Bondi-type systems near spacelike infinity and the calculation of the Newman-Penrose constants

We relate Bondi systems near spacelike infinity to another type of gauge co nditions. While the former are based on null infinity, the latter are defin ed in terms of Einstein propagation, the conformal structure, and data on s ome Cauchy hypersurface. For a certain class of time symmetric space-times we study an expansion which allows us to determine the behavior of various fields arising in Bondi systems in the region of space-time where null infi nity touches spacelike infinity. The coefficients of these expansions can b e read off from the initial data. We obtain, in particular, expressions for the constants discovered by Newman and Penrose in terms of the initial dat a. For this purpose we calculate a certain expansion introduced by Friedric h [J. Geom. Phys. 24, 83-163 (1998)] up to third order. (C) 2000 American I nstitute of Physics. [S0022-2488(00)02602-5].