On the prediction of F-layer penetration frequencies

The Comité Consultatif International des Radiocommunications (C.C.I.R.) predictions of F-layer penetration frequencies have been compared with 1963 Alouette topside-sounder data. The data used for these comparisons were collected from 45° to 165°W longitude in the northern hemisphere. It was found that the C.C.I.R. predictions differ by as much as 0.7 MHz from the Alouette data. The latitudinal and longitudinal variations could be represented more accurately in the C.C.I.R. prediction system by supplementing the ground-based ionosonde data with topside-sounder data.