scholarly journals Review of the achievements of project MERIT for the intercomparison of techniques for monitoring the rotation of the Earth

1988 ◽  
Vol 128 ◽  
pp. 227-232
Author(s):  
G. A. Wilkins
Keyword(s):  
Earth Rotation ◽  
Working Group ◽  
New Techniques ◽  
New Methods ◽  
The Earth ◽  
Terrestrial Reference System ◽  
Rotation Of The Earth ◽  
Analyse Data ◽  
Set Up ◽  
International Services

It is generally recognised that the Working Group on the Rotation of the Earth that was set up after IAU Symposium No. 82 has successfully achieved its principal objectives, namely: “to make recommendations on … future international services on earth-rotation” and “to obtain and analyse data on earth-rotation by both current and new methods …”. In particular, by organising Project MERIT, it has stimulated the development and use of new techniques and it has brought together in fruitful collaboration scientists from many countries and disciplines. Other subsidiary objectives have also been achieved and the project has been extended through cooperation with the COTES Working Group on the terrestrial reference system. The possible reasons for this success are also reviewed in the expectation that the conclusions will be relevant to other future projects.

scholarly journals Joint Summary Report of the IAU/IUGG Working Groups on the Rotation of the Earth and the Terrestrial Reference System

1986 ◽  
Vol 7 ◽  
pp. 771-788
Author(s):  
G. A. Wilkins ◽  
I. I. Mueller
Keyword(s):  
Earth Rotation ◽  
Working Group ◽  
Reference System ◽  
Lunar Laser Ranging ◽  
Long Baseline ◽  
The Earth ◽  
Earth Rotation Parameters ◽  
Working Groups ◽  
Terrestrial Reference System ◽  
Rotation Of The Earth

AbstractThe Working Group on the Rotation of the Earth was established in 1978 and developed a programme of international collaboration to Monitor Earth-Rotation and Intercompare the Techniques of observation and analysis (MERIT). The MERIT Short Campaign was held in 1980 to test and develop the organisational arrangements required during the MERIT Main Campaign in 1983-4. The Working Group on the Terrestrial Reference System was established in 1980 to prepare a proposal for the establishment and maintenance of a new Conventional Terrestrial Reference System (COTES) that would be based on the new techniques of space geodesy. The Working Groups collaborated closely and organised two intensive campaigns in 1984 and 1985 that were aimed primarily at determining the relationships between the reference systems of the six different techniques that were used to determine earth-rotation parameters. Observational data were obtained from 35 countries; analyses and intercomparisons of the results were carried out in 7 countries. The Working Groups reviewed the results at the Third MERIT Workshop and recommended that a new International Earth Rotation Service be set up in 1988 and that it be based on the use of very-long-baseline radio interferometry and both satellite and lunar laser ranging.

The Terrestrial Coordinate System and International Earth-rotation Services

1985 ◽  
Vol 38 (02) ◽  
pp. 216-217
Author(s):  
G. A. Wilkins
Keyword(s):  
Coordinate System ◽  
Earth Rotation ◽  
Reference System ◽  
New Techniques ◽  
Crustal Movements ◽  
Earth Observations ◽  
The Earth ◽  
External Reference ◽  
External Objects ◽  
Rotation Of The Earth

New techniques of measurement make it possible in 1984 to determine positions on the surface of the Earth to a much higher precision than was possible in 1884. If we look beyond the requirements of navigation we can see useful applications of global geodetic positioning to centimetric accuracy for such purposes as the control of mapping and the study of crustal movements. These new techniques depend upon observations of external objects, such as satellites or quasars rather than stars, and they require that the positions of these objects and the orientation of the surface of the Earth are both known with respect to an appropriate external reference system that is ‘fixed’ in space. We need networks of observing stations and analysis centres that monitor the motions of the external objects and the rotation of the Earth. Observations of stars by a transit circle are no longer adequate for this purpose.

