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Visibility of Moon-based platform. The lines of sight A2B1 and A1B2 are shown for an extreme case, calculated with the angle a between the two lines and the geocentric angle?
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As a new concept platform for Earth observation, a Moon-based platform has the advantages of large-scale, constant and long-term dynamic Earth observations that can meet the needs of conducting systematic research on the Earth. However, a Moon-based platform has particular differences from space-borne and air-borne platforms because of its long dis...
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... Visibility of the earth from Moon-based platform Different locations on the Moon have different views of the Earth. Visibility of the Earth from the Moon-based platform is a key aspect in determining the best location for a proposed Moon-based sensor system. We consider only if the whole Earth disc is visible in the Moon-based sensor field of view. This is also a prerequisite for the observation geometry. The Moon-based platform visibility geometry is shown in Figure 2. Using this criterion, we calculate the latitude and longitude range on the Moon where sensors can observe the Earth all the time (see Figure 3). The visibility on the Moon is constantly changing with the Moon and Earth's declination. Also, the observing range is characterized by the coordinates of the point N m . This fact, at variance with the satellite case, in which the sensors are at the geometric centre, leads to a great difference in observation views with respect to the Moon-based platform case. For instance, when the Moon-based sensor is located at the Moon's South Pole, the Earth's rising and setting can be seen from the Moon-based sensors, but when the sensors are placed at the Moon's Equator, the Earth is in the field of view all the ...
Citations
... A Moon-based platform has two major characteristics that differs from those of traditional Earth observation platforms. The first is its extremely long observation distance, which helps to observe Earth integrally Ye et al., 2017). Under such circumstances, sensors on the lunar surface, such as telescopes on the Earth's surface, characterize the planet by disk-averaged observations, similar to a point source without any spatial resolution. ...
A Moon‐based sensor can observe the Earth as a single point and achieve disk‐integrated measurements of outgoing longwave radiation (OLR), which significantly differs from low orbital, geostationary, and Sun–Earth L1 point platforms. In this study, a scheme of determining the disk‐integrated Earth’s OLR based on a Moon‐based platform is proposed. The observational solid angle was theoretically derived based on the Earth’s ellipsoid model and the disk‐integrated observational anisotropic factor was estimated to eliminate the effects of the Earth’s radiant anisotropy. The simulated disk‐integrated Earth's OLR obtained from a Moon‐based platform varies periodically, due to changes in the observation geometry and Earth's scene distribution within the observed Earth’s disk. Clouds, meteorological parameters, and the land cover distribution notably affect the disk‐integrated Earth’s OLR. By analyzing the disk‐integrated Earth’s OLR from a Moon‐based platform, significant variabilities were investigated. Additionally, the Earth’s shape and radiant anisotropy that affecting the disk‐integrated Earth’s OLR were estimated. In conclusion, a more realistic Earth’s shape, the latest version of the angular distribution model (ADM), and accurate land cover and meteorological datasets are needed when determining the disk‐integrated Earth’s OLR. It is expected the unique variability captured by this platform and its ability to complement traditional satellite data make it a valuable tool for studying Earth’s radiation budget and energy cycle, and contributing to diagnostic of the climate General Circulation Models (GCM) performance.
... The track of nadir points and altitude are often utilized to present the features of Earth satellites of different kinds of Earth orbits and play an influential role in the further performance of observation characteristics. The angular and spatiotemporal coverage characteristics are the two commonly concerned features in Earth observation, which have been studied carefully in many previous studies on Moon-based Earth observation [34,35]. Thus, the first step of this work is to compare the different performances of halo orbits in these aspects. ...
... However, when it comes to broadside-looking synthetic aperture radar (SAR), the incident angle and azimuth angle need to be limited for data quality. There are relatively many historical studies focused on the spatiotemporal coverage of Moon-based Earth observation [34,35]. In this section, the effects of the limitations of elevation angle and azimuth angle on the global spatiotemporal coverage of Moon-based SAR as well as the halo orbits are analyzed for comparison. ...
