the assimilation of UV data. The previously developed tomographic inversion is compared to sequential Kalman filter preprocessing inversion, and to a particle filter assimilation scheme.