On Santa Claus's trail: one billion people will log on to track his progress

When Santa Claus leaves the North Pole to begin his epic delivery tomorrow, he will be tracked closely by radar and satellite, and by jet fighters following the sleigh. And this Christmas Eve there will be more men and women and boys and girls watching than ever, as the website showing his progress around the world in real time expects a billion hits.

"Norad Tracks Santa" run by the deadly serious North American Aerospace Defense Command has become a massive festive phenomenon. For one night only each year, the organisation set up to defend the US from incoming missiles sets its sights on Santa.

Originally an American craze, tracking Santa is rapidly picking up fans in this country and many others. Last year Jonathan Ross gave an excited commentary as the sleigh swooped over Big Ben, and broadcasters from other nations were also hired to describe Rudolph blazing across their night skies. This time the images from Santa Cams will be in 3D and the audience the largest yet, thanks to a link-up with the search engine Google.

At a retirement home in Colorado, a 90-year-old will follow the reindeer all the way. Harry Shoup is the man who started all this 52 years ago, after taking a very strange phone call. It's a remarkable story. "Oh my goodness, I'll never forget it," says Shoup. On 24 December 1955, he was colonel in charge of a massive radar system built to give the US early warning of the Soviet attack many people feared was imminent. The Cold War was at its height. The Pentagon was building nuclear missiles, the Kremlin doing the same. At his windowless base in Colorado Springs, in front of a massive three-storey map of the world that looked worryingly like the command room in Dr Strangelove, Colonel Shoup was keeping watch for Communist bombers.

"The red phone rang," he says. That never happened, and it meant huge trouble. The red phone was the emergency line: it could only be his commander calling, or the Pentagon. "I picked it up and I said: 'Yes, sir? This is Colonel Shoup.'"

There was no answer for a moment. Then came the hesitant voice of a small boy. "Are you really Santa Claus?"

Shoup was taken aback. "I looked around my staff and I thought, 'Somebody's playing a joke on me. This isn't funny.' I said, 'Would you repeat that, please?'" The boy asked again if he was Santa Claus. "I knew then that there was some screw-up on the phones."

There certainly was. A local Sears Roebuck store had advertised a Santa line, on which children could talk to the man himself as he prepared for his rounds. But the wrong phone number had been published. Instead of talking to a Sears volunteer, the child unwittingly got through to one of the most important lines in America and certainly to one of the most uptight men in the country that Christmas Eve.

Shoup called his workplace the Ulcer Palace because of the stress he was under there, according to his granddaughter Carrie Farrell. Now working for Google in California, she is telling her family story in full for the first time to The Independent on Sunday. "My grandfather was shocked at first," she says. "He was in no mood for this."

The colonel said no, he wasn't Santa and could he speak to the boy's mother? She came on the line and explained what had happened, at which point Ms Farrell says, "He started to lighten up. He was a very serious man ... but I think the season eventually got the better of him."

When the boy was told he had actually reached the radar command centre, he asked a question that would have massive implications for the base and for millions of children in the half-century to come. "Do you know where Santa is then?"

Colonel Shoup, laughing by now, decided to play along. He did have three young girls and a baby boy waiting at home, after all. So he spoke to the men who were mapping data on to the huge picture of the world. "They were able to find out where Santa was on the radar," says Ms Farrell. Really? "Oh sure," says the 36-year-old new technology expert, deadpan. "Yeah."

The red phone rang many times that night, and with each call, the radar team got more enthusiastic about this seasonal diversion from their ultra-serious work. "Everyone there went along with it," says Ms Farrell. The bosses did not, at first until Col Shoup convinced them it was a very good public relations tool for their new defence technology. "The guy comes off as being a bit hard on the outside, but he realised this was a chance for them to stand for something good."

The following Christmas the military actually advertised its ability to tell everyone where Santa was. Over the years a call to Norad became a part of the build-up to Christmas for many children in the US, but it remained an American secret until an internet version was launched in 1998.

