Dennis McCarthy - Academia.edu (original) (raw)

Papers by Dennis McCarthy

Geophysical Journal International, 1993

Observations of the length of day, corrected for the effects of variations in the angular momentu... more Observations of the length of day, corrected for the effects of variations in the angular momentum due to changes in wind velocity and atmospheric pressure, ocean-tide heights and currents, and solid-Earth zonal tides, were analysed. The (1992) IERS Standards model for the effects of zonal tides on the Earth's rotation, which includes ocean-tidal effects, adequately accounts for the observations of the high-frequency (periods between one and 30 days) variations in the length of day at the present level of accuracy. A currently unexplained semi-annual variation in the length of day remains, but this may be due to the unmodelled effects of stratospheric winds. The power spectrum of the remaining variations with periods less than 20 days is essentially that of a white-noise process. The amplitudes of the remaining unexplained variations in length of day are less than 30 microseconds.

Time - From Earth Rotation to Atomic Physics

Time - From Earth Rotation to Atomic Physics

Highlights of Astronomy, 1998

Systematic errors caused by the use of inconsistent models and constants currently limit the accu... more Systematic errors caused by the use of inconsistent models and constants currently limit the accuracy of the most precise astro-geodetic observations. It is important, therefore, to provide conventional estimates of astronomical constants for general use in astronomy and geodesy. Establishment of such a set raises issues involving the accuracy of the constants, their internal consistency, and the reference system in which they are expressed. Future sets of constants will be updated at regular intervals to provide the most accurate values at that instant. Careful consideration must be given to their internal consistency. It is likely that they will be provided only in electronic format with references to their determination and to procedures for their use.

Historical & Cultural Astronomy, 2020

Astrophysics and Space Science Proceedings, 2017

Time and timekeeping are subjects of long-standing discussions in the fields of science and philo... more Time and timekeeping are subjects of long-standing discussions in the fields of science and philosophy. Timekeeping requires some regularly repeatable natural phenomenon, e.g., a year or a day along with established conventions regarding (1) the interval between repetitions, (2) when the series of repetitions is recognized to begin, (3) the names for successive repetitions and their subdivisions, and (4) the means by which this information can be distributed. Beginning with early man, repetitive astronomical phenomena provided obvious answers to these concerns, the regular appearance of the Sun and Moon being the most obvious. Evolving civilization made it necessary to develop increasingly sophisticated concepts regarding time as well as increasingly sophisticated measurements of the passage of time. Particularly notable steps in the evolution of concepts of time involve the thoughts of Aristotle, Newton, and our understanding of the principles of special and general relativity. Particularly notable events in timekeeping range from sundials, water clocks, mechanical clocks, to atomic clocks, all of these devices being related to increasingly sophisticated astronomical observations.

Time - From Earth Rotation to Atomic Physics

Contributions of Space Geodesy to Geodynamics: Earth Dynamics, 1993

We present a first description of the changes in the current procedures that will have to be perf... more We present a first description of the changes in the current procedures that will have to be performed in order to take into account the adoption of the ICRS as the new reference system and new nutation-precession series. A number of choices will have to be made: they are presented in this paper.

International Astronomical Union Colloquium, 1991

Modern observations of celestial pole offsets indicate that small but significant corrections to ... more Modern observations of celestial pole offsets indicate that small but significant corrections to the current IAU theories of nutation and precession can be detected. These corrections are of the order of a few milliseconds of arc. To meet the needs of those who require millisecond of arc accuracy in reference frame applications, the International Earth Rotation Service (IERS) publishes in weekly and monthly bulletins the most recent observations, along with predictions of these corrections. These appear to meet the needs of users. In view of the fact that the geophysical community has not adopted a model which describes the nutation and precession theory and that the current procedure of the IERS meets the need of high-accuracy users, there does not appear to be a need to identify a new IAU nutation theory at this time.

International Astronomical Union Colloquium, 2000

The current definition of Coordinated Universal Time (UTC) is related to the unpredictable, varia... more The current definition of Coordinated Universal Time (UTC) is related to the unpredictable, variable rotation rate of the Earth. This is accomplished by irregular insertions of leap seconds, creating unpredictable discontinuities in UTC. With the increasing importance of a continuous, uniform time scale for users, it is appropriate to re-examine the current definition of this time scale. There are several possibilities to address this problem, and it is appropriate that the International Astronomical Union establish a working group to investigate the continuing need for leap seconds and possible changes in the definition of UTC.