The unceasing quest for a profound comprehension of the Earth system propels the continuous evolution of novel methods for Earth observation. Of these, the Lagrange points situated in the cislunar space proffer noteworthy prospects for space-based Earth observation. Although extant research predominantly centers on Moon-based Earth observation and the L1 point within the Sun-Earth system, the realm of cislunar space remains relatively unexplored. This paper scrutinizes the overarching characteristics of the L1 point within the Earth-Moon system concerning Earth observation. A pivotal enhancement is introduced through the incorporation of the halo orbit. This research comprehensively analyzes the relative motion between the halo orbiter and the Earth, achieved via orbit determination within a rotating coordinate system, followed by a transformation into the Earth coordinate system. Subsequently, numerical simulations employing ephemeris data unveil the observing geometry and Earth observation characteristics, encompassing the distribution of nadir points, viewing angles, and the spatiotemporal ground coverage. As a point of reference, we also present a case study involving a Moon-based platform. Our findings reveal that the motion of the halo orbit, perpendicular to the lunar orbital plane, results in a broader range of nadir point latitudes, which can extend beyond 42°N/S, contingent upon the orbit’s size. Additionally, it manifests a more intricate latitude variation, characterized by the bimodal peaks of the proposed temporal complexity curve. The viewing angles and the spatiotemporal ground coverage closely resemble those of Moon-based platforms, with a marginal enhancement in coverage frequency for polar regions. Consequently, it can be deduced that the Earth observation characteristics of the L1 point within the Earth-Moon system bear a close resemblance to those of Moon-based platforms. Nevertheless, considering the distinct advantages of Moon-based platforms, the lunar surface remains the paramount choice, boasting the highest potential for Earth observation within cislunar space. In summation, this study demonstrates the Earth observation characteristics of the L1 point within the Earth-Moon system, emphasizing the distinctions between this and Moon-based platforms.
... After multi-frame image compression, frame alignment algorithm, and other software processing, a continuous dynamic video is finally formed. As a new method of acquiring image data for Earth observation, Satellite remote sensing video can be applied to large-scale dynamic target change monitoring and its instantaneous characteristic analysis [129]. It reduces the time interval between adjacent image frames by adopting the "image recording" method for a specific area, which not only achieves large-scale coverage but also makes up for the limitation of the re-entry period of traditional satellites. ...
Brain-inspired algorithms have become a new trend in next-generation artificial intelligence. Through research on brain science, the intelligence of remote sensing algorithms can be effectively improved. This paper summarizes and analyzes the essential properties of brain cognise learning and the recent advance of remote sensing interpretation. Firstly, this paper introduces the structural composition and the properties of the brain. Then, five represent brain-inspired algorithms are studied, including multiscale geometry analysis, compressed sensing, attention mechanism, reinforcement learning, and transfer learning. Next, this paper summarizes the data types of remote sensing, the development of typical applications of remote sensing interpretation and the implementations of remote sensing, including datasets, software, and hardware. Finally, the top ten open problems and the future direction of brain-inspired remote sensing interpretation are discussed. This work aims to comprehensively review the brain mechanisms and the development of remote sensing and to motivate future research on brain-inspired remote sensing interpretation.
... In recent years, the concept of Moon-based Earth observation (MEO) has drawn much attentions [13][14][15]. Compared with manmade satellite-based Earth observation systems, MEO holds advantages in providing long-term and consistent measurements, and it can observe the whole Earth disk with a field of view about 2.1° [15]. ...
... Hitherto, MEO systems for the purpose of geoscience applications are still in the phase of concept and system design [15,16]. In literature, relevant studies mainly focused on exploring the spatialtemporal coverage [14,17], developing coordinate transformation framework [18], simulating radiation flux [19], synthetic aperture radar observation [20] and sensor development [21]. ...
