The principal recommendations of this Report on the system of astronomical constants are in accordance with the resolutions passed at Symposium no. 21 (Paris, May 1963). We first of all give a reference list of the constants of the system and a set of explanatory notes. We have used the term ‘primary constant’, rather than ‘fundamental constant’, since the latter has a connotation in astronomical usage that is inappropriate to the manner of selection of the primary constants. In choosing the values for the primary constants we have, perhaps, adopted a conservative view of the likely errors of their determinations, but even so the new system should be of adequate accuracy for astronomical studies for many years. Limits within which the true values are believed to lie are indicated in a later section, in which we also give expressions for differential corrections to the derived constants. Finally we discuss the manner in which this system should be introduced into the national and international ephemerides.

The Chairman, W. Fricke, President of Commission 4, opened the Joint Discussion by drawing attention to the purpose and proposed procedure for the meeting. The Joint Discussion had been arranged by the Executive Committee of the Union in order to avoid the necessity for separate discussions by each Commission that was affected by the Report of the Working Group on the IAU System of Astronomical Constants. The Organizing Committee therefore proposed the following resolution:

The Chairman, W. Fricke, President of Commission 4, opened the Joint Discussion by drawing attention to the purpose and proposed procedure for the meeting. The Joint Discussion had been arranged by the Executive Committee of the Union in order to avoid the necessity for separate discussions by each Commission that was affected by the Report of the Working Group on the IAU System of Astronomical Constants. The Organizing Committee therefore proposed the following resolution:

The Chairman, W. Fricke, President of Commission 4, opened the Joint Discussion by drawing attention to the purpose and proposed procedure for the meeting. The Joint Discussion had been arranged by the Executive Committee of the Union in order to avoid the necessity for separate discussions by each Commission that was affected by the Report of the Working Group on the IAU System of Astronomical Constants. The Organizing Committee therefore proposed the following resolution:

The Chairman, W. Fricke, President of Commission 4, opened the Joint Discussion by drawing attention to the purpose and proposed procedure for the meeting. The Joint Discussion had been arranged by the Executive Committee of the Union in order to avoid the necessity for separate discussions by each Commission that was affected by the Report of the Working Group on the IAU System of Astronomical Constants. The Organizing Committee therefore proposed the following resolution:

Radar echoes have already been detected from Venus, Mercury, Mars, and Jupiter. Time delay measurements of high precision between Earth and Venus, as well as between Earth and Mercury, have disclosed significant deviations from the published ephemerides of these planets. Although new simultaneous solutions for the A.U., the relevant planetary masses, radii, and orbital elements have not yet been carried out, preliminary analysis indicates that the light-second equivalent of the A.U. is 499.0050 ± 0.0004 and that the corresponding kilometer equivalent is about 149 598 000 ± 100 (using c = 299 792.5 km/sec). The same analysis shows that, with respect to Earth, both Venus and Mercury seem to be ahead in their orbits relative to predictions. The radius of Venus appears to be about 6100 ± 50 km, in agreement with the most accurate optical determination. Doppler spread measurements show Venus to have a retrograde rotation with a period of about 247 ± 5 days. The celestial latitude of its axis is about – 85 ± 2 degrees.