Symposium - International Astronomical Union, 1988

Predictions of Earth orientation parameters are affected by the accuracy of the input data, the q... more Predictions of Earth orientation parameters are affected by the accuracy of the input data, the quality of the statistical models, and the delay between the last observed data and the date of the first prediction. The accuracy of the prediction of polar motion is adequate to meet most user needs, but the prediction of UT1-UTC is more difficult. Extended forecasts of polar motion and the rotational time can also be made with useful accuracies.

Symposium - International Astronomical Union, 1988

Predictions of Earth orientation parameters are affected by the accuracy of the input data, the q... more Predictions of Earth orientation parameters are affected by the accuracy of the input data, the quality of the statistical models, and the delay between the last observed data and the date of the first prediction. The accuracy of the prediction of polar motion is adequate to meet most user needs, but the prediction of UT1-UTC is more difficult. Extended forecasts of polar motion and the rotational time can also be made with useful accuracies.

Highlights of Astronomy, 2005

The IAU Joint Discussion 16 (JD16) was held in conjunction with the XXVth General Assembly in Jul... more The IAU Joint Discussion 16 (JD16) was held in conjunction with the XXVth General Assembly in July, 2003. Papers related to the maintenance of the International Celestial Reference System were presented in the one-day session, and these were followed by discussion that pointed out the need for standard nomenclature. This issue was addressed by the formation of a Division 1 Working Group on the subject. JD16 also pointed out the requirement for a dynamical expression for precession which was addressed by the creation of a Division 1 Working Group on Precession and the Ecliptic. It also showed that although plans are being implemented to provide reference frames for the future, there is a need for improved coordination of astrometric observations. Finally it should be noted that the discussion pointed out the concern for the future organization of IAU Division 1.

Highlights of Astronomy, 2002

Past endeavors in the field of Earth orientation have provided both service to astronomical users... more Past endeavors in the field of Earth orientation have provided both service to astronomical users of the data and insight into the physical processes of the planet Earth. Since the study of Earth orientation has required a wide geographic distribution of astronomical observing sites, it has been an area of research that has depended heavily on international cooperation over long intervals of time. Recently, IAU Colloquium 178 pointed out that the need exists to find and collect observations that may have been made before the establishment of the current operational services. Reanalysis of such data could be important in our understanding of the physical processes affecting the Earth. All of these observations need to be analyzed in one system consistent with current definitions and conventions. The history of available observations is reviewed along with the contributions that have been made possible using these data. Possible sources for additional data are suggested.

Highlights of Astronomy, 2002

Analyses of residuals between VLBI observations and combinations of nutation series show that the... more Analyses of residuals between VLBI observations and combinations of nutation series show that the MHB 2000 nonrigid-Earth nutation model applied to the REN 2000 rigid-Earth model results in the best fit, and that amplitudes of any possible periodic terms remaining in the observed corrections to the MHB2000 theory could be expected to be less than 0.1 mas.

Time scales evolve to meet user needs consistent with our understanding of the underlying physics... more Time scales evolve to meet user needs consistent with our understanding of the underlying physics. The measurement of time strives to take advantage of the most accurate measurement techniques available. As a result of improvements in both science and in measurement technology, the past fifty years has witnessed a growing number of time scales as well as the virtual extinction of some. The most significant development in timing has been the switch to frequencies of atomic transitions and away from the Earth's rotation angle as the fundamental physical phenomenon providing precise time.

Iau Joint Discussion, 2000

Matrix: A= Rye, B= Mix wheat/oat (1:1) 1) robust relative standard deviation (interlaboratory RSD... more Matrix: A= Rye, B= Mix wheat/oat (1:1) 1) robust relative standard deviation (interlaboratory RSD based on participants' results). 2) calculated using a fit-for-purpose target RSD for proficiency of 25%. False negatives were counted here as unsatisfactory z-score. 3) the number and percentage here means: analyte determined, method with a sufficiently low LOQ to allow quantification, and obtaining a satisfactory z-score. Material A Ergosine A: 81.9 µg/kg u: 2.75 µg/kg σp: 20.5 µg/kg (25%) robust σ: 12.5 µg/kg (15%) Ergosinine A: 46.0 µg/kg u: 2.58 µg/kg σp: 11.5 µg/kg (25%) robust σ: 11.5 µg/kg (25%) Ergotamine A: 126 µg/kg u: 5.66 µg/kg σp: 31.5 µg/kg (25%) robust σ: 25.2 µg/kg (20%) Ergotaminine A: 65.3 µg/kg u: 3.20 µg/kg σp: 16.3 µg/kg (25%) robust σ: 14.3 µg/kg (22%) Total sum A: 701 µg/kg u: 24.0 µg/kg σp: 175 µg/kg (25%) robust σ: 110 µg/kg (16%)

