Nature 175, 78 - 79 (08 January 1955); doi:10.1038/175078a0

Radio Astronomy in Hawaii

GROTE REBER

Wailuku, Maui, Hawaii. Oct. 12.

SINCE early 1953, observations of cosmic static have been made at an altitude of 10,020 ft. from the top of Haleakala volcano on the island of Maui in the Hawaiian archipelago near lat. 20° N. A Lloyd's mirror technique is used with frequencies near 20, 30, 50 and 100 Mc./s. The anomalies introduced by the ionosphere at the first three frequencies are so great that most of the results are unintelligible. At 100 Mc./s. the situation is sufficiently simple to be partly understood. Sources with discontinuities of surface brightness small compared to a minute of arc produce rapid interference patterns. Smooth sources of larger angular width produce much slower diffraction patterns. The hours of darkness provide the best results. During the day, radiations from the sun stir up the topmost parts of the atmosphere far above the F-layer. This situation manifests itself as great absorption, probably due to scattering, especially during the afternoon hours. Thus there is a marked diurnal effect. This diurnal effect is least on far northern sources and increases rapidly in magnitude and duration as sources of lower declination are observed. Obviously, there is also an azimuth effect.