scholarly journals The Calculation of the Nutations

1974 ◽  
Vol 3 ◽  
pp. 221-222
Author(s):  
R. O. Vicente
Keyword(s):  
Working Group ◽  
Polar Motion ◽  
Financial Difficulties ◽  
The Earth ◽  
International Astronomical ◽  
Earth Models ◽  
International Polar ◽  
Rotation Of The Earth ◽  
Set Up ◽  
Original Observation

It is well known that the knowledge of precession and nutation is essential for the computation of astronomical coordinates and the comparison of values obtained at different dates. It is therefore important to compute the nutations from the best available observations.Unfortunately, there are not many long series of reliable observations that can be used for the calculation of the several nutations. Nowadays, we need more accurate values and, therefore, it is fundamental to have observations reduced in an homogeneous way. For this purpose, Commission 19 (Rotation of the Earth) set up a ‘Working Group on Pole Coordinates’, during the last IAU meeting in 1970 (Vicente, 1972), with the objective of reducing the 70 years of variation of latitude observations done by the International Latitude Service (called the International Polar Motion Service at the present time) that constitute a remarkable set of astronomical data. It is expected to obtain more reliable values for the coordinates of the pole and be able to calculate the nutations.The Working Group on Pole Coordinates is transferring to punched cards all the observations registered in the original observation books and that involves nearly 2 million cards. This work has been hampered by financial difficulties, but it should be supported by the international astronomical community in order to obtain the best results from so many years of observations, done by international cooperation.The theoretical researches done in the last decades have shown that the values of the nutations depend on the structure of the Earth (Jeffreys and Vicente, 1957). Lately, the researches done in seismology have resulted in a better knowledge about the structure of the Earth, leading to the setting up of many Earth models due to the availability of computers. This fact has led to the situation where one cannot propose better theoretical values for the nutations because they depend on the model adopted for the structure of the Earth.

scholarly journals Seasonal variations and north–south asymmetries in polar wind outflow due to solar illumination

2016 ◽  
Vol 34 (11) ◽  
pp. 961-974 ◽  
Author(s):  
Lukas Maes ◽  
Romain Maggiolo ◽  
Johan De Keyser
Keyword(s):  
Seasonal Variations ◽  
Solar Zenith Angle ◽  
The Sun ◽  
Polar Ionosphere ◽  
Polar Cap ◽  
Polar Wind ◽  
Simple Set ◽  
The Earth ◽  
Rotation Of The Earth ◽  
Set Up

Abstract. The cold ions (energy less than several tens of electronvolts) flowing out from the polar ionosphere, called the polar wind, are an important source of plasma for the magnetosphere. The main source of energy driving the polar wind is solar illumination, which therefore has a large influence on the outflow. Observations have shown that solar illumination creates roughly two distinct regimes where the outflow from a sunlit ionosphere is higher than that from a dark one. The transition between both regimes is at a solar zenith angle larger than 90°. The rotation of the Earth and its orbit around the Sun causes the magnetic polar cap to move into and out of the sunlight. In this paper we use a simple set-up to study qualitatively the effects of these variations in solar illumination of the polar cap on the ion flux from the whole polar cap. We find that this flux exhibits diurnal and seasonal variations even when combining the flux from both hemispheres. In addition there are asymmetries between the outflows from the Northern Hemisphere and the Southern Hemisphere.

scholarly journals Commission 19: Rotation of the Earth

1985 ◽  
Vol 19 (1) ◽  
pp. 193-205 ◽  
Author(s):  
Ya. S. Yatskiv ◽  
W. J. Klepczynski ◽  
F. Barlier ◽  
H. Enslin ◽  
C. Kakuta ◽  
...  
Keyword(s):  
Time Frame ◽  
Laser Ranging ◽  
Earth’S Rotation ◽  
The Moon ◽  
Earth's Rotation ◽  
The Earth ◽  
Long Time ◽  
Terrestrial Reference System ◽  
Rotation Of The Earth

