velocity of such movement is of the order of 2 km second-1 which is in reasonable agreement with other available estimations of velocity of the auroral forms. The examples in Figures 1, 2, 3 and 4 show the capabilities of the BIZON to perform as a reliable ionosonde in an ionospheric network as well as a modern research ionosonde. Another conclusion which can be derived from the BIZON testing is that its technical reliability is rather high. This is a very important quality of an ionosonde proposed for performance in severe and uncomfortable conditions at polar observatories. 11.5. Availability Everybody who is interested in obtaining this type of ionosonde is encouraged to contact the manufactures of the BIZON .