Coordinated Universal Time Research Articles

The Future of Time: UTC and the Leap Second

Before atomic timekeeping, clocks were set to the skies. But starting in 1972, radio signals began broadcasting atomic seconds and leap seconds have occasionally been added to that stream of atomic seconds to keep the signals synchronized with the actual rotation of Earth. Such adjustments were considered necessary because Earth's rotation is less regular than atomic timekeeping. In January 2012, a United Nations-affiliated organization could permanently break this link by redefining Coordinated Universal Time. To understand the importance of this potential change, it's important to understand the history of human timekeeping.

Investigation of trends in synoptic patterns over Europe with artificial neural networks

Abstract. The present study is a comprehensive application of a methodology developed for the classification of synoptic situations using artificial neural networks. In this respect, the 500 hPa geopotential height patterns at 12:00 UTC (Universal Time Coordinated) determined from the reanalysis data (ERA-40 dataset) of the European Centre for Medium range Weather Forecasts (ECMWF) over Europe were used. The dataset covers a period of 45 years (1957–2002) and the neural network methodology applied is the SOM architecture (Self Organizing Maps). The classification of the synoptic scale systems was conducted by considering 9, 18, 27 and 36 synoptic patterns. The statistical analysis of the frequency distribution of the classification results for the 36 clusters over the entire 44-year period revealed significant tendencies in the frequency distribution of certain clusters, thus substantiating a possible climatic change. In the following, the database was split into two periods, the "reference" period that includes the first 30 years and the "test" period comprising the remaining 14 years.

High-Speed Spectrographic Photometry of the Stardust Sample Return Capsule Around Peak Deceleration

The descent of the Stardust Sample Return Capsule on 15 January 2006 was observed with an intensified highframe-rate slitless spectrograph, which was operated in staring mode. Spectra were recorded at 300 frames per second from 09:57:47 to 09:57:57 UTC (Coordinated Universal Time), around the time of peak deceleration of the capsule. At this time, the spectra contained continuum emission from the hot surface and appeared to be featureless otherwise, with the exception of the telluric absorption caused by molecular oxygen in the atmosphere between the capsule and the observer. By averaging all spectra together, however, it was possible to bring outweak emission lines of oxygen and potassium over the time frame 09:57:51–54 UTC and sodium emission during 09:57:48–51 UTC. The spectral sequence was analyzed for signs of variation in the total emission from a possible wobbling of the capsule at periods higher than the spin rate. No such variationwas observed above the detection threshold of 5 amplitude in the line of sight.

Variability of meteorological elements shaping biometeorological conditions in Szczecin, Poland

In this study, the time and spatial variability of perceptible conditions, determined on the basis of effective temperature in the area of the Szczecin agglomeration are presented. The study was based on air temperature, relative humidity and wind speed data acquired during 2005–2007 from three emissions stations located in the centre and on the outskirts of the city of Szczecin, Poland. The differences in the values of the measured meteorological components between the studied city locations, in terms of their magnitude and daily structure, were analysed by month and calendar season. The results demonstrate that the temperatures in the city centre were considerably higher throughout the daily cycle, which was most evident during the summer in contrast to winter when the differences were the lowest. Mainly June and July, at 17–24 UTC (Coordinated Universal Time), were characterized by the average highest intensity of the urban heat island. Reduced relative humidity in the centre of Szczecin, as compared to the suburban areas, was observed particularly during summer. Throughout the daily cycle, this trend was also observed during spring, primarily during the night. Wind speed within the congested housing in the centre of Szczecin was over two-fold lower as compared to the unbuilt-up areas of the outskirts, irrespective of the time of the day and season of the year. Modification of the air humidity, thermal and anemometric conditions was reflected in a considerable variation in heat perception. In summer and spring, between 1300 and 2100 UTC, the most burdening biometeorological conditions, sensed as ‘hot’ and ‘very hot’ weather, prevailed in the city centre. During winter, on the other hand, the unbuilt-up areas on the city outskirts were the most unfavourable in terms of biothermal conditions, with the predominant categories of perceptible weather conditions throughout the daily cycle being ‘cold’ and ‘very cold’.

