Volunteers are pulling on their Santa hats, phone lines are set, and tracking screens are ready — NORAD Tracks Santa is primed for its 57th annual goodwill mission. Santa trackers start taking calls today, telling children — and some adults — when Santa is due at their house. The last shift won't end until nearly 24 hours later. The number is 877-HI-NORAD or 877-446-6723. Updates will be posted online on Facebook and Twitter.