Astronomical Determination Research Articles

A DEPARTMENTAL RESERVE OF GEODETIC ALGORITHMS AND PROGRAMS

The authors describe the organization and operation of a reserve or information bank of computer programs (OFAP) of the Main Administration of Geodesy and Cartography (GUGK). Available software includes programs for adjusting horizontal and vertical survey control nets and triangulation grids, calculating datum points, and processing astronomical determinations. The programs are designed and documented within individual GUGK departments, debugged and cataloged by reserve personnel, and copies delivered to user organizations and to a State Reserve of Algorithms and Programs (GosFAP). Translated from: Geodeziya i kartografiya, 1985, No. 4, pp. 47-50.

The period-luminosity relation of Mira stars

Published photometry in Sgri is used to derive the period-luminosity relation for Mira variables in yellow and in blue light. The observed dispersion about the adopted relation is comparable to that of RR Lyrae-stars around their mean luminosity. This suggests that the Mira star period-luminosity relation has a relatively small dispersion and is, therefore, a powerful tool for astronomical distance determination. The calibration of the Mira period-luminosity relation indicates that Glass and Feast may have overestimated the absorption in the direction of Sgri and NGC 6522.

‘MERIT’ Working Group Plans for a New Earth Rotation Service

During the past 80 years, classical astronomical techniques have been used to determine polar motion (the variation of the direction of the spin axis of the earth with respect to a coordinate system fixed in the earth). The motion, which includes an Eulerian motion of about 0.3″ amplitude with a 430‐day period and a somewhat smaller seasonal variation, is also subject to effects of geophysical processes that cannot be detected reliably because of the 0.01–0.02″ uncertainty (averaged over 5 days) in the astronomical determinations of pole position. The rate of the earth's rotation about its spin axis, measured to about 1‐ms accuracy by astronomical techniques, also has seasonal variations of tens of milliseconds, variations of a few milliseconds over time periods of 2–4 months because of changing wind patterns, and currently undetectable effects as a result of tectonic processes. Higher accuracy and higher frequency determinations of polar motion and the earth–s rotation are required if the data are to be used to learn more about the internal constitution of the earth and earthquake processes.

Contribution of astro - geodetic observations to the improvement of fundamental catalogue

AbstractThe example of astronomical location determination by Zeiss astrolabe shows that the accuracy of many astro-geodetic observations is sufficient for improvement of star positions. An estimation yields a number of 800 visual latitude/longitude determinations with more than 20.000 star transits, annually observed at triangulation points of western Europe alone. It is proposed to forward the residuals of the observed stars to a central agency (e.g. Astronomisches Rechen-Institut Heidelberg) together with parallactic angle and standard deviation. Collecting these data over a period of 5 years the positions of most fundamental stars could be improved with an accuracy better than ± 0.05”.

Effects of tidal dissipation in the oceans on the Moon's orbit and the Earth's Rotation

The dissipation of tidal friction in the oceans and atmosphere has been estimated by calculating the secular perturbations of the moon's orbit by the tides using the available tide models for the principal semidiurnal and diurnal tides. Only the second-degree wavelength components in the ocean tide cause significant secular changes in the lunar orbit. These components of the M2 tide agree within 15% among the different ocean tide models. Other frequencies (O1, N2, S2, P1, and K1) have effects on the lunar motion of about 25% of the M2 tide and on the earth's rotation of about 45% of M2. The computed lunar acceleration of −35 arc sec/(100 yr)2 agrees to better than 15% with nearly all recent astronomical determinations. There has been no significant change in the tidal effect during the last 2000 or 3000 years. The difference between the two estimates of the lunar acceleration is of the same order as their uncertainties. Hence only upper limits can be set on the 1/Q of the solid earth and moon of about 1/50 and on dissipation in the core of about 3×1018 ergs s−1. The total tidal acceleration of the earth is estimated to result in a 3.7-ms/100 yr increase in the length of day. The most recent discussion of the ancient eclipse records indicates an observed increase in the length of day of only 2.5 ms/100 yr. If the nontidal acceleration is attributed to the postglacial response of the earth, the decay time is about 3000 years, which is equivalent to a mean viscosity for the mantle of about 1022 P.

THE MATHEMATICAL BASIS OF RUSSIAN MAPS OF THE 18TH CENTURY

The author shows that in response to Peter the Great's policy of reorganization and modernization there were notable advances in Russian cartography during the 18th century, resulting in more accurate and more complete mapping of the country. She describes the procedures of district surveys, the methods, instruments, and expeditions for the astronomical determination of the coordinates of places, and the types of projections and scales used by general and particular maps and atlases. L'auteur expose comment, à la suite de la politique de réorganisation et de modernisation instaurée par Pierre le Grand, des progrès remarquables ont été accomplis dans la cartographie russe au cours du 18e siècle, ce qui a permis d'obtenir une représentation cartographique du pays beaucoup plus précise et complète. Elle décrit la manière dont sont effectués les levés régionaux, les méthodes et instruments employés et les expéditions entreprises pour la détermination astronomique des coordonnées des lieux, ainsi que les types de projections et d'échelles utilisées pour les cartes et atlas genéraux et particuliers.

