Space VLBI Observations Show [ITAL]T[/ITAL][TINF][ITAL]b[/ITAL][/TINF] ] 10[TSUP]12[/TSUP] K in the Quasar NRAO 530

We present here space-based VLBI observations with VLBI Space Observatory Program (VSOP) and a southern hemisphere ground array of the gamma-ray blazar NRAO 530 at 1.6 and 5 GHz. The brightness temperature of the core at 1.6 GHz is 5 × 10 11 K. The size is near the minimum observable value in the direction of NRAO 530 due to interstellar scattering. The 5 GHz data show a single component with a brightness temperature of ~3 × 10 12 K, significantly in excess of the inverse Compton limit and of the equipartition brightness temperature limit. This is strong evidence for relativistic motion in a jet requiring model-dependent Doppler boosting factors in the range 6-60. We show that a simple homogeneous sphere probably does not model the emission region accurately. We favor instead an inhomogeneous jet model with a Doppler boosting factor of 15.