Rubidium Atomic Clock: The Workhorse of Satellite Navigation

317 Pages·2020·31.813 MB·English

by  G M Saxena, Bikash Ghosal

Rubidium
Atomic Clock
The Workhorse of Satellite Navigation
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Rubidium
Atomic Clock
The Workhorse of Satellite Navigation
G M Saxena
National Physical Laboratory, India
Bikash Ghosal
Space Applications Centre, India
World Scientific
NEW JERSEY • LONDON • SINGAPORE • BEIJING • SHANGHAI • HONG KONG • TAIPEI • CHENNAI • TOKYO
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British Library Cataloguing-in-Publication Data
A catalogue record for this book is available from the British Library.
RUBIDIUM ATOMIC CLOCK
The Workhorse of Satellite Navigation
Copyright © 2020 by World Scientific Publishing Co. Pte. Ltd.
All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means,
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ISBN 978-981-3279-48-3
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Desk Editor: Cheryl Heng
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I (GMS) am pleased to dedicate this book to my grand-daughter,
Ishika
(Daughter of Shilpi and Bhavya)
an inspiration for conceptualizing and writing this book
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Preface
Time is the most important part of human lives and their activities.
Since time immemorial, Time measurement remained in the central
stage of all kinds of measurements and underwent numerous and
far reaching changes. At present, different kinds of atomic clocks are
beingusedintelecommunication, digitalfinancialtransactions,space
explorations and many other applications. The satellite navigation
has become integral part of everyone’s life, as it helps in navigat-
ing to one’s destination, even in rainy days or dark nights, in thick
forests or advanced metropolis, with a precision of a few centimetres
to metres. All this could be possible because of the on-board Rubid-
ium (Rb) atomic clocks. To highlight the accuracy and stability of
th
theseRbatomicclocks,weshouldknowthataninaccuracyof1/100
of a Second may lead to a positional error of 30000km. So, for an
accuracy ofafewcms/metresinourdaytodayGPSguidedtravelby
cars or app based Taxis or in others scientific and commercial activ-
ities, the role of these Rb atomic clocks and their accuracy can be
appreciated. It is natural to ask how the highly accurate Time ticks
of the on-board atomic clocks help in achieving the precision in dis-
tance. Simple, at the heart of (Global Navigation Satellite System)
GNSS workings, is the fundamental relation among distance, light
velocity and time i.e., Distance = Velocity×Time. The Rb atomic
clocks have gained the place of pride in satellite navigation, because
of their light weight and small size, leaving behind several state-of-
the-art atomic clocks. These state-of-the-art atomic clocks could not
challenge Rb clock’s supremacy in the satellite navigation systems
like GPS, GLONASS, GALILEO, COMPASS and IRNSS. Most of
the on-board atomic clocks in these satellite navigation systems are
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viii Rubidium Atomic Clock: The Workhorse of Satellite Navigation
Rb atomic clocks. Itis rightly thedarlingandworkhorseof the satel-
lite navigation systems. In spite of being one of the earliest and the
oldest atomic clocks, researchers are still working on it, to unfold its
mysteries and improve its performance. All this sums up the intense
curiosity to explore, what is so special about this clock and as a
result bring about the conceptualization of this book. In the book,
history of time keeping and chronological development of clocks are
included. The Rb atomic clock is described including all its details
withspecialattention onitscritical part—thePhysicspackage. The
Physicspackagemainlydecidestheperformanceoftheclock.Nowsit
backandenjoyreadingabouttheRbatomicclock.Specialeffortsare
made to describe the Rb atomic clock in a simple way, to benefit the
maximum readership. This is perhaps,the only book of its kind,giv-
ing all the details of the Rb atomic clock in one place and one needs
not shuffle numerous papers and literature to get abridged informa-
tion on the clock. All in all, the researchers and the industrialists
interested in R&D and producing Rb atomic clocks, as a marketable
state-of-the-art product, will find the book very useful and practi-
cal. In the last chapter, the recipe for developing/manufacturing the
Rb atomic clock is given, that should be quite useful even for those
interested in developing the Rb atomic clocks for the first time.
G M Saxena
Bikash Ghosal
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Acknowledgement
With a great sense of gratitude, I (GMS) wish to express my regards
and appreciation for Prof B.S. Mathur, who introduced me to the
subject of optical pumping and Rb atomic clock. The free access to
him for the discussions on these complex subjects, is highly appre-
ciated. We are thankful to the present and the former Directors,
National Physical Laboratory, New Delhi India and SAC-ISRO, for
making it possible to do experimental R&D work on Rb atomic
clocks. This enriched our experience in the theoretical and exper-
imental aspects of the Rb atomic clock. The experience gained as
the leader (GMS) of CSIR-NPL and SAC-ISRO India collabora-
tive project on Rb atomic clock for IRNSS, helped in understand-
ing the stringencies of space qualification of the Rb atomic clock.
Dr Pardeep Mohan,Dr SS Verma,Mr A.Banik, MrSatender Singh,
Ms Savita Singh and SAC-ISRO scientists need special mention for
their contribution in the work on the Rb atomic clock. We thank-
fully,acknowledgetheinstitutions,laboratorieswhereweworkedand
gained wide-ranging experiences that helped immensely in conceptu-
alizing this book. The unclassified information on internet have been
used in this book and we sincerely acknowledge all those web sites
and their creators.
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