Calculating universal time from the results of astronomical determinations

Calculating universal time from the results of astronomical determinations

The Australian Geoid

Abstract This paper describes the determination of the geoid in Australia relative to the Australian Geodetic Datum by the method of astro-geodetic levelling. Gravity observations have been used to fill in detail, but the gravity results everywhere have been adjusted to the astro-geodetic framework. A preliminary geoid has been calculated for Papua and New Guinea and nearby islands using those astronomical determinations which have geodetic co-ordinates on the Australian Geodetic Datum.

On the night errors in astronomical determinations

The discrepancy between precision and accuracy in astronomical determinations is usually explained in two ways: on the one hand by ostensible large refraction anomalies and on the other hand by variable instrumental errors which are systematic over a certain interval of time and which are mainly influenced by temperature.In view of the research of several other persons and the author’s own investigations, the authors are of the opinion that the large night-errors of astronomical determinations are caused by variable, systematic instrumental errors dependent on temperature. The influence of refraction anomalies is estimated to be smaller than 0″.1 for most of the field stations. The possibility of determining the anomalous refraction from the observations by the programme given by Prof. Pavlov and Anderson has also been investigated. The precision of the determination of the anomalous refraction is good as long as no other systematic error working in a similar way is present.The results, which are interpreted as an effect of the anomalous refraction by Pavlov and Sergijenko, could also be interpreted as a systematic instrumental error. It is furthermore maintained thatthe latitude and longitude of a field station can be determined in a few hours of one night if the premisses given in [3, p.68]are kept. It has been deplored that the determination of the azimuth has not been given the necessary attention. It is therefore proposed to intensify the research on this problem. The profession has been called upon to acquaint itself better with the valuable possibilities of astronomical determinations and to apply them in a useful and appropriate manner. At the same time, attention has been called to the possibility of improving astronomical determinations with regard to accuracy as well as effectiveness.

POINTING ACCURACY ON STARS

Abstract The accuracy of pointing to stars in astronomical observations for latitude, longitude and azimuth determinations with single-second and geodetic theodolites is investigated, especially with regard to the effect of the angle between the star's path and the crosswires and also the star's rate movement. The investigation includes 1440 observations to artificial stationary stars, nearly 5000 observations to real stars in preselected positions and also determination of circle graduation errors, personal equation etc. The results indicate that the two factors mentioned above do influence the pointing accuracy and that in selecting stars for precise astronomical determinations, the angle of the star's path deserves consideration.

POINTING ACCURACY ON STARS

The accuracy of pointing to stars in astronomical observations for latitude, longitude and azimuth determinations with single-second and geodetic theodolites is investigated, especially with regard to the effect of the angle between the star's path and the crosswires and also the star's rate movement. The investigation includes 1440 observations to artificial stationary stars, nearly 5000 observations to real stars in preselected positions and also determination of circle graduation errors, personal equation etc. The results indicate that the two factors mentioned above do influence the pointing accuracy and that in selecting stars for precise astronomical determinations, the angle of the star's path deserves consideration.

Time and Latitude in South Africa

In South Africa the modern outlook towards time may be said to have started in 1948. Both the two major observatories, The Royal Observatory in Cape Town and the Union Observatory (now known as the Republic Observatory) in Johannesburg had, of course, been involved in the astronomical determination of time almost from their inception, and the Johannesburg Observatory has been responsible for the official time of South Africa since 1908. However the pendulum clocks then in use could not be relied on to provide an accuracy better than about 1/10 second, which was of the same order as that of the astronomical observations. It is doubtful if much use was made of even this limited accuracy outside the two observatories, and although there may – occasionally have been a demand for more accurate time, it was certainly not voiced.

THE MATHEMATICAL BASIS OF RUSSIAN MAPS OF THE 18TH CENTURY

The author shows that in response to Peter the Great's policy of reorganization and modernization there were notable advances in Russian cartography during the 18th century, resulting in more accurate and more complete mapping of the country. She describes the procedures of district surveys, the methods, instruments, and expeditions for the astronomical determination of the coordinates of places, and the types of projections and scales used by general and particular maps and atlases.

