In spite of the availability of satellites, the possiblity of increasing basic knowledge of cosmic radiation with the help of balloons has not diminished. New detection techniques have made it possible to enter new areas of study which had been closed earlier.
The use of stratosphere balloons in the study of primary cosmic radiation has been responsible for most of the progress made during the past 25 yr.
In spite of the availability of satellites, the possibility of increasing basic knowledge of cosmic radiation with the help of balloons has not diminished. New detection techniques have made it possible to enter new areas of study which had been closed earlier.
The main areas which have been opened up are (1) Extension of the study of the charge spectrum to include elements with abundances 103-106 times lower than those studied until now. This includes all elements between iron and uranium (and possibly beyond).
(2) Study of the isotopic composition of the elements already identified in the primary radiation.
There are, of course, other important areas of cosmic ray study where balloons are inadequate and satellites are necessary, such as
(3) Investigation of the energy range above the geomagnetic sensitive region (energy spectrum, chemical composition, positron-electron ratio, search for anti-nuclei).
(4) Investigations in the very low energy region, where even a small amount of residual atmosphere cannot be tolerated (chemical and isotopic composition, positron and electron spectra, modulation effects).
(5) Interplanetary intensity gradients. (6) Monitoring the emission of solar 'cosmic' rays.
Nevertheless, the problems listed under (1) and ( 2)justify an intensification of effort in balloon instrumentation for reasons which are quite general and can be formulated as follows:
Galactic cosmic ray nuclei represent the only sample of matte, r available to us which does not belong to the solar system. Its uniqueness in this respect is not likely to change in the foreseeable future.
Leaving aside information derived from cosmic rays, present knowledge of the composition of matter in the universe is based entirely on electromagnetic radiation emitted or absorbed by atoms and molecules.
This source of information, although enormously rich and diversified, is, nevertheless, deficient in at least two major respects: