Page 10 - trends in automation

First-hand information:

Interview

with Prof. Dr. Joachim H. Ullrich.

About the person

Prof. Dr. Joachim Ullrich

Joachim Ullrich has been President of the Physikalisch-

Technische Bundesanstalt (PTB), Germany’s national me-

trology institute, based in Braunschweig since 2012. Prior

to that, he was was Director of the Max Planck Institute

for Nuclear Physics in Heidelberg and headed up the

Experimental Few-Particle Quantum Dynamics division.

He is internationally renowned not only as President of

the National Metrology Institute, but also as an expert

in quantum physics and experiments with free-electron

lasers carried out at DESY in Hamburg and the SLAC

National Accelerator Laboratory in Stanford, USA. He has

received numerous awards for his work, including the

Gottfried Wilhelm Leibniz Award of the German Research

Foundation (DFG) and the Philip Morris Research Prize.

www.ptb.de

at the time. Researchers discovered that the earth’s rotation is

slowing down and highly variable and doesn’t always move at

the same speed, as had been the assumed for the existing

definition of time.

Are there also practical applications for atomic clocks?

Ullrich:

Atomic clocks are used by the positioning satellites for

the American GPS system or the Russian GLONASS, for example,

as well as for the first satellites of the European Galileo system.

These systems identify locations using signal running times

between the satellite and the earth and therefore need very

precise time specifications. There are also plans to use clocks

for measurement in space in the near future. This will allow

highprecision measurement of the relative position of two

satellites and their change can be used to fully plot the earth’s

gravitational field. With similar measurements on the earth and

even more accurate clocks, it may even be possible to detect

different mass distributions and thus trace mineral resources in

the future. These are the kinds of topics that we are currently

working on with other researchers in the QUEST excellence

cluster at the Leibniz University of Hanover.

Do the clocks on the satellites have the same complex

structures as the atomic clocks of the PTB?

Ullrich:

They work according to the same principle, but are

slightly more compact and don’t have to be quite as accurate.

The previous signal transmission results in minor deviations in

any case. Atomic clocks can be easily acquired nowadays for a

wide variety of uses. They cost between a few hundred and

around 100,000 euros for earth-based applications. For satellite

applications they are significantly more expensive – and thanks

to sophisticated technology can generally run for many years

without any maintenance.

You say that the technology is sophisticated. However,

can an atomic clock such as the one here at the Physikalisch-

Technische Bundesanstalt fail?

Ullrich:

Of course that is a possibility, but we have back-ups.

In our institute alone we have four primary atomic clocks tick-

ing away as our contribution to Coordinated Universal Time.

To provide the time for radio clocks, for example, which is

transmitted from Mainflingen, near Frankfurt, using a long-

wave transmitter, there are a further three atomic clocks on

site, which are regularly synchronised with our clocks.