This dataset contains raw observation data (Level 0) of dropsondes released from the High Altitude Long Range aircraft HALO over the North Atlantic during 15 research flights of the NAWDIC campaign in January and February 2026 (including a scientific test flight in December 2025). The raw data are stored in one CSV file per sonde (387 in total) that contains the decoded raw signals (time, GPS position, meteorological variables) recorded by the corresponding receiver channel of the KITsonde system. The file name indicates the start date and time of the decoded signal (before the release time), the number of the receiver channel (ch), and the unique 8-digit sonde identifier. One channel may be used multiple times per research flight when the system was re-started during the flight to accommodate all sondes.