In recent years the audience has grown fast. Last year the website now in five languages received 941 million hits from 210 countries. The phones were manned by 750 volunteers who took 65,000 calls and answered 96,000 emails. "My grandfather really does realise the scale of what this has become," says Ms Farrell. "He loves his legacy."

Her mother Pam, the middle of the three Shoup girls, was 11 in 1955. "They were taken to see the big screen," says Carrie. "They also got used to having reporters turn up every year."

Pam grew up to marry an air force pilot, who in time became commander of the air force academy at Colorado Springs. They had their own daughter, Carrie, who knew Christmas Eve as the time for Grandpa's ritual. "It was a family occasion with my grandfather at the helm. We would all sit there and he would tell us the story of Santa Claus, and his own personal story involving Santa."

Then he would get on the phone to the base commander. "We got the inside track. There was one set of information that was given to the public, but we got a little bit more information." They believed it too. "He was not kidding. When he told us we had to go to bed right away or Santa wouldn't come, then we did as we were told, because we knew he knew where Santa was."

This was a family in which the children loved science and maths puzzles and many of the adults knew how to fly so it was no great leap for her to get involved in the internet boom a decade ago. Ms Farrell has worked for Google since 2001, and now recruits engineers from an office in Manhattan, but surprisingly the link-up with Norad wasn't her idea. It came from one of those engineers who get to spend 20 per cent of their time on personal projects. "I hadn't told too many people about my grandfather until I heard about that."

This year Norad will use the Google Earth application which allows users to zoom in on a realistic landscape anywhere in the world, assembled using satellite photographs and overlaid with information. Tomorrow that will include Santa's sleigh as it moves through the sky.

Norad starts tracking at 9am British time, when it is expected he will still be at the North Pole. His route changes from year to year, but always involves starting after sunset somewhere around New Zealand.

Traditions vary: here, most people expect Santa around midnight, but in some countries such as Argentina, Sweden and Germany the presents have to arrive on Christmas Eve itself. That makes for a complicated journey, but by flying west from the Antipodes, Santa can pass through different time zones and give himself at least 24 hours to make the deliveries to an estimated 75 million homes.

There are many theories about how he does it. The sceptics say you would need 214,200 reindeer (assuming you had some that could fly) travelling at 650 miles per second, which would cause them to burn up in the sky like a meteorite. But scientists love to show that it's all possible: the astrophysicist Knut Jorgen Roeed Odegaard from Norway says the heat should be no problem if Santa has "an ion-shield of charged particles, held together by a magnetic field, surrounding the sleigh".

At North Carolina State University, Dr Larry Silverberg is a professor of mechanical and aerospace engineering. He says Santa is a super-scientist who travels in a "relativity cloud" that makes the rest of the world appear frozen in a moment and gives him all the time he needs.

"Based on his advanced knowledge of the theory of relativity, Santa recognises that time can be stretched like a rubber band, that space can be squeezed like an orange and that light can be bent," says Dr Silverberg. "Relativity clouds are controllable domains rips in time that allow him months to deliver presents while only a few minutes pass on Earth. The presents are truly delivered in a wink of an eye."

As for Norad, it has as little time for sceptics as it once had for Soviets. "The fact that Santa Claus is more than 15 centuries old and does not appear to age is our biggest clue that he does not work within time as we know it."

It will track him using 47 radar installations along the northern border of North America, and orbiting satellites that use infra-red to detect launched missiles or Rudolph's glowing nose. There are also Santa Cam digital cameras at key locations around the world, and Canadian CF-18 fighters to escort the sleigh through North American airspace.

Harry Shoup, who lives "right across the street" from the air force academy, likes to wear a shirt that says "Santa's Colonel". "He is so excited. He will be tracking Santa, same as always," says his granddaughter.

She won't, though. Carrie Farrell will be on a plane flying to Australia. "There's a good chance I will look out of the window and see Santa in flight. That is exactly what I expect to happen." She says it with such conviction, just like Col Shoup shooing his excited children and so many around the world to their beds.

Further browsing If you want to track Santa's journey, go to noradsanta.org