The Hunga volcano violently erupted on 15 January 2022, producing the largest perturbation of the stratospheric aerosol layer since Pinatubo 1991, despite the initially estimated modest injection of SO₂. This study presents novel SO₂ and sulfate aerosol (SA) co-retrievals from the Infrared Atmospheric Sounding Interferometer, and uses them to quantify the initial progression of the Hunga plume. These observations are consistent with rapid conversion of SO₂ (e-folding time: 17.1 ± 4.3 days) to SA, with an injected burden of >1.0 Tg SO₂. This points at larger SO₂ injections than previously thought. A long-lasting SA plume was observed, with two separate build-up phases, and with a meridional dispersion of marked anomalies from the tropics to the higher southern hemispheric latitudes. A limited (∼20%) SA removal was observed after 1-year dispersion. The total injected SA mass burden was estimated at 1.6 ± 0.5 Tg in the total atmospheric column, with a build-up e-folding time of about 2 months.