Trajectory Determination of Chang’E-5 during Landing and Ascending

Chang’E-5 (CE-5) is China’s first lunar sample return mission. This paper focuses on the trajectory determination of the CE-5 lander and ascender during the landing and ascending phases, and the positioning of the CE-5 lander on the Moon. Based on the kinematic statistical orbit determination method using B-spline and polynomial functions, the descent and ascent trajectories of the lander and ascender are determined by using ground-based radiometric ranging, Doppler and interferometry data. The results show that a B-spline function is suitable for a trajectory with complex maneuvers. For a smooth trajectory, B-spline and polynomial functions can reach almost the same solutions. The positioning of the CE-5 lander on the Moon is also investigated here. Using the kinematic statistical positioning method, the landing site of the lander is 43.0590°N, 51.9208°W with an elevation of −2480.26 m, which is less than 200 m different from the LRO (Lunar Reconnaissance Orbiter) image data.

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A global rockfall map of the Moon powered by AI and Big Data

10.5194/egusphere-egu2020-10003 ◽

2020 ◽

Author(s):

Valentin Bickel ◽

Jordan Aaron ◽

Andrea Manconi ◽

Simon Loew ◽

Urs Mall

Keyword(s):

Spatial Distribution ◽

High Resolution ◽

Lunar Surface ◽

Image Data ◽

Landing Site ◽

Planetary Science ◽

The Moon ◽

Lunar Orbiter ◽

Narrow Angle ◽

Lunar Reconnaissance Orbiter

Under certain conditions, meter to house-sized boulders fall, jump, and roll from topographic highs to topographic lows, a landslide type termed rockfall. On the Moon, these features have first been observed in Lunar Orbiter photographs taken during the pre-Apollo era. Understanding the drivers of lunar rockfall can provide unique information about the seismicity and erosional state of the lunar surface, however this requires high resolution mapping of the spatial distribution and size of these features. Currently, it is believed that lunar rockfalls are driven by moonquakes, impact-induced shaking, and thermal fatigue. Since the Lunar Orbiter and Apollo programs, NASA&#8217;s Lunar Reconnaissance Orbiter Narrow Angle Camera (NAC) returned more than 2 million high-resolution (NAC) images from the lunar surface. As the manual extraction of rockfall size and location from image data is time intensive, the vast majority of NAC images have not yet been analyzed, and the distribution and number of rockfalls on the Moon remains unknown. Demonstrating the potential of AI for planetary science applications, we deployed a Convolutional Neural Network in combination with Google Cloud&#8217;s advanced computing capabilities to scan through the entire NAC image archive. We identified 136,610 rockfalls between 85&#176;N and 85&#176;S and created the first global, consistent rockfall map of the Moon. This map enabled us to analyze the spatial distribution and density of rockfalls across lunar terranes and geomorphic regions, as well as across the near- and farside, and the northern and southern hemisphere. The derived global rockfall map might also allow for the identification and localization of recent seismic activity on or underneath the surface of the Moon and could inform landing site selection for future geophysical surface payloads of Artemis, CLPS, or other missions. The used CNN will soon be available as a tool on NASA JPL&#8217;s Moon Trek platform that is part of NASA&#8217;s Solar System Treks (trek.nasa.gov/moon/).

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LROC candidate images with solar glints off Lunar Laser Retroreflectors: A dedicated tool of NASA's Moon Trek

10.5194/epsc2020-614 ◽

2020 ◽

Author(s):

Costanza Rossi ◽

Natalie Gallegos ◽

Luciana Filomena ◽

Shan Malhotra ◽

Emily Law ◽

...

Keyword(s):

