This data set contains meteorological measurements from the MASC-3 research UAS (unmanned aircraft system) during a measurement campaign in April and May 2018 in Ny-Alesund, Svalbard. This data provides high-resolution in-situ measurements of the three-dimensional wind vector, humidity, and temperature up to 600 m AMSL. The flight path of MASC-3 was along the Broggerdalen, 1 km west of Ny-Alesund. During a measurement, MASC-3 is controlled by autopilot and flies along a 1 km - 2km long path, turning at the ends and repeating this path multiple times in multiple altitudes. This data set only contains these straight sections (called flight legs), with all turns cut out and with a constant airspeed of 18.5 m/s. Wind measurement is done using a five-hole probe in the front of the aircraft, together with an Inertial navigation sytem (INS) to calculate the wind vector from the airflow relative to the aircraft.