In preparation to the launch of the SAGE III experiment in March 2001, NASA and the European Union performed the SOLVE/THESEO-2000 campaign, which had three components: (i) an aircraft campaign using the NASA DC-8 and ER-2 airplanes out of Kiruna/Sweden, (ii) launches of large stratospheric research balloons from Kiruna, (iii) validation exercises for the commissioning phase of SAGE III. The German Arctic research station Koldewey in Ny-Ålesund/Spitsbergen contributed to (i), (ii), and (iii) by performing measurements of stratospheric components like ozone, trace gases, aerosols (PSCs), temperature and winds. The main observation periods were from December 1999 to March 2000.