Technique of Observing the 5‐mm Self‐Emission From the Oxygen of the Earth's Atmosphere to Obtain a Vertical Sense

Abstract

The results of previous calculations have shown that, due to the heavy absorption of the atmospheric oxygen, the resultant radiation both in the wells and in the cores of the 60‐Gc/s spectral complex provides a radiometrically bright mantle surrounding the earth. It becomes evident when viewed from space that this oxygen mantle could supply a uniform, nonftuctuating signal for radiqmetric sensing.This paper presents a quantitative expression of a technique of observing the 5‐mm self‐emission from the oxygen of the earth's atmosphere in order to obtain a vertical sense. The choice of operating frequency is a selection process in which a frequency is determined for which the atmospheric opacity is great enough to reject the radiation from the lower atmosphere, and at the same time have sufficient transmissivity in the upper atmosphere to allow predominance of radiation from the 15‐ to 32‐km region. Under these conditions a uniform and well‐defined radiating disk should be seen. To the degree that the observed disk exhibits circularly uniform emission and the mantle possesses spherically homogene US density, the line through its center of brightness may be defined as the direction corresponding to the local vertical at the spacecraft. This may be determined as the boresight axis of a lobe comparison antenna system.