Coordinate System ◽

Image Data ◽

The Moon ◽

Lunar Laser Ranging ◽

Time Intervals ◽

Morphological Pattern ◽

Ground Station ◽

Lunar Laser ◽

Lunar Reconnaissance Orbiter ◽

Phase Angles

The Lunar Laser Ranging (LLR) investigations have provided time high-precision measurements of geodesy, dynamics and distance of the Earth-Moon system, and inferences about lunar interior and gravitational physics. LLR studies are supported by a total of five passive Laser Retro-Reflectors (LRR) placed on the Moon surface by the past missions Apollo-11, -14, -15 and Luna-17 and -21. The detection of their positions is decisive to improve the measurement accuracy and the data from alternative instrumentations contributed to their analysis. The Lunar Reconnaissance Orbiter Camera (LROC) operated by using the Standardized Lunar Coordinate System as reference system has acquired images of the Moon surface that represent data applicable to LLR planning and research. Several LROC images present nominal lighting conditions and solar glints reflected off of an LRR. Glints represent specular reflections of light that define higher-precision measurement of LRR position. In this way, their detection plays an important role in LRR analysis. The identification of candidate images with solar glints through time allows researchers to record these measurements. NASA and INFN-LNF (National Lab of Frascati) have collaboratively developed an LLR tool to support glint identification. The tool can be accessed using the Moon Trek (https://trek.nasa.gov/moon) which is one of the web based interactive visualization and analysis portals provided by the NASA&#8217;s Solar System Trek (https://trek.nasa.gov) project. The tool facilitates current ranging studies as well as planning of future missions that involve ranging activities such as future retroreflector deployments. Glint identification has been performed by using the LLR tool that allows us to investigate the image data, and to compute geometric calculations and LLR analyses. The tool with SPICE computations is provided to search for nominal conditions to catch a solar glint off of a retroreflector, to search for time intervals in which a reflector can be seen from a ground station on Earth, and to search in PDS database for images with these conditions. Moon Trek&#8217;s LLR tool allows us to find time intervals when spacecraft positioning was able to catch a solar glint reflected off of a retroreflector by setting the maximum incidence and phase angles. This analysis is accompanied by the search for LROC images available in Planetary Data System (PDS) that have solar glint off the LRR. Using the Moon Trek, it is possible to identify LROC images with solar glint off the LRR and to recognize optimal LROC candidates. This research allows us to identify good examples of LROC images that present solar glints. More than six candidate images over a period of 10 years of LROC data were recognized. In this contribution, we present the recognized LROC candidates and we show their detection in the image data, by avoiding the bias of the surface high albedo and the morphological pattern that can interfere with the analysis. The identification of solar glints off LRR will allow us to find previous observation that might be incorrect and to measure the LRR position in the Standardized Lunar Coordinate System of LROC images. These measures will be then compared with the ephemeris calculations obtained from LLR data.

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Topographic and Geomorphological Mapping and Analysis of the Chang'E-4 Landing Site on the Far Side of the Moon

Photogrammetric Engineering & Remote Sensing ◽

10.14358/pers.86.4.247 ◽

2020 ◽

Vol 86 (4) ◽

pp. 247-258 ◽

Cited By ~ 1

Author(s):

Bo Wu ◽

Fei Li ◽

Han Hu ◽

Yang Zhao ◽

Yiran Wang ◽

...

Keyword(s):

Landing Site ◽

Joint Analysis ◽

The Sun ◽

The Moon ◽

Soft Landing ◽

Geomorphological Mapping ◽

Von Karman ◽

Lunar Reconnaissance Orbiter ◽

Integrated Processing ◽

Von Kármán

The Chinese lunar probe Chang'E-4 successfully landed in the Von Kármán crater on the far side of the Moon. This paper presents the topographic and geomorphological mapping and their joint analysis for selecting the Chang'E-4 landing site in the Von Kármán crater. A digital topographic model (DTM) of the Von Kármán crater, with a spatial resolution of 30 m, was generated through the integrated processing of Chang'E-2 images (7 m/pixel) and Lunar Reconnaissance Orbiter (LRO) Laser Altimeter (LOLA) data. Slope maps were derived from the DTM. Terrain occlusions to both the Sun and the relay satellite were studied. Craters with diameters ≥ 70 m were detected to generate a crater density map. Rocks with diameters ≥ 2 m were also extracted to generate a rock abundance map using an LRO narrow angle camera (NAC) image mosaic. The joint topographic and geomorphological analysis identified three subregions for landing. One of them, recommended as the highest-priority landing site, was the one in which Chang'E-4 eventually landed. After the successful landing of Chang'E-4, we immediately determined the precise location of the lander by the integrated processing of orbiter, descent and ground images. We also conducted a detailed analysis around the landing location. The results revealed that the Chang'E-4 lander has excellent visibility to the Sun and relay satellite; the lander is on a slope of about 4.5° towards the southwest, and the rock abundance around the landing location is almost 0. The developed methods and results can benefit future soft-landing missions to the Moon and other celestial bodies.

