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We present the development of SIR-HUXt, the integration of a sequentialimportance resampling (SIR) data assimilation scheme with the HUXt solar windmodel. SIR-HUXt is designed to assimilate the time-elongation profiles of CMEfronts in the low heliosphere, such as those typically extracted fromheliospheric imager data returned by the STEREO, Parker Solar Probe, and SolarOrbiter missions. We use Observing System Simulation Experiments to explore theperformance of SIR-HUXt for a simple synthetic CME scenario of a fully Earthdirected CME flowing through a uniform ambient solar wind, where the CME isinitialised with the average observed CME speed and width. These experimentsare performed for a range of observer locations, from 20 deg to 90 deg behindEarth, spanning the L5 point where ESA's future Vigil space weather monitorwill return heliospheric imager data for operational space weather forecasting.  We show that SIR-HUXt performs well at constraining the CME speed, and hassome success at constraining the CME longitude. The CME width is largelyunconstrained by the SIR-HUXt assimilations, and more experiments are requiredto determine if this is due to this specific CME scenario, or is a generalfeature of assimilating time-elongation profiles. Rank-histograms suggest thatthe SIR-HUXt ensembles are well calibrated, with no clear indications of biasor under/over dispersion. Improved constraints on the initial CME speed leaddirectly to improvements in the CME transit time to Earth and arrival speed.For an observer in the L5 region, SIR-HUXt returned a 69% reduction in the CMEtransit time uncertainty, and a 63% reduction in the arrival speed uncertainty.This suggests SIR-HUXt has potential to improve the real-world representivityof HUXt simulations, and therefore has potential to reduce the uncertainty ofCME arrival time hindcasts and forecasts.

SIR-HUXt -- a particle filter data assimilation scheme for assimilating CME time-elongation profiles