COLORADO SPRINGS, COLO. ? The North American Aerospace Defense Command is the joint U.S.-Canadian agency responsible for protecting the continent’s skies from foreign threats.

This time of year, NORAD is busy with something even more important than national defense: tracking the progress of Santa and his reindeer-driven sleigh across the heavens on Christmas Eve.

Maj. Doug Martin of the Canadian army is managing the activity this year. It has grown into a big job, indeed. Last year, NORAD’s Santa-tracking Web site received 289 million hits. There is no other site in the world that details where Santa is to be found Christmas Eve in full living color and in English, French, Spanish, Portuguese, Italian, and Japanese.

More than 200 volunteers fielded 7,000 phone calls from callers last Christmas, and responded to 27,000 e-mails. This year, the number of volunteers has swelled to 375, all military personnel and their families, who will spend almost 24 full hours answering questions such as “How does he get down all those chimneys?” and “How fast does he fly, anyway?”

“We’d love to know the answer — we know it’s at least mach 30, or 30 times the speed of sound — but many details of Santa’s flights are classified,” Martin says.

Sometimes there are problems. In blizzard-like conditions, the 25 special cameras NORAD says it’s placed around the world to photograph Santa have gone blank. “We’ve lost him, yeah, but we don’t like to talk about it,” Martin says.

“Keep in mind this guy flies at the twinkle of an eye. Blink and he’s gone,” adds Army Maj. Barry Venable.

If Rudolph the reindeer has a cold, sometimes the red light on his nose has been known to go out, making it impossible for U.S. military satellites, equipped with infrared sensors, to track Santa’s team. Also, the temperature of Rudolph’s nose can affect satellite sensing, Venable explains.

Look directly at Rudolph at night and “you’ll lose your night vision: that bright red light is just too intense,” says Maj. William Routt, a F-15C fighter pilot with more than 2,000 flight hours under his belt.

The last time he accompanied Santa and his reindeer on a test run — NORAD says it sends up a fighter jet escort every year — “I was doing mach 1.1 and he left me in the dust,” Routt says.

All this began as an accident 47 years ago, when a local Sears store published a wrong number in a newspaper ad inviting kids to call Santa. The number in the paper was actually a hotline at NORAD.

When a colonel picked up the phone expecting a general on the other end in December 1955, a 6-year-old boy asked to talk to Santa instead.

Yes, our radar does show something. Yes, it’s Santa, the quick-thinking colonel told the boy, and you’d better go to bed before he comes. More calls came in, and a NORAD tradition was born.

“When you think about it, tracking and protecting Santa is mission accomplished for NORAD, because what we’re really about is preserving the peace every day of the year, but particularly on Christmas,” Venable says.

To which Americans may well want to say amen.