As the only natural satellite of the Earth, the Moon provides vital location resources and supportive environment for Earth observations, and the Moon-based Earth observation (MEO) has unparalleled advantages in global climate change and large-scale phenomena. The ocean plays an important role in regulating climate and global water and carbon cycle. With an attempt to explore the feasibility of MEO-based marine environment monitoring, this study aimed to investigate the observing geometry and revisiting frequency of the MEO-based ocean color remote sensing and further to explore its quantitative application potentials. Results showed that: MEO-based ocean color remote sensing, capturing the Earth on an hourly basis, could observe most part of the ocean for over 5 times per day, however, both solar zenith angle and view zenith angle were high at high-latitude regions; atmospheric reflectance accounted for most of sensor-measured signal, especially at high solar and view zenith angle, while surface-reflected glint reflectance was also notable at low solar zenith angle; and the remote sensing reflectance retrieved from MEO-based ocean color remote sensing could be used for Chlorophyll retrieval. In further studies, more efforts should be paid on how to accurately retrieve remote sensing reflectance at high solar and view zenith angle, which would improve the application capability of MEO for polar regions. Overall, this study demonstrated the great potentials of MEO-based ocean color remote sensing, and MEO would be a new observing perspective and long-term consistent data source for marine environment monitoring.
... Moreover, because the lunar surface has a large load capacity, various types of equipment can be placed to collect various types of data. In addition, compared to the current satellite-based platforms, the advantages of Moonbased platform also have been summarized and clarified in existing literature (Huang, 2008;Guo et al., 2018Guo et al., , 2020Ye et al., 2018aYe et al., , 2018bYe et al., , 2019. ...
... Since the utilization of Moon-based platforms to observe the Earth's outgoing radiation is a relatively new research region, the previous work mainly focuses on the feasibility and effectiveness of Moon-based Earth observation (Johnson et al., 2007;Pallé and Goode, 2009), the viewable range and its changes (Ye et al., 2018a(Ye et al., , 2018b, observation geometric conditions , observation methods and error analysis (Guo et al., 2018), and the simulation of the land surface parameters Liao, 2019, 2020). The purpose of this work is to analyze the position difference of irradiance, so as to provide a reference for the parameter design and position selection of the detector. ...
... Huang (2008) pointed out that the changes in the lunar surface temperature are mainly controlled by terrestrial radiation during the lunar nighttime by analyzing the Apollo 15 heat flow experiment data, which provides a good support for the use of Moon-based platform to study Earth radiation. Ye et al. (2018aYe et al. ( , 2018b pointed out that the maximum nadir point's latitudinal and longitudinal difference on the Moon surface is about 0.3°, the maximum viewing angle difference of the Earth is about 0.24°compared with the selenocentric case. In addition, the maximum observation elevation angle difference is about 0.27°caused by different lunar positions and different lunar surface positions also cause changes in the observation duration, energy requirements, and lunar environment of a lunar-based platform. ...
As a platform for longer-term continuous moon-based earth radiation observation (MERO) which includes reflected solar short-wave (SW) radiation and long-wave infrared (LW) radiation, the huge lunar surface space can provide multiple location choices. It is important to analyze the influence of lunar surface position on irradiance which is the aim of the present work based on a radiation heat transfer model. To compare the differences caused by positions, the site of 0°E 0°N was selected as the reference site and a good agreement of the calculation results was verified by the comparison with the NISTAR’s actual detected data. By analyzing the spatial characteristics of the irradiance, the results showed that the irradiance on the lunar surface was of circular distribution and the instrument that was placed in the region of 65°W–65°E and 65°S–65°N could detect the irradiance most effectively. The relative deviation between the reference site and the marginal area (region of > 65°S or 65°N or > 65°W or 65°E) was less than 0.9 mW·m−2 and the small regional differences make a small-scale network conducive to radiometric calibration between instruments. To achieve accurate measurement of the irradiance, the sensitivity design goal of the MERO instrument should be better than 1 mW·m−2 in a future actual design. Because the lunar polar region is the priority region for future exploration, the irradiance at the poles has also been analyzed. The results show that the irradiance changes periodically and exhibits complementary characteristics of time. The variation range of irradiance for short-wave radiation is greater than long-wave radiation and the irradiance of SW reaches the maximum at different times. The MERO at the polar region will provide valuable practical experiment for the follow-up study of the moon-based earth observation in low latitudes.