During the period, work on the problem of the Earth’s rotation has continued to expand and increase its scope. The total number of institutions engaged in the determination of the Earth’s rotation parameters (ERP) by different techniques has been increased significantly. The rotation of the Earth is currently measured by classical astrometry, Doppler and laser satellite tracking, laser ranging of the Moon, and radio interferometry. Several long time series of the ERP are available from most of these techniques, in particular, those made during the Main Campaign of the MERIT project. The various series have been intercompared and their stability, in the time frame of years to days, has been estimated for the purposes of establishing a new conventional terrestrial reference system (COTES). On the other hand, the difficulties of maintaining a regular operation for laser ranging to the Moon (LLR) have been recognized. It resulted in the proposal to organize an one-month campaign of observations in 1985 in order to complement the COTES collocation program and to allow additional intercomparisons with other techniques.

scholarly journals Basic Problems in the Kinematics of the Rotation of the Earth

1979 ◽  
Vol 82 ◽  
pp. 7-18 ◽  
Author(s):  
Bernard Guinot
Keyword(s):  
Earth Rotation ◽  
Rotation Axis ◽  
Earth’S Rotation ◽  
International Astronomical Union ◽  
Earth's Rotation ◽  
The Earth ◽  
International Astronomical ◽  
Rotation Of The Earth

With the advent of more precise methods for measuring Earth rotation, a number of corrections to the apparent directions in space, to the terrestrial references, and to the rotation axis motion have to be carefully applied. It is the duty of the international Astronomical Union to give recommended or conventional expressions of these corrections in order to avoid inextricable difficulties in discussing the evaluated results. However, this task is not sufficient. The concepts used in the description of the Earth's rotation are somewhat obscured by traditions. They should be purified by removing notions which are not directly relevant.

scholarly journals The Origin of Celestial Coordinates

1990 ◽  
Vol 141 ◽  
pp. 51-59
Author(s):  
C. A. Murray
Keyword(s):  
Earth Rotation ◽  
Zero Point ◽  
Rate Of Change ◽  
Reference Systems ◽  
The Earth ◽  
Private Correspondence ◽  
Rotation Of The Earth ◽  
Right Ascension

In 1978, Guinot proposed that, for studies of Earth rotation, the zero point of the apparent “right ascension” coordinate on the true equator should be so chosen that the rate of change of its hour angle is exactly proportional to the inertial rate of rotation of the Earth. It has been subsequently suggested that this concept of the “non-rotating origin” supersede the equinox quite generally as the origin of celestial coordinates. Since this proposal was first put forward, there has been much discussion, and some criticism, from Aoki and his colleagues, both published and in private correspondence. Some of the arguments for and against Guinot's proposal are discussed, as a contribution to the wider debate on reference systems now being carried out under the auspices of the IAU.

scholarly journals COMMISSION 19: ROTATION OF THE EARTH

2008 ◽  
Vol 4 (T27A) ◽  
pp. 37-49
Author(s):  
Aleksander Brzezinski ◽  
Chopo Ma ◽  
Véronique Dehant ◽  
Pascale Defraigne ◽  
Jean O. Dickey ◽  
...  
Keyword(s):  
Earth Rotation ◽  
Reference Frames ◽  
International Association ◽  
Vice President ◽  
Past President ◽  
Scientific Investigations ◽  
The Earth ◽  
International Vlbi Service ◽  
Commission President ◽  
Rotation Of The Earth

The Commission supports and coordinates scientific investigations in the Earth rotation and related reference frames. Several changes had been introduced to the structure of Commission 19 since the IAU XXVI General Assembly in Prague, 2006. The Organizing Committee of Commission 19 has been substantially reduced. It consists now of six ex-officio members, the Commission president, vice-president, past president and representatives from the International Association of Geodesy (IAG), International Earth Rotation and Reference Systems Service (IERS), International VLBI Service for Geodesy and Astrometry (IVS), and five members at-large who are nominated by the OC, selected by the Commission members and elected by the IAU GA for a maximum of two terms. The modified terms of reference of Commission 19, the list of members and other details can be found at the Commission website <iau-comm19.cbk.waw.pl/>.

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