Simultaneous and multiple EAS Events due to the Gerasimova-Zatsepin Effect with the LAAS Experiments

We have measured extensive air showers (EAS) with primary cosmic ray energies above PeV at multiple EAS observatories deployed in Japan since 1996. Each array has been located on the rooftops of buildings in the university campus, and has a GPS-disciplined 10 MHz oscillator to provide UTC time stamps for each EAS event with microsecond accuracies. We have carried out a search for simultaneous and parallel EAS events at multiple EAS sites, such as Gerasimova-Zatsepin events, by comparing the EAS arrival time stamp and directions between long baseline EAS arrays. We selected EAS pairs for which the time difference and angular distance were less than 15 ° and 5 msec respectively and then examined the angular distances of these events from the solar and lunar directions. Consequently, we conclude that we do not find any excesses of these events in the solar direction so far, as expected in the theoretical prediction of GZ effects. We found deficiencies of EAS pairs in the lunar direction, but its deviation is not significant.

Fractional Feynman-Kac Equation for Non-Brownian Functionals

We derive backward and forward fractional Feynman-Kac equations for the distribution of functionals of the path of a particle undergoing anomalous diffusion. Fractional substantial derivatives introduced by Friedrich and co-workers [Phys. Rev. Lett. 96, 230601 (2006)10.1103/PhysRevLett.96.230601] provide the correct fractional framework for the problem. For applications, we calculate the distribution of occupation times in half space and show how the statistics of anomalous functionals is related to weak ergodicity breaking.

Combination of TWSTFT and GNSS for accurate UTC time transfer

The international UTC/TAI time and frequency transfer network is based on two independent space techniques: Two-Way Satellite Time and Frequency Transfer (TWSTFT) and Global Navigation Satellite System (GNSS). The network is highly redundant. In fact, 28% of the national time laboratories, which contribute 88% of the total atomic clock weight and all the primary frequency standards to UTC/TAI, operate both techniques. This redundancy is not fully used in UTC/TAI generation. We propose a combination that keeps the advantages of TWSTFT and GNSS and offers a new and effective strategy to improve UTC/TAI in terms of accuracy, stability and robustness. We focus on the combination of two BIPM routine products, TWSTFT and GPS PPP (time transfer using the precise point positioning technique), but the proposed method can be used for any carrier phase-based GNSS product.

COMPOSITION AND SPECTRAL PROPERTIES OF THE 1 AU QUIET-TIME SUPRATHERMAL ION POPULATION DURING SOLAR CYCLE 23

We have surveyed the spectral and compositional properties of suprathermal heavy ions during quiet times from 1995 January 1 to 2007 December 31 using Wind/Energetic Particles: Anisotropy, Composition, and Transport/SupraThermal-through-Energetic Particle Telescope and Advanced Composition Explorer/Ultra-low Energy Isotope Spectrometer at energies between 0.04 and 2.56 MeV nucleon–1. We find the following. (1) Quiet-time Fe/O and C/O abundances are correlated with solar cycle activity, reflecting corresponding values measured in solar energetic particle and interplanetary (IP) shock events during solar maximum, and those measured in the solar wind and corotating interaction regions (CIRs) during solar minimum conditions. (2) The 3He/4He ratio lies in the 3%-8% range during the quiet times of 1998-2004 with finite 3He detected on ~27.4% of the days. This ratio drops to 0.3%-1.2% during 2005-2007 and finite 3He is detected on ~5% of the days. (3) All heavy-ion species exhibit suprathermal tails between 0.04 and 0.32 MeV nucleon–1 with spectral indices ranging from ~1.27 to 2.29. These tails sometimes extend above ~2 MeV nucleon–1 with Fe spectra rolling over at lower energies than those of CNO. (4) The suprathermal tail spectral indices of heavier species (i.e., Fe) are harder than those of the lighter ones (i.e., CNO). These indices do not exhibit a clear solar cycle dependence and for ~50% of the time, they deviate significantly from the 1.5 value. These compositional observations provide evidence that even during the quietest times in IP space, the suprathermal population (3He and C-through-Fe) consists of ions from different sources whose relative contributions vary with solar activity. The heavy-ion energy spectra exhibit suprathermal tails with variable spectral indices that do not exhibit the spectral index of 1.5 predicted by some recent models.