Geophysical Journal International, 1993

Observations of the length of day, corrected for the effects of variations in the angular momentu... more Observations of the length of day, corrected for the effects of variations in the angular momentum due to changes in wind velocity and atmospheric pressure, ocean-tide heights and currents, and solid-Earth zonal tides, were analysed. The (1992) IERS Standards model for the effects of zonal tides on the Earth's rotation, which includes ocean-tidal effects, adequately accounts for the observations of the high-frequency (periods between one and 30 days) variations in the length of day at the present level of accuracy. A currently unexplained semi-annual variation in the length of day remains, but this may be due to the unmodelled effects of stratospheric winds. The power spectrum of the remaining variations with periods less than 20 days is essentially that of a white-noise process. The amplitudes of the remaining unexplained variations in length of day are less than 30 microseconds.

Time - From Earth Rotation to Atomic Physics

Time - From Earth Rotation to Atomic Physics

Highlights of Astronomy, 1998

Systematic errors caused by the use of inconsistent models and constants currently limit the accu... more Systematic errors caused by the use of inconsistent models and constants currently limit the accuracy of the most precise astro-geodetic observations. It is important, therefore, to provide conventional estimates of astronomical constants for general use in astronomy and geodesy. Establishment of such a set raises issues involving the accuracy of the constants, their internal consistency, and the reference system in which they are expressed. Future sets of constants will be updated at regular intervals to provide the most accurate values at that instant. Careful consideration must be given to their internal consistency. It is likely that they will be provided only in electronic format with references to their determination and to procedures for their use.

Historical & Cultural Astronomy, 2020

Astrophysics and Space Science Proceedings, 2017

Time and timekeeping are subjects of long-standing discussions in the fields of science and philo... more Time and timekeeping are subjects of long-standing discussions in the fields of science and philosophy. Timekeeping requires some regularly repeatable natural phenomenon, e.g., a year or a day along with established conventions regarding (1) the interval between repetitions, (2) when the series of repetitions is recognized to begin, (3) the names for successive repetitions and their subdivisions, and (4) the means by which this information can be distributed. Beginning with early man, repetitive astronomical phenomena provided obvious answers to these concerns, the regular appearance of the Sun and Moon being the most obvious. Evolving civilization made it necessary to develop increasingly sophisticated concepts regarding time as well as increasingly sophisticated measurements of the passage of time. Particularly notable steps in the evolution of concepts of time involve the thoughts of Aristotle, Newton, and our understanding of the principles of special and general relativity. Particularly notable events in timekeeping range from sundials, water clocks, mechanical clocks, to atomic clocks, all of these devices being related to increasingly sophisticated astronomical observations.

Time - From Earth Rotation to Atomic Physics

Contributions of Space Geodesy to Geodynamics: Earth Dynamics, 1993

We present a first description of the changes in the current procedures that will have to be perf... more We present a first description of the changes in the current procedures that will have to be performed in order to take into account the adoption of the ICRS as the new reference system and new nutation-precession series. A number of choices will have to be made: they are presented in this paper.

International Astronomical Union Colloquium, 1991

Modern observations of celestial pole offsets indicate that small but significant corrections to ... more Modern observations of celestial pole offsets indicate that small but significant corrections to the current IAU theories of nutation and precession can be detected. These corrections are of the order of a few milliseconds of arc. To meet the needs of those who require millisecond of arc accuracy in reference frame applications, the International Earth Rotation Service (IERS) publishes in weekly and monthly bulletins the most recent observations, along with predictions of these corrections. These appear to meet the needs of users. In view of the fact that the geophysical community has not adopted a model which describes the nutation and precession theory and that the current procedure of the IERS meets the need of high-accuracy users, there does not appear to be a need to identify a new IAU nutation theory at this time.

International Astronomical Union Colloquium, 2000

The current definition of Coordinated Universal Time (UTC) is related to the unpredictable, varia... more The current definition of Coordinated Universal Time (UTC) is related to the unpredictable, variable rotation rate of the Earth. This is accomplished by irregular insertions of leap seconds, creating unpredictable discontinuities in UTC. With the increasing importance of a continuous, uniform time scale for users, it is appropriate to re-examine the current definition of this time scale. There are several possibilities to address this problem, and it is appropriate that the International Astronomical Union establish a working group to investigate the continuing need for leap seconds and possible changes in the definition of UTC.

