Multi-frequency VSOP and VLBI observations of the quasar 3C309.1

We present multi-frequency observational results for the Compact Steep-Spectrum (CSS) quasar 3C309.1. The observations were carried out with the VSOP at 1.6 and 4.8GHz and the VLBA at 15.4GHz. The source has a distorted, one-sided radio jet. Relativistics effects and physical properties are discussed. Comparing the predicted and observed X-ray fluxes in the framework of the synchrotron self-Compton model we derive the beaming factor for 3C309.1. The complex structure of the jet may be explained by a relativistic helical flow in a heterogeneous, clumpy ISM.