The appended reports of the directors of the national ephemeris offices provide a record of the current activity in the publication and preparation of astronomical ephemerides, including those published for use by navigators and surveyors and those prepared for astronomers whose special needs are not met in the printed almanacs. A brief review of the relevant work of other institutions and individuals is also given in the appendix. The reports also cover to some extent activities in positional astronomy and celestial mechanics (i.e. in the fields of interest of Commissions 7, 8, 17, 19, 20 and 31). This report is therefore restricted to reviewing, firstly, the action that has been taken on matters raised at and since the 1967 meetings of the Commission and, secondly, the matters that will require attention at and after the 1970 meetings.

Before that review, it is appropriate to pay tribute to the memory of that almost legendary astronomer, Gaston Fayet, who died on 27 December 1967 at the advanced age of 93. As member of the Bureau des Longitudes responsible for the production of the Connaissance des Temps from 1930 to 1961, and President of Commission 4 from 1938 to 1952, he contributed greatly to our subject, in addition to his researches in other fields particularly in respect of the minor planets.

During the period under review two issues of the Astronomical Yearbook of the U.S.S.R. for the years 1971, 1972 have been published, and that for 1973 is in preparation. The positions and proper motions of the stars are in the FK4 system as recommended by Commission 4 in 1961. Further, as recommended at the meeting in Hamburg in 1964 (Trans. IAU, 12 B (1964), 105,1966) the IAU System of Astronomical Constants has been introduced into the tabulations of the day numbers, solar and lunar eclipses, ephemerides for physical observations of planets, and the factors S &C. The corresponding differential corrections to the Moon’s ephemeris as well as re-calculated eclipse data for 1971 have been tabulated separately in the Appendix to the Yearbook for 1971. As from the edition of the Yearbook for 1972, the lunar ephemeris j = 2 will be published in accordance with the recommendations adopted in Prague in 1967.

The regular publication of the ephemeris of the lunar crater Mösting A has been continued in the editions of the Yearbook mentioned above.

Fundamental ephemerides of the Sun, Moon, and planets have been printed in full conformity with the first part of the Astronomical Ephemeris circulated in advance by H. M. Nautical Almanac Office, Royal Greenwich Observatory.

The operation of the Central Bureau for Astronomical Telegrams, thanks to the diligence of its Director and his collaborators, has continued to remain relatively tranquil and quite effective since January 1968, following the methodology established by the previous Director, Dr Owen J. Gingerich. Financial problems, temporarily at least, seem not to be of major concern. The effective subsidy by the Smithsonian Astrophysical Observatory has been reduced almost to a tolerable level. Policy with regard to the content of the Circulars, however, deserves continuing surveillance by the subscribers.

The most exciting feature of contemporary celestial mechanics is the close interaction with three of the most dramatic engineering achievements of our time: the electronic computer, artificial celestial objects, and the precise measurement of distances in the solar system. The last two provide new information for and make new demands on celestial mechanics and the former provides an effective means of response. These developments have also stimulated people with backgrounds other than celestial mechanics to make contributions in the field.

Since the last meeting of the Union, the use of the computer for literal theoretical developments has become effective and widespread.

The creation of artificial celestial objects not only requires the services of celestial mechanics but provides the means of obtaining new measurements that may throw light on the physical laws that govern the motion of celestial objects. In other words, we can now perform experiments as well as observe.

It is with deep regret that we mention the death, on 15 July 1969, of Prof. Dr G. Demetrescu who has done so much for the development of Astronomy in Roumania.

This report is based on letters received from members of the Commission, whom I wish to thank most cordially.

The most important events in the development of positional astronomy during the three past years were:

1. (1) The construction and use of new types of astronomical instruments based on new techniques, and

2. (2) The collective observations of large numbers of stars, especially in the Southern hemisphere on the basis of international cooperation.

At the USNO a design study for a ten-inch automatic meridian circle (ATC)was completed in 1968. Construction and installation should be completed by the end of 1970. A modified Cassegrainian optical system with a Cer-Vit primary mirror is being used. For some other important parts of the instrument new materials will also be used. At each end of the horizontal axis of the instrument Inductosyns will be mounted.

An Inductosyn system for digital readout of the pointing angle of the telescope was installed on the six-inch transit circle of the USNO in 1967 for testing and calibration. An IBM-1800 data acquisition and control system was on line with the same instrument.