Symposium - International Astronomical Union, 1988

Predictions of Earth orientation parameters are affected by the accuracy of the input data, the q... more Predictions of Earth orientation parameters are affected by the accuracy of the input data, the quality of the statistical models, and the delay between the last observed data and the date of the first prediction. The accuracy of the prediction of polar motion is adequate to meet most user needs, but the prediction of UT1-UTC is more difficult. Extended forecasts of polar motion and the rotational time can also be made with useful accuracies.

Symposium - International Astronomical Union, 1988

Predictions of Earth orientation parameters are affected by the accuracy of the input data, the q... more Predictions of Earth orientation parameters are affected by the accuracy of the input data, the quality of the statistical models, and the delay between the last observed data and the date of the first prediction. The accuracy of the prediction of polar motion is adequate to meet most user needs, but the prediction of UT1-UTC is more difficult. Extended forecasts of polar motion and the rotational time can also be made with useful accuracies.

Highlights of Astronomy, 2005

The IAU Joint Discussion 16 (JD16) was held in conjunction with the XXVth General Assembly in Jul... more The IAU Joint Discussion 16 (JD16) was held in conjunction with the XXVth General Assembly in July, 2003. Papers related to the maintenance of the International Celestial Reference System were presented in the one-day session, and these were followed by discussion that pointed out the need for standard nomenclature. This issue was addressed by the formation of a Division 1 Working Group on the subject. JD16 also pointed out the requirement for a dynamical expression for precession which was addressed by the creation of a Division 1 Working Group on Precession and the Ecliptic. It also showed that although plans are being implemented to provide reference frames for the future, there is a need for improved coordination of astrometric observations. Finally it should be noted that the discussion pointed out the concern for the future organization of IAU Division 1.

Highlights of Astronomy, 2002

Past endeavors in the field of Earth orientation have provided both service to astronomical users... more Past endeavors in the field of Earth orientation have provided both service to astronomical users of the data and insight into the physical processes of the planet Earth. Since the study of Earth orientation has required a wide geographic distribution of astronomical observing sites, it has been an area of research that has depended heavily on international cooperation over long intervals of time. Recently, IAU Colloquium 178 pointed out that the need exists to find and collect observations that may have been made before the establishment of the current operational services. Reanalysis of such data could be important in our understanding of the physical processes affecting the Earth. All of these observations need to be analyzed in one system consistent with current definitions and conventions. The history of available observations is reviewed along with the contributions that have been made possible using these data. Possible sources for additional data are suggested.

Highlights of Astronomy, 2002

Analyses of residuals between VLBI observations and combinations of nutation series show that the... more Analyses of residuals between VLBI observations and combinations of nutation series show that the MHB 2000 nonrigid-Earth nutation model applied to the REN 2000 rigid-Earth model results in the best fit, and that amplitudes of any possible periodic terms remaining in the observed corrections to the MHB2000 theory could be expected to be less than 0.1 mas.

Time scales evolve to meet user needs consistent with our understanding of the underlying physics... more Time scales evolve to meet user needs consistent with our understanding of the underlying physics. The measurement of time strives to take advantage of the most accurate measurement techniques available. As a result of improvements in both science and in measurement technology, the past fifty years has witnessed a growing number of time scales as well as the virtual extinction of some. The most significant development in timing has been the switch to frequencies of atomic transitions and away from the Earth's rotation angle as the fundamental physical phenomenon providing precise time.

Iau Joint Discussion, 2000

Matrix: A= Rye, B= Mix wheat/oat (1:1) 1) robust relative standard deviation (interlaboratory RSD... more Matrix: A= Rye, B= Mix wheat/oat (1:1) 1) robust relative standard deviation (interlaboratory RSD based on participants' results). 2) calculated using a fit-for-purpose target RSD for proficiency of 25%. False negatives were counted here as unsatisfactory z-score. 3) the number and percentage here means: analyte determined, method with a sufficiently low LOQ to allow quantification, and obtaining a satisfactory z-score. Material A Ergosine A: 81.9 µg/kg u: 2.75 µg/kg σp: 20.5 µg/kg (25%) robust σ: 12.5 µg/kg (15%) Ergosinine A: 46.0 µg/kg u: 2.58 µg/kg σp: 11.5 µg/kg (25%) robust σ: 11.5 µg/kg (25%) Ergotamine A: 126 µg/kg u: 5.66 µg/kg σp: 31.5 µg/kg (25%) robust σ: 25.2 µg/kg (20%) Ergotaminine A: 65.3 µg/kg u: 3.20 µg/kg σp: 16.3 µg/kg (25%) robust σ: 14.3 µg/kg (22%) Total sum A: 701 µg/kg u: 24.0 µg/kg σp: 175 µg/kg (25%) robust σ: 110 µg/kg (16%)