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HEWLETT-PACKARD
JOURNAL
T E C H N I C A L I N F O R M A T I O N F R O M T H E - h p - L A B O R A T O R I E S
Vol. 15, No. 11
IBLISHED BY THE HEWLETT-PACKARD COMPANY, 1501 PAGE MILL ROAD, PALO ALTO, CALIFORNIA JULY, 1964
A New Performance of the
"Flying Clock" Experiment
A new experiment has been made to compare clocks in the
U.S. and Europe to higher precision. The results will be
used by the various official agencies of the two continents
in improving their time synchronization.
J.HE PROBLEM of correlating the time of day at
widely separated locations with great accuracy
is one that has absorbed chronologists, navigators,
astronomers and cartographers for hundreds of
years. As vehicles grow faster and the range of
exploration reaches far into outer space, more
accurate time determinations become increasingly
necessary. Precise timing and coordination of
events far apart may determine the success of
precise mapping operations, satellite orbital place
ment, astronomical observations, or missile land
ings.
In recent years, intercontinental time of day
comparisons gradually reached an accuracy of
about one millisecond through use of h-f radio sig
nals, the limit being imposed by propagation-time
uncertainties of high frequency waves. Consider
ably higher accuracy is, however, possible. For ex
ample, two recent means have emerged to achieve
intercontinental time of day correlations with
accuracy of the order of a few microseconds.
Fig. 1. Data being logged in Switzerland at the Observa- One method has been to fly an accurate clock,
toire de Neuchatel by Alan S. Bagley of the -hp- Fre set precisely to a given time standard, from point
quency and Time Laboratories. Atomic clock in left fore
ground carried time to Switzerland aboard transatlantic to point, effectively bringing the time standard to
passenger flight.
each. U. S. government experiments have used
quartz oscillator-driven clocks as well as "atomic"
SEE ALSO. clocks in this manner. In 1960, for example,
Measuring (he ratio of Csm and Hydrogen, p. 6 Reder, Brown, Winkler, and Bickart, of the U. S.
Plan/ distribution o