Desiderata for Fk5

A fundamental catalogue compiled from independent and differential observations of stellar positions at various epochs provides the fundamental system of positions and proper motions of the stars. The system ought to be compiled in such a way that it represents the inertial frame of reference as accurately as practicable. Its direct purpose is to serve as the reference system of positional astronomy. It should fulfil the requirements of astronomical research, in particular in celestial mechanics and galactic research, as well as the demands of the astronomical determinations of time and of latitudes. It has also to fulfil the requirements of geodesy and navigation. For all these purposes the system must be uniform over the whole sky (free from regional systematic errors), and it has to be uniform over a large range of stellar magnitudes (free from errors depending on the magnitude of the stars).

A simple method of lunar surface navigation

The basic parameters used for the astronomical determination of the position of an observer on the lunar surface with sufficient accuracy for navigational purposes are discussed. Suggestions are made pertaining to the structure of the Nautical Ephemeris for the Moon. The observation consists of measuring the altitudes of a pair of stars which have approximately 90° difference in azimuth. For the determination of the accurate position it is not necessary to know the approximate position. Also the graphical system of position lines is not used. All operations are strictly numerical, though they can be performed by means of analog equipment of the type, for example, of Bygrave's slide rule.

PRECISE ASTRONOMICAL LONGITUDE DETERMINATIONS IN AUSTRALIA

AbstractThis paper is based on astronomical longitude determinations made at eight Laplace stations in South Australia and their subsequent calculation. The observations were made with a Wild T4 Universal Instrument and standard accessories.

Exact Determination of the Lunar Mass by means of Selenoid Satellites

As is well known, the astronomical determination of the mass of the Moon has so far been accomplished by methods based on the observation of the terrestrial nutation of the motion of the centre of the Earth around the centre of mass of the Earth–Moon system, and from the perturbation of the asteroid Eros.

Time and frequency standards

1. A periodic adjustment of fq against fm represents the first stage of application of molecular generators for controlling and checking fq, when it was necessary to keep that frequency within certain measurement limits γq, thus satisfying the frequency measurement requirements. For the purposes of time-keeping the use of this method is not promising since it does not ensure the use of molecular clocks with an error limited to the error of molecular generators, especially if the stability of fm is further increased. 2. Of the various methods of continuous automatic adjustment or measuring of fq against fm, the APC system and integral measurements are preferable since they provide actual and analytical molecular clocks with an error which is determined over a long time period by the error of fm, thus providing the most uniform time and frequency scale. 3. The raising of the stability of fm over a long period of continuous operation can be achieved in the first place by decreasing the effect of the molecular generator parameters, by making the generators work under optimum conditions and controlling automatically the values of these parameters, i.e., the temperature of cavity circuits, voltage of the focusing device and beam pressure. 4. One of the basic requirements of a molecular as well as any other clock is its continuous prolonged operation. The simple conditions of their utilization make molecular clocks suitable for use in the time and frequency service for the purpose of keeping reference time and frequency. In this connection any further development of molecular generators should be aimed at eliminating the use of frozen ammonia and of continuously operating prevacuum pumps. 5. Further improvements in molecular clocks may lead to their becoming the basic time-keepers, working standards, of time and frequency, whose actual value will be determined from astronomical observations. These measurements are necessary because the oscillation frequency of the molecular generators is unstable and can over a long period of time lead to certain relative errors Srm of the clock. In order to measure this error against the primary standard, the ephemeris time, it is necessary to select a long period of astronomical observations so as to make Srm≅3α0, whereα0 is the relative error of the astronomical determination of this time interval. If there exist molecular clocks whose relative error over a long period does not exceed 1·10−11, the actual value of their indications would have to be determined, considering the present accuracy of astronomical measurement, over a period of several dozen years.

Comparison of Astronomical Time Measurements with Atomic Frequency Standards

ATOMIC frequency standards have been in regular operation in several laboratories for the past few years. It has rapidly become clear that they can be used for comparisons with astronomical time determinations.

Preliminary determination of the dimension of the earth from the results of Chinese triangulation

The Central Land Surveying Bureau of China established several arcs of principal triangulation during 1932–37. Those which were completed before the outbreak of the war in July, 1937, are Nanking‐Anking, Nanking‐Hsüchow, Anking‐Nanchang, Nanchang‐Kiukiang, and Anking‐Wuchang arcs.At the end of each arc, a base line was measured with invar tapes or wires and an astronomical station at which latitude, longitude, and the azimuth to an adjacent station were determined by astronomical observations. The methods used in the astronomical determinations were the same as those used by the United States Coast and Geodetic Survey, that is, latitude by the Talcott method, longitude by wireless time‐signals, and azimuth by observing Polaris. The probable errors of these astronomical determinations were below ±0.″1 for determinations of latitude, ±0.″1 for determinations of longitude, and ±0.″4 for determinations of azimuths.