... The Moon is the only natural satellite of Earth. Many countries have implemented a lunar exploration program with increasing interest in Moon exploration, and various experts have focused on the Moon [25][26][27][28][29][30][31][32]. Compared with artificial satellite platforms, the Moon has several advantages. ...
The variation in the radiation budget at Earth’s top of the atmosphere (TOA) represents the most fundamental metric defining the status of global climate change. The accurate estimation of Earth’s shortwave radiant exitance is of critical importance to study Earth’s radiation budget (ERB) at TOA. Measuring Earth’s outgoing shortwave radiance (OSR) is a key point to estimate Earth’s shortwave radiant exitance. Compared with space-borne satellite systems, Moon-based sensors (MS) could provide large-scale, continuous, and long-term data for Earth radiation observations, bringing a new perspective on ERB. However, the factors affecting the estimation of Earth’s OSR in the lunar direction have not yet been fully explored, for example, anisotropic surface reflection and the effects of clouds and aerosols on radiation budget. In this work, we only focused on the influence of anisotropic surface reflection. To evaluate the extent of this influence, we constructed a model to estimate Earth’s OSR in the lunar direction (EOSRiLD), integrating the variables of anisotropic surface reflection (scene types, solar zenith angles, viewing zenith angles, and relative azimuth angles) and radiant flux in Moon-viewed sunlit regions. Then, we discussed it over three time periods (Earth’s rotation, revolution period, and synodic month cycle) and analyzed the impact of three variables (area of the Moon-viewed sunlit region, scene types, and incident-viewing angular bins) on anisotropic EOSRiLD. Our results indicate that EOSRiLD based on the assumptions of anisotropic and isotropic reflection is different but they all show the same monthly cycle change, which is related to the area of the Moon-viewed sunlit region. At the beginning and end of the lunar month, the differences between anisotropy and isotropy are greatest in each cycle; when it is close to the first half of each cycle, there is a small difference peak. Both anisotropy and isotropy are caused by the relative azimuth angles between the Sun and Moon. In conclusion, even if the Moon-based platform has a wider scope than space-borne satellites, the difference is still large between anisotropy and isotropy. Therefore, we still need to consider the anisotropic surface reflection based on the Moon-based observation.
... A new platform with a higher orbit is expected to overcome these limitations, and the global change observation lunar based SAR was proposed by Guo to explore the possibility of a moon-based platform [13]. Some studies on observation geometry have shown that moon-based SAR has unprecedented spatial-temporal coverage, and the development of this technology will bring great potential for global change observation and geoscience cognition [14], [15], [16]. ...
... These matrices are timedependent and can be obtained using the Earth orientation parameters provided by IERS. For Moon, this transformation is performed by[16] ⎡ ...
Moon-based synthetic aperture radar (SAR) offers unprecedented temporal and spatial coverage. Its repeat-pass interferometry is expected to play a substantial role in earth science because of its large-scale, long-term, near 24.8 h revisit period, and stable earth observation ability. However, it faces a greater challenge when the signal passes through the ionosphere compared with the low Earth orbit (LEO) satellite. In this study, we constructed a total electron content (hereafter referred to as TEC) calculation model for the propagation path of a moon-based SAR signal based on International reference ionosphere model and moon-based SAR interferometry (InSAR) geometry. Subsequently, the ionospheric delay at various carrier frequencies was quantitatively evaluated under different time baseline types. The results show that the interferometric phase space gradient caused by ionospheric can reach ten times that of LEO SAR satellites with superposition of diurnal and seasonal ionospheric variations. In addition, this problem in the observation area with a large incident angle is more severe, which limits the effective swath width of moon-based repeat-pass InSAR. The ionospheric delay effects can be avoided to some extent by selecting the interference combination at nighttime or approaching the solar altitude angle. To highlight the large-scale ground deformation information in most cases and give full play to the long-term and stable observation advantages of the moon-based platform, accurate ionospheric correction or compensation must be considered.
