Liu Guang

• Professor
• Chinese Academy of Sciences

Equipping sensors on the lunar surface would enable the capture of Earth’s outgoing longwave radiation (OLR) from nearly an entire hemisphere. However, the Earth’s nonsphericity would profoundly impact the observational solid angle, thereby influencing the disk-integrated Earth OLR estimation. This study analyzes the impact of the Earth’s ellipsoid...

Deploying Moon-based sensors at the lunar south polar regions offers unprecedented opportunities for continuous Earth observation. However, previous studies have neglected the combined effects of lunar terrain and latitudinal libration on Earth visibility. This study systematically evaluates the Earth visibility conditions in the lunar south polar...

A Moon-based Earth observation multispectral camera provides a unique perspective for observing large-scale Earth phenomena. This study focuses on the analysis of the field of view (FOV) for such a sensor. Unlike space-borne sensors, the analysis of the FOV for a Moon-based sensor takes into account not only Earth’s maximum apparent diameter as see...

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. T...

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 geometric characteristics of Moon-based Earth observation platforms differ significantly from those of satellite platforms, with geolocation being a key factor that impacts data quality. The geolocation of a Moon-based sensor is influenced by three key factors: lunar ephemeris (lunar position and libration), Earth orientation parameters (EOPs),...

Observation angles are of great importance with respect to Earth observation platforms. The richness of angular combination, i.e., the combination of three observational angles (viewing zenith angle, solar zenith angle, and relative azimuth angle), is an important parameter to illustrate the angle sampling capability of an Earth observation platfor...

Different from existing satellite platforms, a Moon-based platform provides a novel method for monitoring the Earth, owing to its high temporal and spatial scales. In this study, the elevation angle and azimuth angle for Earth features were calculated based on a geometric relationship and through a series of coordinate transformations of both Earth...

The signal propagation of the lunar-based synthetic aperture radar (LBSAR) is affected by perturbations of the lunar orbit, wherein the apsidal precession that exerts a significant impact on the LBSAR imaging performance of the LBSAR deserves special care. Accordingly, the orbital determination used to maintain well-focused quality and high geometr...

The imaging performance of the lunar-based synthetic aperture radar (LBSAR) is susceptible to the orbital perturbation effects. In particular, the perturbations of orbital inclination and right ascension of ascending node (RAAN) could give rise to the temporally varying orbit drift of LBSAR and further lead to Doppler errors in the radio signal. As...

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 thr...

Earth's outgoing radiation (EOR) at the top-of-atmosphere (TOA) is a vital parameter of Earth's energy budget. Moon-based Earth observations as one of the scientific goals of the International Lunar Research Station (ILRS) project could provide long-term, well-calibrated, and disk-integrated EOR data to complement existing platforms. To study the d...

The Earth’s outgoing radiation (EOR) at the top of atmosphere (TOA) is an advantageous goal of Moon-based Earth observations. In this study, we focused on the Earth’s reflected radiation (ERR), which is a component of EOR and has a strong relationship with the Earth–Moon–Sun positions. To determine ERR characteristics, we parameterized the Moon-bas...

Sea ice classification using synthetic aperture radar (SAR) in the wide-swath mode is one method for ice type retrieval. The conventional method of sea ice classification involves single-scale classification, wherein the backscatter and gray level co-occurrence matrix (GLCM) features in a specific resolution are used as classification bases. The cl...

Geological disasters are responsible for the loss of human lives and for significant economic and financial damage every year. Considering that these disasters may occur anywhere—both in remote and/or in highly populated areas—and anytime, continuously monitoring areas known to be more prone to geohazards can help to determine preventive or alert a...

A Moon-based platform can provide efficient observations of large-scale geoscience phenomena on Earth. This study focuses on the global spatio-temporal sampling characteristics of Moon-based Earth observations and quantifies the variations of the spatio-temporal sampling distributions to establish a suitable accumulated sampling period. A theoretic...

To study the Earth’s energy balance and to extend exoplanet research, the Earth’s outward radiative flux and its radiance in the Moon-based view were simulated according to the Earth–Sun–Moon geometry model, with the help of ERA5. A framework was developed to identify the angular distribution model (ADM) of Earth’s surface and its scene types, acco...

The outgoing longwave radiation (OLR) at the top of the atmosphere is a key component of Earth’s radiation budget. Moon-based OLR observations take Earth as a single point, and provide an alternative to near-Earth orbital measurements. However, in the sensitivity design of a sensor, the effects of adopted Earth’s shape on the design of the sensitiv...

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 vari...

Due to the almost hemispheric observational scope of the Moon-based Earth observations, the effects of sampling time interval on the image offsets of the observed points are fundamentally different from the cases of traditional satellite-based platforms. Sampling time intervals will affect the offsets in the full-disc image, while the magnitude of...

