Te concentration in GaSb grown under microgravity was measured by spatially resolved photoluminescence (SRPL). For this purpose, a calibration curve is experimentally obtained to give a relationship between Te concentration and PL energy. It was found that after the growth starts the Te concentration drops at the melted and unmelted interface and recovers rapidly to the level of the initial concentration which means that the distribution is close to that of pure diffusion control. Three possible shapes of the GaSb melt in space were postulated and it is suggested that a wide free surface existed on the GaSb melt during growth. The reason for the absence of strong Marangoni flow is attributed to either the small temperature difference across the free surface or to the presence of a thin oxide film on the melt.