Results of radar observatlons of tho Orionid and Eta Aquarid meteor showers carried out In Budrio (Italy) wlthin the IHW program are compared with the simultaneous data from Ondřejov
(Czechoslovakia). The activlty of these showers Is studied in the relation to the motion of large particles ejected from the comet. The activity was found to be independent on tho approach of the parent comet.
Critical analysis of the results of space experiments, taking into account the contributlon of large particles to the total mass production of comet Halley leads to much higher values of the dust production rate than those derived from the first analysis of space measurements. As a consequence it seems necessary to correct the gas to dust ratio of the mass production by a factor of 10, from 0,1-1,0 to 1.0-10. The corrected values of dust production rate are in much better agreement both with the current concepts of the comeťs history and wlth the evolution of Its meteor stream.