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The Moon is a potential new platform for Earth observation. The advantages of its large-scale observational scope, long temporal duration, and multi-layer detecting of the Earth will undoubtedly advance our understanding of the Earth system. To carry out the observations from a Moon-based optical sensor, the geolocation error caused by exterior orientation elements need to be investigated. This paper analyses the error effects of exterior orientation elements on geolocation for an optical sensor. To estimate the error, we present a geometric image model and utilise some parameters to measure the image offsets. Through a large number of numerical simulations, the results demonstrate that the image offsets are not obvious influenced by the distance and observation angle at mid-high latitude of the Moon and have linear correlation with the increasing errors of the exterior orientation elements. Further, the relationship between the spatial resolution and errors of exterior orientation elements are revealed. Finally, the error characteristics for Moon-based Earth observation are discussed. It is expected that the conclusion drawn in this paper could support the study of a Moon-based Earth observation optical sensor. [ABSTRACT FROM AUTHOR]

The Moon, Earth's only natural satellite, is a potential new platform for Earth observation. Moreover, with the wide applicability of the angular information from remote sensing data, it has been attracting increasingly more attention. Accordingly, this study focuses on the angular characteristics of Moon-based Earth observations. Using ephemeris DE430 and Earth orientation parameters, the position and attitude of the Sun, Earth, and Moon were obtained and their coordinates normalized to a single framework using coordinate transformations between the related reference systems. Then, an angular geometric model of Moon-based Earth observations was constructed, and the corresponding angular algorithms were presented. The results revealed the angular range and distribution characteristics of Moon-based Earth observations. For every point on the surface of the Earth, the view and solar zenith angles all vary widely, which decreases with increasing latitude. The view and solar zenith angles all vary widely with the largest range of values in the equatorial and polar regions and a smaller range of values in mid-latitudes. Furthermore, the range of solar angles of Moon-based Earth observations is the same as that of all-time solar angles, indicating the potential for monitoring and understanding large-scale geoscientific phenomena using Moon-based Earth observations. [ABSTRACT FROM AUTHOR]

As the earth's only natural satellite, the Moon has unique advantages as an earth observation platform because of its long observation distance and the vast expanse of the lunar surface. To observe the earth from the Moon, the looking vector direction and its variation regularity need to be investigated. In this paper, we first establish a Moon-based earth location algorithm to reveal the variations of the looking vector. In this algorithm, assuming the sensor points to the earth, the looking vector expressed as azimuth and elevation angles is calculated, and the intersection point between the looking vector and the earth's ellipsoid is solved using the relevant equations. The mathematical expression of the observational scope is also derived so as to determine the looking vector range if the looking vector direction is limited in the earth disk. Based on this algorithm, we describe the earth's motion in the lunar topocentric coordinate system and analyze the looking vector direction characteristics by assuming different positions on the lunar surface. In addition, the earth location error is evaluated by adding the looking vector errors. The results show that sensors at different positions on the lunar surface have different looking vector pointing characteristics and different earth location errors. The earth location error is relatively small in the high-latitude region of the Moon. Combining the restriction of lunar local topography, we suggest that the regions that latitude between 30 °N and 80 °N or 30 °S and 80 °S are the ideal locations for the Moon-based earth observation platform. [ABSTRACT FROM AUTHOR]

Large-scale geoscience phenomena are increasingly attracting more attention because of their great scientific and social significance. However, many existing earth observation systems lack the ability to conduct long-term continuous observations at a regional-to-global scale because of spatial and temporal coverage limitations and systematic bias. In this work, we propose a new platform, the moon, and discuss its potential and optical geometrical characteristics for observing large-scale geoscience phenomena. Based on the Jet Propulsion Laboratory ephemerides, the reference systems transformation and a simulation system of moon-based earth observations were developed. Numerous experiments were carried out and a series of simulation images are presented, which illustrate the wide swath and continuous observation characteristics of such a lunar observatory. In order to quantify the performance of moon-based earth observations, a simplified geometrical model was constructed and data were analyzed. The sublunar points were found to be unique parameters with the ability to characterize the relative positions between moon and earth. We also defined an effective coverage parameter for assessing the optical coverage ability of moon-based earth observations. The calculation showed that the average value of the introduced coverage parameter from 1960 to 2050 was 0.500, and the coverage remained stable in different years. Furthermore, the total daily visible time and repeated times of different positions on the earth surface are analyzed and the effect of different positions on the lunar surface of the observatory are evaluated. The result shows that such a moon-based approach could make significant contributions to the monitoring and understanding of large-scale geoscience phenomena. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

The solar invasion to an Earth observation sensor will cause potential damage to the sensor and reduce the accuracy of the measurements. This paper investigates the effects of solar invasion on the Moon-based Earth observation sensors. Different from the space-borne platform, a Moon-based sensor can be equipped anywhere on the near-side of the Moon, and this makes it possible to reduce solar invasion effects by selecting suitable regions to equip sensors. In this paper, methods for calculating the duration of the Sun entering of the sensor's field of view (FOV) and the solar invasion radiation at the entrance pupil of the sensor are proposed. By deducing the expressions of the proposed geometrical relationship between the Sun, Earth, and Moon-based platform, it has been found that the key parameter to the effects of solar invasion is the angle between the Sun direction and the line-of-sight vector. Based on this parameter, both the duration and radiation can be calculated. In addition, an evaluation approach based on the mean value and standard deviation has been established to compare the variation of solar invasion radiation at different positions on the lunar surface. The results show that the duration is almost the same wherever the sensor is placed in the permanent Earth-observation region. Further, by comparing the variation of solar invasion radiation at different positions on the near-side of the Moon, we suggest that equipping sensors on the mid–high latitude regions within the permanent Earth-observation region will result in less solar invasion affects. [ABSTRACT FROM AUTHOR]