Le présent rapport ressemblera peu à ceux présentés aux précédentes Assemblées Générales de l’Union; d’abord en raison des prescriptions du Comité Exécutif concernant la limitation du texte, la suppression des références bibliographiques et la latitude laissée au Président dans la conception même du Rapport; ensuite parce qu’il est apparu que la Commission 9 avait un rôle et une position assez différents de ceux de la plupart des autres Commissions et que l’un des points auxquels il convenait de s’attacher était précisément le re-modelage de son activité.

Toutefois, un certain nombre de membres de l’Union ayant bien voulu résumer l’activité de leurs Institutions ou de leurs pays dans le domaine de l’instrumentation astronomique, leurs contributions trouveront place dans le présent Rapport et fourniront ainsi aux membres de l’Union une information non exhaustive mais cependant des plus utiles, en attendant que soit mise au point une nouvelle forme de documentation.

Enfin, l’un des groupes de travail de la Commission - sur les Tubes à images - ayant poursuivi son travail de coordination et d’information comme par le passé, un rapport spécial sur son activité figurera à la suite du Rapport Général de la Commission 9.

Bien que ce groupe n’est pas été formellement dissous, on doit constater qu’à part une séance lors de l’Assemblée Générale de Hambourg, aucune activité dans le cadre de l’UAI ne s’est manifestée dans ce domaine depuis le Symposium No. 19, tenu à Rome en 1962. Cette réunion répondait à un besoin et le volume de ses Comptes-Rendus a suscité un intérêt certain. Mais au-delà, chacun des groupes intéressés à une prospection a organisé son travail selon ses propres conceptions, en fonction des conditions géographiques qui lui étaient fixées et des moyens matériels mis à sa disposition. Il en résulte que si les méthodes d’évaluation de la qualité des images ont été quelque peu passées au crible de la critique internationale, peu de progrès ont été faits dans le sens d’une comparaison significative à l’échelle mondiale entre des sites inclus dans des campagnes de prospection différentes. Force est bien de regretter ce non-aboutissement, tout en accordant aux responsables des divers opérations l’excuse du délai généralement limité qui leur est imparti, et l’impossibilité d’attendre la mise au point d’une normalisation internationale. Un “groupe interne” de la Commission 9, au sens défini dans la première partie de ce Rapport, pourrait se consacrer à cette importante question.

Un article de synthèse a été publié par Kent Ford en 1968 (1). De plus, le 4ème Symposium international sur les récepteurs photoélectriques d’images s’est tenu à Londres en Septembre 1968 et les comptes rendus des communications paraissent actuellement (2); il y sera fait référence par la mention (AE, page).

Il est espéré que les travaux omis involontairement et les développements nouveaux pourront être présentés lors des séances de la Commission 9 à Brighton.

Le rapport considère les trois types principaux de récepteurs: ceux qui emploient l’électronographie, ceux qui utilisent un écran fluorescent (convertisseurs d’images) et enfin les appareils de télévision.

The reader is kindly asked to consider this report for some sort of greatly unbalanced equilibrium between the pressure exercised by the steadily increasing flow of papers discussing the vastly extending subject of solar activity, and the equally steady pressure exercised by the editor who insists on having this report twice as short as three years ago. Therefore, some selection of the subjects and papers had to be made, a fairly severe one, since only about one third of all published papers could have been mentioned in the references, and I am well aware that almost everyone who will read the report, could suggest some improvement of the selection scheme. Nevertheless, I believe that the report as it stands, can fulfill its basic purpose, i.e. to give to the readers a general picture on the progress, which has been achieved in the field of solar activity research since the Prague meeting and on some of the research activities which are in progress at the present time.

It is a great pleasure to acknowledge the enormous help I have received from the authors of the individual sections of the Draft Report, as well as from many other members of the Commission, who have very kindly provided me, or the co-authors, with useful information on the recent progress of their work. It is necessary to add that some highly valuable comments made by V. Bumba, J. T. Jefferies, C. Sawyer, E. v. P. Smith, B. Valníček and J. M. Wilcox, have also been included in other chapters than those prepared by themselves.

By action of the Executive Committee of IAU, the report for 1970 is restricted to half the length of the 1967 draft report; the bibliography and the abstracting of work already published are essentially eliminated. The report is no longer to serve primarily as a review of accomplishments between General Assemblies but rather as a report of work in progress. These changes were adopted by the Executive Committee in order to reduce the cost of publishing the reports.

Several commission members have voiced the opinion that the extensive bibliographies in past reports have been the most valuable contributions of the reports and they have objected to the elimination of the bibliography. Also, material from some observatories and from some national groups that have been submitted for inclusion in this draft report have contained only abstracts of work already published. The rules adopted by the Executive Committee do not permit the report to abstract published works except in evaluating general progress in solar astronomy. We express our regret to these commission members and to these institutions that we have not been able to include the abstracts and bibliography in the present report.

