Abstract
Spatio-temporal characteristics are the crucial conditions for Moon-based Earth observations. In this study, we established a Moon-based Earth observation geometric model by considering the intervisibility condition between a Moon-based platform and observed points on the Earth, which can analyze the spatio-temporal characteristics of the observations of Earth’s hemisphere. Furthermore, a formula for the spherical cap of the Earth visibility region on the Moon is analytically derived. The results show that: (1) the observed Earth spherical cap has a diurnal period and varies with the nadir point. (2) All the annual global observation durations in different years show two lines that almost coincide with the Arctic circle and the Antarctic circle. Regions between the two lines remain stable, but the observation duration of the South pole and North pole changes every 18.6 years. (3) With the increase of the line-of-sight minimum observation elevation angle, the area of an intervisible spherical cap on the lunar surface is obviously decreased, and this cap also varies with the distance between the barycenter of the Earth and the barycenter of the Moon. In general, this study reveals the effects of the elevation angle on the spatio-temporal characteristics and additionally determines the change of area where the Earth’s hemisphere can be observed on the lunar surface; this information can provide support for the accurate calculation of Moon-based Earth hemisphere observation times.
Highlights
In recent years, Earth system science has considered the planet as an indivisible whole, with large-scale geoscience phenomena such as global warming receiving increasing attention
This study reveals the effects of the elevation angle on the spatio-temporal characteristics and determines the change of area where the Earth’s hemisphere can be observed on the lunar surface; this information can provide support for the accurate calculation of Moon-based Earth hemisphere observation times
The European Space Agency (ESA) proposed a project called Long-Term Data Preservation (LTDP), whose mission includes recording regional to global Earth observation data [5]
Summary
Earth system science has considered the planet as an indivisible whole, with large-scale geoscience phenomena such as global warming receiving increasing attention. Monitor, and predict global change, many countries and organizations have created three global observation systems These systems are named the Global Climate Observing System (GCOS), the Global Ocean Observing System (GOOS), and the Global Terrestrial Observing System (GTOS), and their objectives are to observe the climate, oceans, and land [1,2,3]. The European Space Agency (ESA) proposed a project called Long-Term Data Preservation (LTDP), whose mission includes recording regional to global Earth observation data [5]. These observations are all continuous and provide abundant data for revealing the potential mechanism of Earth system evolution. These projects demonstrate that studying Earth system science requires large-scale and temporally consistent data
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