Two-Way Satellite Time Transfer: Overview and Recent Developments

Two-Way Satellite Time Transfer: Overview and Recent Developments
Author: Gerrit De Jong
Publisher:
Total Pages: 17
Release: 1993
Genre:
ISBN:
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The experiment using small earth stations for transatlantic two-way satellite time transfer between the USA (USNO, Washington, DC) and Germany (DFVLR), Oberfaffenhofen) has had its 10th anniversary this year. Pseudo Random Noise coded time signals were phase modulated and demodulated at each stations using a modem developed by Professor Hartl and his staff. Recently, during the last two weeks of August 1993, six European time laboratories have used the INTELSAT 307E satellite for line-up tests and preliminary time transfer sessions using the same type of MITREX modem. This opportunity was given by INTELSAT, thanks to the help of Dr. Veenstra. The need for a uniform format for the exchange of data was felt heavily after these sessions. This problem was foreseen and addressed in international working parties. During April 1993 in Task Group 712 of the ITU Radiocommunication Sector (formerly CCIR), a very intense discussion has taken place about what procedures should be recommended for TWS TFT and what items the header and data lines of the resulting data fields should contain. A difficulty is that two different methods of calibration of the earth station delays exist which results different sets of delay data to be exchanged. Further study and discussions are necessary. Also, a meeting of the CCDS Working Group on TWSTFT addressed this in October 1993. The outcome of the discussions and the prospect for future developments will be presented.

Satellite Two-Way Time Transfer: Fundamentals and Recent Progress

Satellite Two-Way Time Transfer: Fundamentals and Recent Progress
Author:
Publisher:
Total Pages: 14
Release: 1989
Genre:
ISBN:
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Experiments in precise clock comparisons using the two-way time transfer technique via satellite began in 1962. Experience gained from a variety of experiments since that time steadily improved the precision and accuracy of such comparisons. Recent growth in the fixed satellite service, or FSS, has created new opportunities at moderate costs for high-accuracy time transfers using geostationary satellites. We discuss fundamental aspects of two-way timing and show an implementation of a satellite two-way time transfer system which has been used for two-years between USNO, Washington, D.C. and NIST, Boulder, CO. The raw data collection procedure will be discussed. We also outline the rationale for the choice of satellite uplink/downlink frequencies, signal structure, and reduction of data. Short-term noise in the time transfer limits the precision to about 300 ps in a 300 s average. Uncertainty in accuracy is due to uncertainty in the non-reciprocity of the two-way signal path. Accuracy limits due to the atmosphere, earth-satellite rotating system (Sagnac effect), and the equipment are discussed. The goal is to achieve an accuracy level of 1 ns after a suitable calibration of earth-station (differential) equipment delays.

Development of Carrier-Phase-Based Two-Way Satellite Time and Frequency Transfer (TWSTFT).

Development of Carrier-Phase-Based Two-Way Satellite Time and Frequency Transfer (TWSTFT).
Author:
Publisher:
Total Pages: 17
Release: 2005
Genre:
ISBN:
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For the dissemination of precise time and frequency, the use of the Two-Way Satellite Time and Frequency Transfer (TWSTFT) method has, in recent years, become increasingly valuable. By the application of spread-spectrum technology, a client station, located anywhere within a common satellite s footprint, can link to a reference station and compare or synchronize its clock to the reference clock within nanoseconds or better with high levels of confidence. But as the frequency stabilities of today's sophisticated atomic-level clocks improve, so must the stability of a Two-Way system s method of time and frequency transfer. Carrier-phase information holds the promise of improving the stabilities of TWSTFT measurements, because of the great precision at which frequency transfers can be achieved. The technique requires that each site observe both its own satellite-translated signal and that of the cooperating site. As was reported in earlier papers, the translation frequency of the satellite itself is an additional unknown factor in the measurement, and it must be taken into consideration. However, it can be shown that simple estimates of the satellite s local oscillator (LO) frequency will suffice. Recent work has been conducted with implementation of the signal carrier-phase in operational TWSTFT links. The purpose of this paper is to discuss this recent work, with emphasis on the system's development.

An Introduction to Modern Timekeeping and Time Transfer

An Introduction to Modern Timekeeping and Time Transfer
Author: Parameswar Banerjee
Publisher: Springer Nature
Total Pages: 312
Release: 2023-10-01
Genre: Technology & Engineering
ISBN: 3031307801
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This book provides a comprehensive, systematic description of modern timekeeping and its specializations. Introductory chapters discuss the concept of time and its definition, then briefly look at pre-Atomic Era timekeeping to set the stage for the introduction of the atomic clock. Subsequent chapters focus on concepts such as frequency stability and measurement uncertainty, as well as computer network time-synchronization protocols including Network Time Protocol (NTP) and Precise Time Protocol (PTP). The book then delves into the nuts and bolts of the Global Navigation Satellite Systems (GNSS), Two-Way Satellite Time and Frequency Transfer, and Optical Time and Frequency Transfer. Timescale theory is then described as a way to combine clock data, and the algorithms and procedures used to generate Coordinated Universal Time (UTC) are given. Finally, there is a look at modern applications of timekeeping and time transfer. Featuring a glossary of all key terms, this book is highly recommended for trained or incoming physicists, engineers, or mathematicians working, for example, in manufacturing or timing laboratories. Additionally, it is suitable for use in introductory university courses dealing with the subject of timekeeping.

Recent Advances in Metrology

Recent Advances in Metrology
Author: Sanjay Yadav
Publisher: Springer Nature
Total Pages: 225
Release: 2023-10-03
Genre: Technology & Engineering
ISBN: 9819945941
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This book presents the select proceedings of the 11th National Conference on Advances in Metrology (AdMet 2022). The book highlights and discusses the recent technological developments in the areas of fundamental and quantum metrology, physico-mechanical and electrical metrology, time and frequency metrology, materials metrology, industrial and legal metrology, digital transformation in metrology, among others. This book is aimed for those engaged in conformity assessment, quality system management, calibration, and testing in all sectors of industry. The book is a valuable reference for metrologists, scientists, engineers, academicians, and students from research institutes and industrial establishments to explore the future directions and research in the areas of sensors, advance materials, measurements, and quality improvement.

Handbook of Metrology and Applications

Handbook of Metrology and Applications
Author: Dinesh K. Aswal
Publisher: Springer Nature
Total Pages: 2504
Release: 2023-08-23
Genre: Technology & Engineering
ISBN: 9819920744
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​This handbook provides comprehensive and up-to-date information on the topic of scientific, industrial and legal metrology. It discusses the state-of-art review of various metrological aspects pertaining to redefinition of SI Units and their implications, applications of time and frequency metrology, certified reference materials, industrial metrology, industry 4.0, metrology in additive manufacturing, digital transformations in metrology, soft metrology and cyber security, optics in metrology, nano-metrology, metrology for advanced communication, environmental metrology, metrology in biomedical engineering, legal metrology and global trade, ionizing radiation metrology, advanced techniques in evaluation of measurement uncertainty, etc. The book has contributed chapters from world’s leading metrologists and experts on the diversified metrological theme. The internationally recognized team of editors adopt a consistent and systematic approach and writing style, including ample cross reference among topics, offering readers a user-friendly knowledgebase greater than the sum of its parts, perfect for frequent consultation. Moreover, the content of this volume is highly interdisciplinary in nature, with insights from not only metrology but also mechanical/material science, optics, physics, chemistry, biomedical and more. This handbook is ideal for academic and professional readers in the traditional and emerging areas of metrology and related fields.