The proposed project aims to develop new refined methods to obtain plasma environment parameters using spacecraft potential controlled by ASPOC instruments onboard the NASA MMS mission. The goal of the current project is to significantly enhance the accuracy of density estimation from spacecraft potential compared to  conventional methods applied in the previous MMS-ASPOC project by refining  techniques which take into account additional effects. These include DC and AC electric fields, asymmetry in the sheath and its spin-modulation stemming from streaming of plasma (wake effects) and from the ambient magnetic fields. The results shall be obtained both from analysis of MMS data including new plasma regions covered during the extension phase as well as from comparison with charging model data. The proposed new methods in this project are expected to significantly reduce the error of the density product. Furthermore, high time-resolution plasma data products will be obtained, including those from highly fluctuating field environment, which is important for studying electron-scale physics, i.e., one of the main objectives of the MMS mission.

The results will be disseminated by publication in scientific peer-reviewed journals and presentation in international meetings. Furthermore, newly developed refined density derivation methods together with data products will be made open to public. New knowledge is expected to further strengthen the expertise and competitiveness of IWF for ASPOC activities in future space plasma missions.