통신위성 이용 멀티채널 양방향 시각비교 연구

UTC (Coordinated Universal Time) has been made by the comparison results and the statistical analysis of primary clocks maintained by national standard institutes. Some kinds of technique have been used for international time transfer; since 1980s the study on methods and development of time transfer has conducted with activation of GPS application. And the more accurate and easier method made it use the official time transfer method for the generation of UTC. But recently TWSTFT (Two-Way Satellite Time and Frequency Transfers) as well as GPS time transfer are increasing in number because the TWSTFT is able to improve the accuracy and precision of time comparison owing to the elimination of the ionospheric and tropospheric delay errors thanks to the reciprocal propagation path. In this paper, we introduce the TWSTFT results by a multi-channel modem comparing with GPS P3-code.

The Future of the UTC Time Scale

ABSTRACT: The international atomic time scale used by broadcast services throughout the world is Coordinated Universal Time (UTC). UTC, defined by the International Telecommunication Union (ITU-R), is maintained by the International Bureau of Weights and Measures (BIPM) in cooperation with the International Earth reference and Rotation Service (IERS). Measurements from timing centers around the world are used to determine UTC. The IERS monitors Earth rotation so UTC can be adjusted to within 0.9 seconds of Earth rotation time (UT1). The adjustments, known as leap-seconds, were implemented in 1972 to permit UT1 to be recovered from UTC for celestial navigation. The frequency of leap seconds is dependent on the dynamics of the decelerating Earth. Current telecommunications systems do not introduce leap seconds in timing their data streams. Consequently, deliberations are ongoing within the ITU-R on the issue of a continuous time scale without leap seconds. The questions and issues will be discussed.

THE PHYSICAL BASIS OF THE LEAP SECOND

International Atomic Time (TAI) is the internationally recognized timescale based on the second of the Systeme International d'Unites produced by the Bureau International des Poids et Mesures using data from timing laboratories around the world. TAI is an atomic timescale without steps. Coordinated Universal Time, the basis of civil time, is derived from TAI but is currently defined such that it is maintained within 0.9 s of Universal Time (UT1), the measure of time defined by the Earth's rotation angle, through the insertion of 1 s increments called leap seconds. The difference between UT1 and TAI that motivates the use of leap seconds is related to the tidal deceleration of the Earth's rotation. However, a recent paper by Deines and Williams claims that the divergence is caused by a relativistic time dilation effect. The purpose of this paper is to explain the physical basis of the leap second and to point out that leap seconds are unrelated to relativity.

Astronomical azimuth determination by the hour angle of Polaris using ordinary total stations

The determination of the astronomical azimuth of a line is not a difficult task for surveyors any more. The aim of this paper is to analyze the theoretical details and errors in order to propose the use of ordinary total stations, for an easy, efficient and accurate determination of the astronomical azimuth of a line by the hour angle method via Polaris sightings. As many modern total stations have a built – in quartz clock they can register automatically the UTC time as well as the angle measurements (horizontal and zenith) of each observation. The total fieldwork time needed is about 10 minutes and the accuracy that may be achieved is about ± 2". This procedure will be proven to be easier than the determination of the geodetic azimuth of the same line. The calculation is independent and the result is free of the errors that the coordinates of a survey mark may contain, because they are not used. However good positional data is required from other sources. Astronomical azimuths are an alternative solution for the surveyors in order to check or orient their field surveys and arbitrary networks independent of the GPS system.

