Trying to Get Somewhere? An Atomic Clock May Be Helping. – The New York Times

A satellite circling 14,000 miles over your head has some news for you: There is nothing like an atomic clock to get you to your precise destination both on time and, well, to your precise destination.

Most of us rarely think about how that GPS on our smartphone tells us where to go or how that airplane we are snoozing on gets us to our destination. We have come to accept global movement as something like the proverbial pin in a map. But what would a clock have to do with that?

At Leonardo, the Italian aerospace company that created the hydrogen atomic clocks for the first generation of 26 Galileo satellites that float over the planet working like celestial traffic cops, the scientists have some answers.

This past summer, the European Commission and the European Space Agency selected that first-generation clock, officially called the Passive Hydrogen Maser, for the second generation of 12 Galileo satellites. They will form the European Unions official satellite navigation system, and the newest additions are to be delivered starting in 2023. Each satellite is designed to last about 12 years.

From the companys perspective, atoms keeping time in the heavens is not unlike timekeeping throughout history. It is just that now humans move much faster, and expect all-but-instant gratification as well as precision.

Navigating the high seas at onetime required looking at the sun, the moon and the planets before scientists started developing better and better clocks, Jacopo Belfi, a system engineer for atomic clocks at Leonardo, which is based in Rome, said in a recent phone interview.

The 18th-century invention of the marine chronometer, a specific type of highly accurate mechanical timepiece, helped determine the longitude of a vessel by comparing the positions of the stars to the time on the chronometer (set to Greenwich Mean Time for most oceangoing vessels by the late 19th century), and calculating how far it had traveled east or west. (Latitude had long been determined by tracking the suns position at high noon, or when it reached its highest point.)

Fast-forward to the early 21st century. With the need for more precision and beginning of GPS, the only way to create the exact position was to use an atomic system because at the microscopic level it provides oscillation, almost like perfect little pendulums, Mr. Belfi said. An atomic clock doesnt suffer because of the changes in temperature or the movement of a ship or the humidity or atmospheric pressure.

The company said that more than two billion users relied on the Galileo satellites, which, along with other global navigation systems, measures the physical distance and the time difference between the receiver and the satellite. It pinpoints the users position, the time and the speed by gathering data from four satellites: three to determine the coordinates of the users position and a fourth for time.

The moment that you connect to your device, you receive a message from a satellite at the speed of light, and therefore the distance is measured by both speed and time, said Marina Gioia, integrated project team leader for atomic clocks at Leonardo. The receiver and the satellite need to be synchronized by time. An error of one millionth of a second would mean a positioning error of up to 300 meters (about 1,000 feet). But the accuracy of these clocks allows Galileo to guarantee a precision of 30 centimeters.

This need for precision is critical, and the Passive Hydrogen Maser boasts an error of only one billionth of a second per day, or one second every three million years, according to Leonardo. These are mind-bending numbers for those of us going about our daily business with little comprehension of all the scientific drama.

We take for granted satellite positioning, but what would happen if these signals were turned off? Ms. Gioia asked. Aircraft, shipping, trucks, finance, communication, public utilities, emergency services, agriculture they all rely on exact positioning.

The Passive Hydrogen Maser, which measures less than 2 feet long and weighs about 40 pounds, looks more like a high-tech science class creation than a conventional clock. But its insides are where the precision exists, which also has a connection to the heavens, from Mr. Belfis perspective.

The typical image is that the atom is a planetary system and that the charged nucleus has the same role of the sun, and the electrons are the planets orbiting around it, he said. The laws of physics make the atom the perfect timekeeper.

Now, on the heels of its contract with Galileo, Leonardo has been showing off its newest clock at the Italy Pavilion in the Dubai Expo 2020 (which runs through March).

It is the RbPOP, shorthand for rubidium pulsed optically pumped a rubidium atomic clock developed by the company in partnership with the National Institute of Meteorological Research in Italy. (Rubidium is a soft and absorbent metal, which allows its atoms to be more easily manipulated than other metals or substances.)

It weighs about 22 pounds, or about half that of the Passive Hydrogen Maser. While its main use has not been determined yet, it certainly will be involved in future space missions, the company said.

But here on Earth, the focus is making sure billions of people get from point A to point B with the most accurate atomic clocks possible.

If the time of the satellite is not precise, Ms. Gioia said with a laugh, you will end up at the grocery store instead of the beach.

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Trying to Get Somewhere? An Atomic Clock May Be Helping. - The New York Times