This work compares transient measurements of flame growth and temperature field with a one-dimensional numerical model of an expanding spherical diffusion flame in microgravity. The purpose of this work is to study fundamental characteristics of flame extinction induced by gas radiation. In particular, the effects of various diluents with different radiative properties on the flame quenching mechanism are investigated. Experiments were conducted at atmospheric pressure using a porous spherical burner aerodynamically supporting an ethylene diffusion flame in an oxidizing atmosphere. A color CCD camera was used for visual observations and to obtain the flame growth rate. Temperature field was measured by an array of thermocouples that were corrected for heat transfer. The numerical model is based on a finite difference method in onedimensional spherical coordinates for steady and unsteady flames with consideration of detailed chemistry and transport properties. This work is a step toward the development and validation of a numerical model to understand the interaction between flame radiation and chemistry especially at extinction of microgravity diffusion flames.