Time and Frequency Activities at the U.S. Naval Observatory

The US Naval Observatory (USNO) has provided timing for the navy since 1830 and, in cooperation with other institutions, has also provided timing for the United States and the international community. Its Master Clock (MC) is the source of UTC(USNO), the USNO′s realization of Coordinated Universal Time (UTC), which has stayed within 5 nanoseconds RMS of UTC since 1999. The data used to generate UTC(USNO) are based upon 73 cesium and 21 hydrogen maser frequency standards in three buildings at two sites. The USNO disseminates time via voice, telephone modem, LORAN, Network Time Protocol (NTP), GPS, and two‐way satellite time transfer (TWSTT). This paper describes some of the changes being made to meet the future needs for precision, accuracy, and robustness.

Calculation of Elapsed Decimal Time for Tracing Studies

Calculation of time of travel from tracing studies in hydrologic systems is critical to establishing pollutant arrival times from points of inflow to points outflow, calculating subsurface flow velocities, and determining other important transport parameters such as longitudinal dispersion. In addition, breakthrough curve modeling demands accurate time of travel calculations if model results are to have any realistic meaning. However, accurate time of travel calculations are very difficult for long tracer tests in which sampling schedules are not consistent, or when there are major disruptions such as may occur when adverse weather conditions cause automatic sampling equipment to fail. Long and inconsistent sampling times may be accurately converted to decimal times of travel by converting the conventionally recorded Coordinated Universal Time for sampling date and time event to a baseline time standard. By converting to a baseline time standard, all recorded dates and times are linked to the established baseline standard so that each succeeding sampling date and time are correctly determined relative to the previous sampling date and time and to the injection date and time.

Design of The Wearable Gadgets for Life-Log Services based on UTC

A life-log means a recording the interesting events or the daily life of an individual as the digital method. The types of information for life log are as follows: a photograph, voice, the activity, physiological signals, time information, and location of user. In this paper, the design of wearable gadgets for life-log service based on UTC is presented. We designed of two kinds of wearable gadgets. The firstly is wearable gadget for low rate data (e.g., location), the second is wearable gadget for high rate data (e.g., video). The gadgets acquire the UTC (universal time coordinated) time information by using GPS from a satellite. The acquired time (UTC) are included in acquired life log data from the different systems such as an image, an audio, a bio-signal, environmental information, etc. The measured life-log signals and environment signals in a daily life can be merged with the synchronized time and position information. This information can be realized the obtained time of life log data later. Therefore, it makes more and more useful information can be obtained. This can also provide much usability to retrieve data of life log.

Spontaneous epidural hematoma recurred three times

Spontaneous spinal epidural hematoma (SSEH) is a rare space-occupying disease. The pathogenesis of SSEH is unclear, but anticoagulant therapy, arteriovenous malformation, coagulopathy, tumors and infection are risk factors. Ventral SSEH is even more rare, as the ventral sac is fixed firmly to the posterior longitudinal ligament. The authors report a very rare case, a 16-year-old previously healthy female who had repeated relapse of cervico-thoracic SSEH. This occurred three times in the ventral epidural space with subsequent syringomyelia, without structural abnormality and coagulopathy. The patient underwent conservative care twice, and two operations. The diagnosis was made by magnetic resonance imaging. In rapidly progressing SSEH, the clinician should make the diagnosis as early as possible to enable spinal decompression surgery.

Route to Lambda in conformally coupled phantom cosmology

In this Letter we investigate acceleration in the flat cosmological model with a conformally coupled phantom field and we show that acceleration is its generic feature. We reduce the dynamics of the model to a 3-dimensional dynamical system and analyze it on a invariant 2-dimensional submanifold. Then the concordance FRW model with the cosmological constant Λ is a global attractor situated on a 2-dimensional invariant space. We also study the behaviour near this attractor, which can be approximated by the dynamics of the linearized part of the system. We demonstrate that trajectories of the conformally coupled phantom scalar field with a simple quadratic potential crosses the cosmological constant barrier infinitely many times in the phase space. The universal behaviour of the scalar field and its potential is also calculated. We conclude that the phantom scalar field conformally coupled to gravity gives a natural dynamical mechanism of concentration of the equation of state coefficient around the magical value w eff = − 1 . We demonstrate route to Lambda through the infinite times crossing the w eff = − 1 phantom divide.

