Exploring the influence of various factors on microwave radiation image simulation for Moon-based Earth observation

Abstract

Earth observation technologies are important for obtaining geospatial information on the Earth’s surface and are used widely in many disciplines, such as resource surveying, environmental monitoring, and evolutionary studies. However, it is a challenge for existing Earth observation platforms to acquire this type of data rapidly on a global scale due to limitations in orbital altitude and field of view; thus development of an advanced platform for Earth observation is desirable. As a natural satellite of the Earth, placement of various sensors on the Moon could possibly facilitate comprehensive, continuous, and long-term observations of the Earth. This is a relatively new concept and the study is still at the preliminary stage with no actual Moon-based Earth observation data available at this time. To understand the characteristics of Moon-based microwave radiation, several physical factors that potentially influence microwave radiation imaging, e.g., time zone correction, relative movement of the Earth-Moon, atmospheric radiative transfer, and the effect of the ionosphere, were examined. Based on comprehensive analysis of these factors, the Moon-based microwave brightness temperature images were simulated using spaceborne temperature data. The results show that time zone correction ensures that the simulation images may be obtained at Coordinated Universal Time (UTC) and that the relative movement of the Earth-Moon affects the positions of the nadir and Moon-based imaging. The effect of the atmosphere on Moon-based observation is dependent on various parameters, such as atmospheric pressure, temperature, humidity, water vapor, carbon dioxide, oxygen, the viewing zenith angle and microwave frequency. These factors have an effect on atmospheric transmittance and propagation of upward and downward radiation. When microwaves propagate through the ionosphere, the attenuation is related to frequency and viewing zenith angle. Based on initial studies, the simulation results suggest Moon-based microwave radiation imaging is realistic and viable.