Dec. 21 (UPI) -- NASA's Parker Solar Probe is operating normally and remains on schedule for a record-setting close encounter with the Sun on Christmas Eve, mission controllers say. All spacecraft systems on the probe are operating normally as it nears its closest point to the Sun at 3.8 million miles above the fiery solar surface, the Johns Hopkins Applied Physics Laboratory said in an update issued Friday. Advertisement "No human-made object has ever passed this close to a star, so Parker