Rinse out the blender. In a small saucepan, combine the orange juice with the remaining 1/2 cup of sugar and cook over moderate heat, stirring, until the sugar dissolves. Let cool completely. In the blender, puree the orange melon with the orange syrup. Freeze the puree in an ice cream maker according to the manufacturer's instructions. Pack the sorbet into another plastic container, press plastic wrap directly on the sorbet, cover and freeze.