Of a select list of about 40 Fraunhofer lines distributed between λλ 3083-7122, central intensities corrected for scattered light, ghosts and instrumental profile, has been obtained for 18 lines. Uncorrected values of central intensity for a number of other lines are available. A complete list of the results of all observers will be given at the General Assembly in Brighton.

The working Group on Solar Eclipses regrets Dr J. Houtgast’s resignation as Chairman of the Group. However, Dr Houtgast will maintain his membership and continue to give his experience to the group.

The total eclipse of September 22,1968 was actively observed by many groups in spite of its short duration. Reports on the observations are expected to be given during the 1970IAU General Assembly.

A great deal of work has been done everywhere in view of the total eclipse of March 7, 1970.

Experiments on Lamb-dip stabilization of the 6328 Å He-Ne laser line made at NBS, NPL and PTB and reported in a joint paper (10) show that the wavelength from different lasers may differ by as much as one part in 107. Similar work on a C02 laser line at 10.6 μm and a xenon line at 3.5 μm is reported from NPL, the 1.15 μm line in a pure Ne 20 laser has been investigated at JILA (5), and several lines in a xenon ion laser are being studied at PTB. However, the method that holds the greatest promise of accuracy and stability is the use of saturated absorption to lock a laser wavelength to some molecular transition having a sharply defined and stable wavelength. Thus the 6328 Å He-Ne laser line can be fixed on a line in the molecule 127I2 (6, 7), and the 3.3913 μm line of a He-Ne laser has been connected to a line of CH4, promising a unique precision and stability according to experiments made at JILA (5) and NRC. This technique will evidently yield excellent substitutes for the Kr 86 line, and may, when the time is ripe, lead to the adoption of an improved primary standard.

A very great deal of work has been done during the last three years on the determination of atomic transition probabilities, and complete coverage here is impossible. Wiese and his staff at the National Bureau of Standards, Washington, have continued to collect all numerical results, and they can supply information as to what is available for any particular atom. They have published (1) a critical compilation of atomic transition probabilities for the atoms sodium to calcium (inclusive) in essentially the same way as an earlier compilation covered hydrogen to neon. At the time of writing a complete new bibliography is also in preparation (2), which will be published as NBS Special Publication 320 and which is complete up to June 1969. Review articles published include that of Layzer and Garstang (3) on theoretical allowed and forbidden transition probabilities, and the two volume conference report (4) covers beam foil spectroscopy (including lifetime measurements) in some detail. A fairly complete review of forbidden line transition probabilities was given by Garstang (5), where references to many original papers may be found. In the following we shall confine ourselves to mentioning a few areas of particular interest; detailed references can be traced through the bibliographies, reviews and abstracting journals.

Two review articles have been published (1,2).

1.1. Collision broadening by neutral atoms. The continued study of widths and shifts produced by neutral atom impacts at low densities has shown that the Van der Waals interaction ( — C6r−6) as used, for example, in (3), is an inadequate representation of the interatomic potential. The classical theory for a Leonard-Jones potential (C12r−12 — C6r−6) has been developed (4) and subjected to experimental test (5). Further improvements result from introducing a term C8r−8 in the potential (6) and from allowance for quasi-static effects (7). Applications to broadening by H—atom impact are discussed in (8).

A current Bibliography on The Analyses of Optical Atomic Spectra is in print (43). It appears in four sections, three of which cover the same elements as the respective volumes on Atomic Energy Levels. Relevant literature references from the dates of publication of these Volumes are continued for each spectrum to the present, as follows:

The last Section contains references to rare-earth spectra:

The present report will be limited to later work.

The laboratory study of molecules of interest to astrophysicists has been progressing at a steady pace. A complete bibliography for the year September 1968 to September 1969, for instance, would show work on 68 molecules of possible interest; the diatomic and simpler polyatomic molecules. During this period 38 papers appeared on H2 alone, notably on its polarizability and the character of its spectrum near the ionization limit. Twenty-one papers on CO included studies in the vacuum UV, its Franck-Condon factors, chemiluminescence and IR absorptances. In the interests of saving space in this report, the detailed discussion of published work on each molecule of interest will be deleted. Instead, attention might be called to the fact that a complete card file bibliography is maintained by Phillips at Berkeley, and inquiries are welcome. In addition, a bi-monthly Newsletter is distributed from Berkeley in collaboration with S. P. Davis of the Physics Department.