Halve melon, scoop out seeds and remove rind. Cut flesh into large chunks. (You should have about 6 cups.)
Working in batches if necessary, combine cantaloupe, honey and orange juice in a blender. Pulse or blend until smooth. Transfer to a large bowl, cover and refrigerate until thoroughly chilled, at least 2 hours.
Just before serving, briskly whisk soup and stir in mint. Serve very cold, garnished with sprigs of mint, if desired.