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Detection of Small Impact Craters via Semantic Segmenting Lunar Point Clouds Using Deep Learning Network

Remote Sensing ◽

10.3390/rs13091826 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1826

Author(s):

Yifan Hu ◽

Jun Xiao ◽

Lupeng Liu ◽

Long Zhang ◽

Ying Wang

Keyword(s):

Image Data ◽

Landing Site ◽

Semantic Segmentation ◽

Point Clouds ◽

Impact Craters ◽

Detection Accuracy ◽

The Moon ◽

Small Impact ◽

Crater Detection ◽

Deep Learning Network

Impact craters refer to the most salient features on the moon surface. They are of huge significance for analyzing the moon topography, selecting the lunar landing site and other lunar exploration missions, etc. However, existing methods of impact crater detection have been largely implemented on the optical image data, thereby causing them to be sensitive to the sunlight. Thus, these methods can easily achieve unsatisfactory detection results. In this study, an original two-stage small crater detection method is proposed, which is sufficiently effective in addressing the sunlight effects. At the first stage of the proposed method, a semantic segmentation is conducted to detect small impact craters by fully exploiting the elevation information in the digital elevation map (DEM) data. Subsequently, at the second stage, the detection accuracy is improved under the special post-processing. As opposed to other methods based on DEM images, the proposed method, respectively, increases the new crusher percentage, recall and crusher level F1 by 4.89%, 5.42% and 0.67%.

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ELEMENTAL AND TOPOGRAPHIC MAPPING OF LAVA FLOWSTRUCTURES IN MARE SERENITATIS ON THE MOON

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-archives-xlii-3-w1-163-2017 ◽

2017 ◽

Vol XLII-3/W1 ◽

pp. 163-170 ◽

Cited By ~ 2

Author(s):

C. Wöhler ◽

A. Grumpe ◽

D. Rommel ◽

M. Bhatt ◽

U. Mall

Keyword(s):

Lava Flow ◽

Flow Structure ◽

Hyperspectral Image ◽

Image Data ◽

Elemental Abundance ◽

Lava Flows ◽

Stereo Image ◽

The Moon ◽

Lunar Reconnaissance Orbiter ◽

Mare Serenitatis

The detection of lunar lava flows based on local morphology highly depends on the available images. The thickness of lava flows, however, has been studied by many researchers and lunar lava flows are shown to be as thick as 200&thinsp;m. Lunar lava flows are supposed to be concentrated on the northwestern lunar nearside. In this study we present elemental abundance maps, a petrological map and a digital terrain model (DTM) of a lava flow structure in northern Mare Serenitatis at (18.0&deg;&thinsp;E, 32.4&deg;&thinsp;N) and two possible volcanic vents at (11.2&deg;&thinsp;E, 24.6&deg;&thinsp;N) and (13.5&deg;&thinsp;E, 37.5&deg;&thinsp;N), respectively. Our abundance maps of the refractory elements Ca, Mg and our petrological map were obtained based on hyperspectral image data of the Moon Mineralogy Mapper (M3) instrument. Our DTM was constructed using GLD100 data in combination with a shape from shading based method to M3 and Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) image data. The obtained NAC-based DEM has a very high effective resolution of about 1&ndash;2&thinsp;m which comes close to the resolution of the utilized NAC images without requiring intricate processing of NAC stereo image pairs. As revealed by our elemental maps and DEM, the examined lava flow structure occurs on a boundary between basalts consisting of low-Ca/high-Mg pyroxene and high-Ca/low-Mg pyroxene, respectively. The total thickness of the lava flow is about 100&thinsp;m, which is a relatively large value, but according to our DEM the lava flow may also be composed of two or more layers.

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Information and estimation in image processing

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100125142 ◽

1987 ◽

Vol 45 ◽

pp. 14-17

Author(s):

B. Roy Frieden

Keyword(s):

Image Processing ◽

Optical System ◽

Large Amplitude ◽

Communication Theory ◽

Image Data ◽

Direct Approach ◽

Ill Posed

Despite the skill and determination of electro-optical system designers, the images acquired using their best designs often suffer from blur and noise. The aim of an “image enhancer” such as myself is to improve these poor images, usually by digital means, such that they better resemble the true, “optical object,” input to the system. This problem is notoriously “ill-posed,” i.e. any direct approach at inversion of the image data suffers strongly from the presence of even a small amount of noise in the data. In fact, the fluctuations engendered in neighboring output values tend to be strongly negative-correlated, so that the output spatially oscillates up and down, with large amplitude, about the true object. What can be done about this situation? As we shall see, various concepts taken from statistical communication theory have proven to be of real use in attacking this problem. We offer below a brief summary of these concepts.

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Rock Location and Property Analysis of Lunar Regolith at Chang’E-4 Landing Site Based on Local Correlation and Semblance Analysis

Remote Sensing ◽

10.3390/rs13010048 ◽

2020 ◽

Vol 13 (1) ◽

pp. 48

Author(s):

Hanjie Song ◽

Chao Li ◽

Jinhai Zhang ◽

Xing Wu ◽

Yang Liu ◽

...

