Eppley Foundation for Research

Foundations have reporting requirements that must be followed, notes grant-director Ingrid Eisenstadter.

The paper is theoretical, based on experimental data. It treats field measurements of the circumsolar radiation in order to derive from them the variations of the turbidity of the atmosphere at the high level stations Table Mountain and Montezuma. A single relationship is derived for the circumsolar radiation as a function of the coefficient of turbidity beta.

The study reported on here is a continuation of an earlier investigation by the same authors into the relationship between natural illumination and shortwave solar radiation. Whereas the initial approach treated the illumination of sunlight as derived from the corresponding filtered direct radiation component, the results now given extend this work to parallel determination of the (more generally applicable) illumination of integral daylight on the basis of similarly filtered global (sun and sky) radiation. Characteristics are outlined of the instrumentation employed in the investigation undertaken at different locations, viz., Newport, Jerusalem (Israel), and Mauna Loa (Hawaii), as compared with the basic work that utilized data assembled at Pretoria (South Africa). Included is an extension to recent solar radiation measurements obtained on high-altitude aircraft. In general, it is established that it is possible to derive such estimates of natural illumination from radiometric measurements with an accuracy comparable with that obtainable in the best direct photometric efforts.

The authors have extended the work of Ångström & Drummond concerning the temperature dependence of the three meteorological standard filters (Schott OG 1, RG2 and RG8) and here give values of the temperature coefficient of the center of lower cutoff for seven other Schott sharp cutoff filters. The results demonstrate that there is a definite relationship between the normalized cutoff wavelength and this coefficient, the coefficient increasing semi-logarithmically with wavelength over the region 440–920 millimicrons.

An account is given of an investigation into the pressure dependence of the sensitivity (i.e., responsivity) of 10 different types of thermopile detector over the pressure range 760–10−5 mm. The study is confined to those forms of thermopile commonly used for the measurement of unmodulated solar and infrared radiation. The radiation intensity-thermopile emf relationship at reduced ambient pressures is discussed, as is also the change introduced into the response-time constant. It is demonstrated that the results for the different instruments are in agreement, generally, with what is derived from the fundamental laws governing energy transfer within radiometric devices.