English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

was director (see p. 112 of this issue). The work has been largely on stellar spectroscopy. Since 1936 the principal lines of work have been the development of methods of measuring stellar gradients and colour temperatures, using the McLean prismatic camera., and a photographic survey of galactic clusters ma.de with the Mond telescope. New ground has been broken in recent years with the initiation of photometric research on the twilight luminescence of atmospheric sodium. The Kensington telescope has been used to study the irregular variable star, y-Ca.ssiopeire; there are some 460 spectrograms of this star in an almost unbroken sequence from 1921 to 1956. The Observatory was, and is, maintained as a nonprofit making corporation through endowments and funds provided by donors. Since 1948 the management has been vested in the Council of the Corporation on which the University of Exeter has a definitive majority. The funds available have never been lavish. Rapidly rising costs since the War, together with the development of sophisticated experimental techniques, have meant that the position of the Observatory as an effective centre of original research has become progressively more difficult and indeed critical. Against the background of developments in satellites and in space research, the extensive recent progress of studies of the upper atmosphere and the revival of interest in astronomy and astrophysics, such a difficult position presents an obvious challenge. The site is large enough for astrophysical work and for an extensive programme of research and teaching in geophysics, a growing interest of the University's Department of Physics, and of geomagnetism, an interest of the Department of Mathematics. The first immediate change of activity for the Observatory will follow from the interests of Dr. K. Weekes and Mr. A. Nichol. Conditions in the high atmosphere can be studied by various means using both radio and optical techniques. Up to the height of the greatest electron concentration in the F • region it is possible, in principle, to infer the distribution of ionization from routine soundings. Above the peak of the F • region, artificial satellites may be used, or Thomson scattering of radio waves and optical experiments. An examination of the radio waves emitted by satellites may be used to infer the integrated electron density between the receiver and the satellite. This is relatively insensitive to the distribution of electrons, but as the satellite changes height in the course of a. transit, the distribution at satellite height may be inferred. The most valuable direct means of studying the distribution of electrons in the high atmosphere is by the Thomson scattering of radio waves by free electrons. Examination of experiments in the United States to heights of a.bout 700 km. suggests that useful results should be obtained to a height of about 2,000 km. It is commonly believed that the emission lines of OI at 6300 and 6364 A. are excited by recombination in the F region. The correlation between the optical intensities and radio measurements of ionization clearly must be examined. Moreover, it is possible, with careful techniques, to measure the line-width of the OI lines and so obtain a direct measure of the temperature of the atmosphere at the height of emission of these lines. To a classical astronomer nowadays anything below a fixed star is no doubt to be termed 'terrestrial', just as to many people any study above roof-level is termed 'astronomical'. The future is seen to lie in the wedding of optical with radio techniques in the fields of astrophysics and geophysics and of geomagnetism. Moreover, the vitality of the Observatory has suffered from its relative isolation. The University did indeed, so Gregory said, acquire "a possession which is unequalled in any but the older universities". The means a.re there to train students and research workers in the old and in the new techniques of exploring space. The raw material of research is to hand. The Observatory began as Lockyer's hobby in his old age: it has acquired a reputation in astrophysics and an affectionate regard in the south-west of England. By acquiring additional eyes we shall see more and see farther. An old man's hobby has become a young University's opportunity.

Long-Range Radio Communication by Satellite Microwave Dipoles