Synthetic aperture radar interferometry (InSAR) is the technique capable of monitoring active landslide in all-weather conditions and in a near real-time. In this study, ALOS-2 (L-band) and Sentinel-1 (C-Band) images were used to map potential areas prone to the occurrence of large-scale landslide disasters. Differential InSAR (D-InSAR) and multi-t...

The ice avalanche disaster caused by glacier movements threatens the safety of the downstream area of the glacier. The monitoring method based on SAR data allows the detection of glaciers’ movement at all weather conditions. In addition, SAR-based techniques are capable of analyzing the phenomena in large area and with long time span which has impo...

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...

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 observati...

Moon-based earth observation is an exploratory topic, expected to open up a new perspective on earth observation and has attracted considerable attention in recent years. Sea ice covers large areas of polar regions and plays a crucial role in the earth system. In this study, the moon-based observation coverage of sea ice is investigated in terms of...

Glaciers in the eastern Pamir have reportedly been gaining mass during recent decades, even though glaciers in most other regions in High Mountain Asia have been in recession. Questions still remain about whether the trend is strengthening or weakening, and how far the positive balances extend into the eastern Pamir. To address these gaps, we use t...

Using the Moon as an Earth observation platform for remote sensing offers the benefits of a high orbital altitude and vast surface area, which could provide continuous Earth observation capabilities over great temporal and spatial scales. Over the course of China's follow-up lunar missions in the next three Five-year plans, the Earth observation in...

The Karakoram has had an overall slight positive glacier mass balance since the end of 20th century, which is anomalous given that most other regions in High Mountain Asia have had negative changes. A large number of advancing, retreating, and surging glaciers are heterogeneously mixed in the Karakoram increasing the difficulties and inaccuracies t...

The effects of temporal sampling interval on the Moon-based Earth observation geometry is analyzed in this study based on three observation angles, namely viewing zenith angle, solar zenith angle, and relative azimuth angle. According to the definitions of these three angles, the calculation method for these angles and their variations between adja...

Because of their scientific and social significance, large-scale geoscientific phenomena are attracting more and more attention. However, many existing Earth observation systems lack the ability to conduct long-term continuous observations on regional to global scales because of limitations on spatial and temporal coverage and the existence of syst...

The spatiotemporal coverage of a Moon-based synthetic aperture radar (SAR) is analyzed based on the imaging geometry, upon which the spatial coverage and image formulation rely. The distance from the Earth to the Moon-based SAR and bounds of the grazing and azimuthal angles jointly determine the coverage area on the Earth's surface. Meanwhile, the...

A surge-type glacier is a special and dangerous type of glacier, which can advance quickly in a short-time with cycles. Glaciers in the Yangtze River headwater are generally acknowledged to be in a stable state. However, not all of those glaciers are stable. In this paper, five glaciers from the Yangtze River headwater glacier were selected as the...

The Antarctic and Arctic have always been critical areas of earth science research and are sensitive to global climate change. Global climate change exhibits diversity characteristics on both temporal and spatial scales. Since the Moon-based earth observation platform could provide large-scale, multi-angle, and long-term measurements complementary...

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...

The Moon provides us with a long-term, stable, and unique place for Earth observation. Space agencies of various countries, including the United States, China, and Italy, have made the realization of Moon-based Earth observation an objective of their lunar missions. To date, although some conceptual studies have been presented, an accurate geometri...

Global change affected by multiple factors, the consequences of which continue to be far-reaching, has the characteristics of large spatial scale and long-time scale. The demand for Earth observation technology has been increasing for large-scale simultaneous observations and stable global observation over the long-term. A Moon-based observation pl...

Aberrations exist in any moving system that transmits or receives electromagnetic waves. In orbital imaging, these aberrations were ignored before the development of the high-resolution Earth observation system and the high-orbit Earth observation system. In this paper, a two-step model is presented to evaluate the difference between the hypothetic...

As a new potential platform for Earth observation, the Moon which is a natural satellite unique to the Earth has been paid more and more attention for its consistent and continuous observation capability of global-scale and macroscopic geoscience phenomena on Earth. Because of the effect of Earth curvature and the Earth–Moon geometric relationship,...

There are increasing concerns about the Arctic region and the Antarctic region, which are known as indicators of the global change. To conduct research on the global change issue, especially for the two-polar regions of the Earth, the long-term continuous Earth observations are required. However, the existing Earth observation systems lack the abil...

Changes in sea water salinity are closely related to the ocean environment and global climate change. Both the Soil Moisture and Ocean Salinity (SMOS) satellite launched by ESA in November 2009 and the Aquarius satellite launched by NASA in 2011 were designed to measure sea surface salinity. This chapter discusses China’s scientific satellites (ope...