... Within this field, many researchers have compared the Earth observation geometry of sensors installed at different positions on the lunar surface. The majority of the previous studies have indicated that sensors installed on the mid-low latitude region of the Moon will achieve better observation results by avoiding blocking the line of sight [63,64]. The lunar surface is divided into four regions based on different sight conditions between the observed points on Earth and Moon-based platform. ...
Moon-based Earth observations have attracted significant attention across many large-scale phenomena. As the only natural satellite of the Earth, and having a stable lunar surface as well as a particular orbit, Moon-based Earth observations allow the Earth to be viewed as a single point. Furthermore, in contrast with artificial satellites, the varied inclination of Moon-based observations can improve angular samplings of specific locations on Earth. However, the potential for estimating the global outgoing longwave radiation (OLR) from the Earth with such a platform has not yet been fully explored. To evaluate the possibility of calculating OLR using specific Earth observation geometry, we constructed a model to estimate Moon-based OLR measurements and investigated the potential of a Moon-based platform to acquire the necessary data to estimate global mean OLR. The primary method of our study is the discretization of the observational scope into various elements and the consequent integration of the OLR of all elements. Our results indicate that a Moon-based platform is suitable for global sampling related to the calculation of global mean OLR. By separating the geometric and anisotropic factors from the measurement calculations, we ensured that measured values include the effects of the Moon-based Earth observation geometry and the anisotropy of the scenes in the observational scope. Although our results indicate that higher measured values can be achieved if the platform is located near the center of the lunar disk, a maximum difference between locations of approximately 9 × 10−4 W m−2 indicates that the effect of location is too small to remarkably improve observation performance of the platform. In conclusion, our analysis demonstrates that a Moon-based platform has the potential to provide continuous, adequate, and long-term data for estimating global mean OLR.
... In order to accurately describe the motion between the Earth and lunar surface, we first introduce some coordinate systems [10], where the rectangular coordinate systems are Cartesian rectangular coordinate systems satisfying the right hand rule, and the diagram of these systems is shown in Fig. 1. ...
... where represents the inner product operator. Hence the time delay can be obtained by (10), which is shown at the bottom of the page. Therefore, the accurate round-trip slant range can be obtained by substituting (10) into (8). ...
... Tests were successfully conducted in early 2020, and on-orbit deployment is targeted for 2021. [5] . tween the Moon and Earth [9,10] . ...
China is expanding and sharing its capacity for Earth observation by developing sensors, platforms , and launch capabilities in tandem with growing lunar and deep space exploration. China is considering the Moon as a viable Earth observation platform to provide high-quality, planetary-scale data. The platform would produce consistent spatiotemporal data because of its long operational life and the geological stability of the Moon. China is also quickly improving its capabilities in processing and transforming Earth observation data into useful and practical information. Programs such as the Big Earth Data Science Engineering Program (CASEarth) provide opportunities to integrate data and develop "Big Earth Data" platforms to add value to data through analysis and integration. Such programs can offer products and services independently and in collaboration with international partners for data-driven decision support and policy development. With the rapid digital transformation of societies, and consequently increasing demand for big data and associated products, Digital Earth and the Digital Belt and Road Program (DBAR) allow Chinese experts to collaborate with international partners to integrate valuable Earth observation data in regional and global sustainable development.