Keyword(s):

Electromagnetic Waves ◽

Lunar Regolith ◽

Landing Site ◽

Rock Properties ◽

The Moon ◽

Local Correlation ◽

Near Surface ◽

Property Analysis ◽

Stratigraphic Division ◽

Formation And Evolution

The Lunar Penetrating Radar (LPR) onboard the Yutu-2 rover from China’s Chang’E-4 (CE-4) mission is used to probe the subsurface structure and the near-surface stratigraphic structure of the lunar regolith on the farside of the Moon. Structural analysis of regolith could provide abundant information on the formation and evolution of the Moon, in which the rock location and property analysis are the key procedures during the interpretation of LPR data. The subsurface velocity of electromagnetic waves is a vital parameter for stratigraphic division, rock location estimates, and calculating the rock properties in the interpretation of LPR data. In this paper, we propose a procedure that combines the regolith rock extraction technique based on local correlation between the two sets of LPR high-frequency channel data and the common offset semblance analysis to determine the velocity from LPR diffraction hyperbola. We consider the heterogeneity of the regolith and derive the relative permittivity distribution based on the rock extraction and semblance analysis. The numerical simulation results show that the procedure is able to obtain the high-precision position and properties of the rock. Furthermore, we apply this procedure to CE-4 LPR data and obtain preferable estimations of the rock locations and the properties of the lunar subsurface regolith.

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Automated Determination of the Position of Ships by Satellites

Journal of Navigation ◽

10.1017/s0373463300024528 ◽

1967 ◽

Vol 20 (03) ◽

pp. 281-285

Author(s):

H. C. Freiesleben

Keyword(s):

Celestial Body ◽

World Wide ◽

Artificial Satellites ◽

Radio Waves ◽

The Moon ◽

Position Determination ◽

The Earth ◽

Navigational Aids ◽

Automated Determination

It has recently been suggested that 24-hour satellites might be used as navigational aids. To what category of position determination aids should these be assigned ? Is a satellite of this kind as it were a landmark, because, at least in theory, it remains fixed over the same point on the Earth's surface, in which case it should be classified under land-based navigation aids ? Is it a celestial body, although only one tenth as far from the Earth as the Moon ? If so, it is an astronomical navigation aid. Or is it a radio aid ? After all, its use for position determination depends on radio waves. In this paper I shall favour this last view. For automation is most feasible when an object of observation can be manipulated. This is easiest with radio aids, but it is, of course, impossible with natural stars.At present artificial satellites have the advantage over all other radio aids of world-wide coverage.

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Astronomy at the service of the Islamic society

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311002778 ◽

2009 ◽

Vol 5 (S260) ◽

pp. 514-521

Author(s):

Ilias M. Fernini

Keyword(s):

Proper Time ◽

Astronomical Observatory ◽

The Sun ◽

The Moon ◽

Scientific Institutions ◽

Mathematical Astronomy ◽

Islamic Empire ◽

New Moon ◽

Islamic Society

AbstractThe Islamic society has great ties to astronomy. Its main religious customs (start of the Islamic month, direction of prayer, and the five daily prayers) are all related to two main celestial objects: the Sun and the Moon. First, the start of any Islamic month is related to the actual seeing of the young crescent after the new Moon. Second, the direction of prayer, i.e., praying towards Mecca, is related to the determination of the zenith point in Mecca. Third, the proper time for the five daily prayers is related to the motion of the Sun. Everyone in the society is directly concerned by these customs. This is to say that the major impetus for the growth of Islamic astronomy came from these three main religious observances which presented an assortment of problems in mathematical astronomy. To observe these three customs, a new set of astronomical observations were needed and this helped the development of the Islamic observatory. There is a claim that it was first in Islam that the astronomical observatory came into real existence. The Islamic observatory was a product of needs and values interwoven into the Islamic society and culture. It is also considered as a true representative and an integral par of the Islamic civilisation. Since astronomy interested not only men of science, but also the rulers of the Islamic empire, several observatories have flourished. The observatories of Baghdad, Cairo, Córdoba, Toledo, Maragha, Samarqand and Istanbul acquired a worldwide reputation throughout the centuries. This paper will discuss the two most important observatories (Maragha and Samarqand) in terms of their instruments and discoveries that contributed to the establishment of these scientific institutions.

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Shape of the Moon from the Orbiter Determination of its Gravitational Field

Nature ◽

10.1038/212271a0 ◽

1966 ◽

Vol 212 (5059) ◽

pp. 271-271 ◽

Cited By ~ 2

Author(s):

C. L. GOUDAS ◽

Z. KOPAL ◽

Z. KOPAL

Keyword(s):

Gravitational Field ◽

The Moon

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