IRIS Mg II SJ image recorded at 08:40:16 UT (upper left panel) co-aligned by default with the AIA 304 Å channel image obtained at 08:40:19 UT (upper right panel). In the lower left panel is the AIA 211 Å channel image from 08:40:12 UT and in the lower right panel is the KSO Hα filtergram recorded at 07:32:01 UT; both these images are co-aligned with the IRIS observations. Structures visible in the Hα line resemble well the darkest absorption features present in the AIA 211 Å image. The IRIS FOV, the area of possible SUMER slit occurrence within uncertainties, and the analyzed area of the prominence – that is the section along the solar_Y, from which data were taken for the analysis – are marked in all four images.