Sea ice observations were routinely conducted by the Arctic and Antarctic Research Institute (AARI) group aboard AARI research vessel "Akademik Fedorov" during MOSAiC leg1 compaign, 25 September - 20 October 2019. Observations were conducted in accordance with AARI methodology. Special feature of the methodology is continuous estimation of sea ice parameters both along the track of navigation “on the route” (within the area around the ship of 2-3 widths of the hull) and “in the region” (within the range of eye visibility), with separation of recording into the zones with homogeneous ice characteristics [Manual on conduction of ice air reconnaissance / Rukovodstvo po proizvodstvu ledovoi aviarazvedki, 1981]. Observations were recorded in a form of an electronic log-book in accordance with the WMO Sea Ice Nomenclature (WMO-No.259) and WMO SIGRID-3 exchange format (SIGRID-3: A vector archive format for Sea Ice Georeferenced Information and Data - JCOMM TR-23, 2014).Column names, where applicable, correspond to SIGRID-3 naming convention for sea ice polygone field names (Tables A-2, B-2, B-3, C-2). Codes for the forms of ice fully correspond to SIGRID-3 "Table 3: Form of ice codes for variable identifiers FA, FB, FC, FP and FS".