Since the first conception of a hovercraft by C. S. Cockerell in the early 1950s, and the completion of the first experimental full-scale machine (SR. N1) in 1959, the development of these vehicles has advanced to the stage of practical use.

The ionosphere is a thick mantle of partly ionized gas surrounding the earth at heights between 80 and 800 km. It was discovered about fifty years ago, and during the last decade has been studied intensively at observatories all over the world. These studies consist primarily of observing the characteristics of radio waves reflected from the ionosphere. Since waves of different frequencies are reflected at different heights, it is possible to determine how the electron density varies with height, up to the height of maximum density at about 300 km. Radio waves which pass this height, however, continue into space and are not reflected. Consequently very little direct information can be obtained from the ground about the characteristics and behaviour of the ionized region above 300 km.

Whenever man is shipwrecked and takes to a lifeboat or a raft, crashes in an aircraft, or gets into trouble mountaineering or on an expedition, he requires help and rescue. Before any action can be taken by potential rescuers it must be known that a disaster has taken place. At present such knowledge is often acquired in a negative manner, by non-arrival at an expected destination or loss of communication contact. Even if positive information is received by a distress message, the exact location of the incident is often in doubt. Extensive air searches are then required before a rescuer can be guided to the spot.

The conception of the sea as an unlimited reservoir of fish is now outdated. The post-war history of the fishery resources of the north Atlantic has shown that stocks can be depleted to a level where the catching rates are no longer an economical proposition, and the general pattern of expansion has been to move farther afield to grounds where the catches are sufficiently improved to offset the greater steaming time, and hence running costs, involved.

This report is intended to supplement the more general reports on the activities of the United States in the Antarctic which have appeared in the Polar Record, Vol 12, No 79, 1965, p 439–52 and earlier issues, and in BioScience, Vol 15, No 4, 1965.

During the 1959 activities of the International Glaciological Expedition to Greenland, tellurometer measurements of the geodetic traverse over the ice sheet were found to contain systematic errors of the order of 1 part in 105 in distance measurement, and there was a big loss in instrument range. The origin of these difficulties may lie in the large temperature gradient in the air close to the snow surface, or in the scattering of the signal from the rough surface, or in the propagation characteristics in the dielectric boundary layer between snow and air (Nottarp, 1962). We are concerned here with the practical solution to the difficulty—the use of a high antenna mounting—and with other modifications made to the instruments for use on the Ross Ice Shelf Survey, 1962–63.