Atmospheric aerosol plays a very important role in global change. It produces direct radiative forcing by absorbing and scattering shortwave radiation; it also affects cloud microphysics and therefore hydrological processes, producing indirect radiative forcing. Atmospheric aerosol also has an important impact on air quality and ecological environm...

A pattern of both competition and cooperation has been formed in the fields of space and Earth observation today. Major space powers and developmental organizations have launched new strategies and programs revealing the development of future space and Earth observation technology. Most nations desire a foothold in space and Earth observation, wher...

The USA is the world’s most powerful country in terms of aerospace technology. Since 1960 when it launched its first Earth observation satellite, TIROS, which was intended for television infrared observation, the country has made a great progress in Earth observation technology. The National Aeronautics and Space Administration (NASA) planned to us...

Urbanization is an important process of human civilization (Gu et al. 2012). The city system plays an important role in global social, economic, cultural, political, and environmental systems, but it also brings along such environmental problems as air pollution, the heat island effect, increased overland runoff, water quality deterioration, and la...

In recent years, scholars have proposed studying the Moon as a platform for Earth observation. This includes research on the observation geometry and related parameters, and simulating the typical applications of Moon-based observation.

Integration and coordination of Earth observation activities have been gradually strengthened with the rapid development of Earth observation technologies. Global data support is necessary for observing and studying the atmosphere, land, ocean, and other elements of the Earth system, and no single country or institution can independently pursue the...

As previously mentioned, Earth observation technology enables us to more profoundly understand changes in Earth’s physical, chemical, and biological systems. In the context where all countries are faced with threatening problems such as environmental pollution, energy shortages, and natural disasters, global-scale, Earth observation systems (EOS) h...

In order to understand Earth’s global change, humanity should not only study the interaction between Earth’s atmosphere, hydrosphere, biosphere, and lithosphere, but should also take other planets within the solar system into consideration. Comparative research of other planets helps deepen our understanding of global environmental change and the g...

As the main player in the terrestrial biosphere, forests are of great significance in keeping the global carbon balance. Forests are also the biggest carbon sink in terrestrial ecosystems, accounting for at least 86% of the global vegetation carbon pool.

Glacial change is an important part of global change. Its evolutionary process directly reflects global climate change, and its data features high resolutions, a large amount of information, and high fidelity.

European countries have the world’s most advanced Earth observation satellites, and the European Space Agency (ESA) is the main promoter of Earth observation technology and satellite missions. The European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) is responsible for the development, launch, and maintenance of Europea...

Earth has undergone 4.6 billion years of natural evolution, during which large-scale dynamic changes created the current living environment of human beings. The monitoring and research of macroscopic global change are not only significant from a scientific perspective, but are also important to guide the adjustment of human activities.

Human activities have produced approximately 200 billion tons of carbon over the past fifty to sixty years, and such carbon was mainly emitted into the atmosphere in the form of CO2. Now, the observed rises in global mean temperature, sea surface temperature and average sea level, and wide-ranging ice melting show a definite trend in global warming...

Remote sensing is a scientific technology that uses sensors carried by spacecraft, aircraft, and various terrestrial platforms to observe Earth’s environment and human activities. Artificial satellites that carry sensors to capture images of Earth’s surface are referred to as Earth observation satellites. Satellites can successively observe the who...

China successfully launched its first meteorological satellite (FY-1A) in 1988. The country, driven by national needs and scientific progress, has gradually established a comprehensive Earth observation satellite system through 25 years of development (Fig. 6.1). The system comprises meteorological satellites, ocean satellites, resource satellites,...

Since the first artificial satellite was launched in 1957, Earth observation systems based on ground observation, aerial remote sensing, and satellite remote sensing have provided humankind with powerful Earth observation capabilities.

Moon-based platform is a potential platform that can realize the observations of large-scale geoscience phenomenon. Unlike existing earth observation platforms, the moon-based platform is equipped on a natural celestial body. Its position is calculated by the lunar position and libration derived from the planetary ephemeris. However, limited to the...

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 D...

Geologically, La Paz City is located in an unstable area. During the history of La Paz city, many landslides have destroyed houses and valuable infrastructures. In the last decades, time series Interferometric Synthetic Aperture Radar (InSAR) technologies have demonstrated a great capacity for detecting slow ground displacement, achieving an accura...

This study investigates the temporal sampling error on the Earth’s outgoing radiation, with a potential Earth observation platform, the Moon-based platform. To simulate the Earth’s outgoing radiation viewed from a Moon-based platform, we used the datasets of the NASA’s Goddard Earth Observing System Version 5 (GEOS-5) systems as the truth. The anal...

The offset tracking technique based on synthetic aperture radar (SAR) image intensity information can estimate glacier displacement even when glacier velocities are high and the time interval between images is long, allowing for the broad use of this technique in glacier velocity monitoring. Terrestrial laser scanners, a non-contact measuring syste...

