The U.K. Met Office MSG dust product shows an estimation of the dust optical thickness retrieved from empirical relationship between SEVIRI infrared (10.8 µm) radiance and aerosol optical depth at 550nm.  It is generated by transforming original retrievals to regularly-spaced grids (0.18 degree) using simple average method.

WARNING: Some level of cloud contamination may exist in the MSGAOD product due to the lack of temporal differencing scheme in the cloud processing. These artefacts are predominant over the Sahel and southern latitudes.

The details of the retrieval can be read at the following articles:

Brindley, H. E., and J. E. Russell (2009), An assessment of Saharan dust loading and the corresponding cloud-free longwave direct radiative effect from geostationary satellite observations, J. Geophys. Res., Vol 114, 148-227.

Legrand, M.; Plana-Fattori, A.; N'doumé, C. (2001), Satellite detection of dust using the IR imagery of Meteosat 1. Infrared difference dust index, J. Geophys. Res., Vol. 106, 18251–18274.

An archive of this product can be found at SDS-WAS page.