With the introduction of it's FlexBUS concept, Dornier Satellitensysteme GmbH has successfully entered the stage for small satellite development and manufacturing. Especially with its significant involvement in the engineering activities of the GFZ/DLR small satellite project CHAMP and the responsibility to lead the NASA/DLR GRACE project, a major step forward has been achieved in establishing Dornier as a major small satellite contractor.The CHAMP satellite (Challenging Mini-Satellite Payload for Geophysical Research and Application) of the GFZ (GeoForschungsZentrum Potsdam) is the first realized FlexBUS satellite. During its 5 year mission in a polar orbit, CHAMP will measure the magnetic field and the gravity field of the Earth as well as the state parameters of the atmosphere and the ionosphere. For this purpose CHAMP is equipped with various sensors such as a high resolution accelerometer, fluxgate and Overhauser magnetometers and a Digital Ion Drift Meter. For precise orbit determination a GPS receiver with 4 antennas, and a laser retroreflector are installed on the spacecraft. Atmospheric sounding is performed by interpreting the signals of occulting GPS satellites.2 pairs of star sensors provide high precision attitude information.In order to limit the cost of the project, already qualified components are used as far as possible. This affects also the complete test approach and in particular the thermal test program and the thermal testing of the satellite.On the other hand the satellite includes new developments for attitude measurement based on earth and sun vector determination by thermo-optical surfaces as well as a special foam insulation system.Within the paper the thermal verification approach with component and system level tests are presented. The preparation and performance of the TB/TV test with the different test modes and the test results are described.