Description: Large areas of the Arctic Ocean are covered with sea ice, the extent, thickness, concentration and properties of which change seasonally, interannually and on longer time scales. The Arctic Ocean is often difficult to access, making satellite remote sensing the only means to obtain information about the sea ice on a pan-Arctic scale. In order to improve the processing and interpretation of satellite data and imagery, in-situ calibration and validation are necessary. In spring 2011, measurements on first year sea ice north of Svalbard were performed during two scientific cruises with the ships KV “Svalbard” and RV “Lance” as a part of the CryoVEx 2011 project. During these cruises, detailed measurements of snow and ice thickness, freeboard, and snow density were performed on ice stations and from a helicopter. The data collected contributes to the calibration and validation of the SIRAL sensor data from the CryoSat-2 radar altimeter satellite, which measures the freeboard of sea ice for estimating its thickness. In snow pits, the stratigraphy of the snow pack was recorded. The collected data are currently being integrated with satellite data, airborne observations from helicopter that measured ice thickness using an electromagnetic induction sounder (EM-bird) and conducted aerial photography, and a Twin-Otter aircraft carrying the ESA Airborne Synthetic Aperture and Interferometric Radar Altimeter System (ASIRAS) system, the airborne radar altimeter designed to simulate the SIRAL radar on board the satellite, as well as a laser scanner. The first analysis of airborne and in- situ data indicates that the ASIRAS radar altimeter used in this experiment did not fully penetrate the snow layer on top of the sea ice. The regional sea ice characteristics for the research area are described using SAR products, obtained from the Envisat and Radarsat-2 satellites, in order to improve the interpretation and conclusions of the CryoSat-2 calibration and validation.