Cosmic-ray intensity at Thule, Greenland, during 1962 and 1963 and a comparison with data from Mariner 2

During each of the summers of 1962 and 1963 six balloon flights were made at Thule, Greenland (geomagnetic latitude 88°N), in continuation of a program to follow the secular changes in primary cosmic rays. Similar flights at Thule have been made during most of the years beginning in 1951. The flights have usually extended over a period of at least two weeks to be sure that transient effects will be minimized. Following the substantial increase from 1961 to 1962 of 20 per cent at high altitudes, a much smaller increase of 7.5 per cent occurred between 1962 and 1963. Three weeks after the last night at Thule in 1962, data had started to be received from the Venus probe Mariner 2. This vehicle had aboard an ionization chamber that had been compared with the balloon-borne chambers, both with γ rays and with cosmic rays at high altitudes. From a comparison of the data from the two instruments a value of 21 per cent is derived for the albedo effect at the top of the atmosphere at Thule.