Absolute frequency measurement and high resolution spectroscopy of 115In + 5s 21S 0–5s5p 3P 0 narrowline transition

We measure the frequency of the 5s 2 1S 0–5s5p 3P 0 narrowline clock transition at 236.5 nm, for a single, trapped and laser cooled 115In + ion. In the experiment, an ultra-narrow linewidth laser (<1.34 Hz at 3 s integration time) is used to interrogate the clock transition for high resolution spectroscopy. A linewidth of 43 Hz of the clock transition is observed. The uncertainty of the line centroid is 18 Hz, leading to a fractional uncertainty of 1.4 × 10 - 14 . The frequency is measured by using an optical frequency comb referenced to a cesium clock. The transition frequency is found to be 1, 267, 402, 452, 901.265 (256) kHz, averaged over 13 days of separate measurement. The accuracy of 2.35 × 10 - 13 is due to the reference cesium clock calibrated against UTC time. We discuss ways for further improvements.

On the Identification and Documentation of Timing Errors: An Example at the KBS Station, Spitsbergen

The availability of high-quality digital seismic data has never been better than it is today. Through consortia such as the Incorporated Research Institutions for Seismology (IRIS) and Observatories and Research Facilities for European Seismology (ORFEUS), waveform data from stations of many worldwide networks are available via the Internet to the international community of seismologists. When a user examines a segment of data, it is assumed that the time displayed is the exact time in Coordinated Universal Time (UTC) at which the motion was recorded. In general, when retrieving data segments from a waveform repository, there is no independent confirmation of the validity of the time stamp. In this paper, I discuss a case where a user discovered an erroneous time stamp on data from a single-site station. A fortuitous source of repeating seismic signals, together with data from another nearby station, facilitated measurement of the timing anomaly during the period in question. Erroneous timing on seismograms might be more widespread than assumed; the identification and documentation of such cases requires more attention. The IRIS/GEOFON/AWI seismic station at King's Bay Station (KBS) is situated near Ny Alesund, King's Bay, on the Arctic island of Spitsbergen (figure 1). The location is important in the context of nuclear-explosion monitoring due to the relative proximity of the Russian island of Novaya Zemlya, the site of numerous Soviet-era nuclear tests, the last known event being on 24 October 1990. Also on Spitsbergen, a highly sensitive small-aperture seismic array, SPITS, became operational in 1994 and is now a designated Auxiliary Seismic Array (AS72) of the International Monitoring System (IMS) of the Comprehensive Nuclear Test-Ban-Treaty Organization (CTBTO). However, the KBS station is still of great importance given both the high quality of the continuous seismic data and the availability of the historical data recorded at that site. …

Analysis of mesoscale convective systems over Tibetan Plateau in summer

In this paper, Geostationary Meteorological Satellite (GMS) infrared black-body temperature (Tbb) data from June to August 1998 are used to automatically track the activity of Mesoscale Convective System (MCS) over the Tibetan Plateau in China. Consequently, the features of MCS, such as area, intensity, life cycle, activity region and shape, are obtained. High Resolution Limited Area Analysis and Forecasting System (HLAFS) values provided by China National Meteorological Center are used to study the relationships between the MCS trajectories and their environmental physical field values, based on the distribution and trajectories of MCSs over the Tibetan Plateau. Favorable environmental physical field charts of influencing MCS movement out of the Tibetan Pleteau in different UTC (Universal Time Coordinate) are developed by using spatial data mining techniques at levels of 400hPa and 500hPa, respectively.