Landslide is a hazard that threaten the people who lives in the mountain area, it comes active especially rainy seasons and causes a large number of casualties every year. The movement of the slope is an indicator of activity of the landslide, it is helpful to capture the precursor of the activity, the monitoring of the movement of the slope is ver...

Glaciers in the Pamir Mountains are generally acknowledged to be in a stable state and show the least glacial retreat in high-mountain Asia; however, they are also some of the most dynamic glaciers in the region and their behaviour has been spatially variable in recent decades. Few data exist for these glaciers, in particular relating to how they a...

Effective methods of sea ice classification are crucial to regional ice type mapping using spaceborne synthetic aperture radar (SAR), especially in ScanSAR mode. However, in TerraSAR-X ScanSAR images of ocean scenes, the scalloping and interscan banding (ISB) artifacts are usually visible. Though these two artifacts could be reduced to a certain de...

Global change involves complex and far-reaching variations in the Earth’s systems, and satellite observations have been widely used in global change studies. Over the past five decades, Earth observation has developed into a comprehensive system that can conduct dynamic monitoring of the land, the oceans and the atmosphere at the local, regional an...

Mountain glacier is one of the extremely sensitive indicators for climate change, and its surface motion distribution and corresponding variation are valuable information for understanding ice mass exchange and glacier dynamics. This paper presents the long-term ice velocity distributions of Inylchek Glacier in the Tianshan region by pixel-tracking...

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-bas...

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 ori...

Glaciers in the Pamir Mountains are generally acknowledged to be in a stable state and show the least glacial retreat in High Mountain Asia; however, they are also some of the most dynamic glaciers in the region and their behaviour has been spatially variable in recent decades. Few data exist for these glaciers, in particular relating to how they a...

Sustainability is the current theme of global development, and for China, it is not only an opportunity but also a challenge. In 2016, the Paris Agreement on climate change was adopted, addressing the need to limit the rise of global temperatures. The United Nations (UN) has set Sustainable Development Goals (SDGs) to transform our world in terms o...

Gravity waves (GWs) have been intensively studied over recent decades because of their dominant role in the dynamics of the mesosphere and lower thermosphere (MLT). The momentum deposition caused by breaking GWs determines the basic structure and drives the large-scale circulation in the MLT. Satellite observations provide a way to qualify the prop...

COSMO-SkyMed is a constellation of four X-band high-resolution radar satellites with a minimum revisit period of 12 hours. These satellites can obtain ascending and descending synthetic aperture radar (SAR) images with very similar periods for use in the three-dimensional (3D) inversion of glacier velocities. In this paper, based on ascending and d...

Earth System Science is a discipline that performs holistic and comprehensive research on various components of the Earth. One of a key issue for the Earth monitoring and observation is to enhance the observation duration, the time intervals during which the Earth surface features can be observed by sensors. In this work, we propose to utilise the...

It is more difficult to retrieve land surface temperature (LST) from passive microwave remote sensing data than from thermal remote sensing data, because the emissivities in the passive microwave band can change more easily than those in the thermal infrared band. Thus, it is very difficult to build a stable relationship. Passive microwave band emi...

Gravity waves (GWs) have been intensively studied over recent decades because of their dominant role in the dynamics of the mesosphere and lower thermosphere (MLT). The momentum deposition caused by breaking GWs determines the basic structure and drives the large-scale circulation in the MLT. Satellite observations provide a way to qualify the prop...

Gravity waves (GWs) play an important role in the dynamics of the mesosphere and lower thermosphere (MLT). Therefore, global observations of GWs in the MLT region are of particular interest. The small scales of GWs, however, pose a major problem for the observation of GWs from space. We propose a new observation strategy for GWs in the mesopause re...

Land use change is affected by many driving factors such as the economy, population, and government policy. This study investigated the relationship between government policy and land use change to develop an understanding applicable to the formulation of strategies for sustainable land use. The Lijiang River Basin in the Guangxi Zhuang Autonomous...

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...

Fanjiaping landslide, located on the south bank of the Yangtze River in Zigui County of Hubei Province, is one of the large-scale rocky landslides along the main stream in the Three Gorges Reservoir area. The working method and technological system of high resolution InSAR are briefly introduced in this paper. Furthermore, based on 22 TerraSAR-X im...

This work made an improvement upon and a further evaluation of previous work for estimating water vapor content from near-infrared around 1 μm from MODIS data. The accuracy of RM-NN is determined by the complicated relationship of the geophysical parameters. An advanced scheme is proposed for building different training databases for different seas...

Although Earth’s surface parameters obtained from satellite data have become more and more precise, it is still difficult to guarantee temporal consistency and spatial continuity for large-scale geoscience phenomena. Developing new Earth observation platforms is a feasible way to improve the consistency and continuity of such data. As the planet’s...