scholarly journals The Shape of the Moon

1972 ◽  
Vol 47 ◽  
pp. 22-31 ◽  
Author(s):  
S. K. Runcorn ◽  
S. Hofmann
Keyword(s):  
Lunar Surface ◽  
Major Axis ◽  
Great Depth ◽  
The Moon ◽  
Method Of Least Squares ◽  
Global Shape ◽  
The Earth ◽  
Intrinsic Scatter ◽  
Simple Statistical Analysis

The determination of the heights of points on the lunar surface by Earth based astronomy using the geometrical librations, although individually of low accuracy, still provides our best method of obtaining the global shape of the Moon. The intrinsic scatter of the results arises from the effects of ‘seeing’ and simple statistical analysis is required to derive valid conclusions about the shape. Baldwin's method of fitting ellipsoidal surfaces to the points on the maria and uplands, separately by the method of least squares proves to be a valuable tool.Analyses of the ACIC points and of the Pic du Midi studies of G. A. Mills show that good first descriptions of the global shape of the Moon for both the maria and uplands are triaxial ellipsoids with their long axes within 10° of the Earth direction, the major axis of the maria being about 1.3 km smaller than that of the uplands. Of particular significance is that the ellipticity of these surfaces is about 2½ times greater than the dynamical ellipticity; thus the non-hydrostatic figure of the Moon is not simply the result of distortion from a uniform Moon during its early history. The angular variation in density within the Moon cannot be simply a phenomena within the crust but must extend to a great depth. Convection could provide an explanation.The departures of the lunar surface from the idealised ellipsoids are also of interest. The circular maria are systematically depressed relative to the maria ellipsoid: can the mascons have adjusted isostatically since their formation? Systematic differences in height between the western and eastern southern uplands are also noted.

Evidence from the surface configuration of the Moon on its dynamical evolution

1967 ◽  
Vol 296 (1446) ◽  
pp. 298-303
Keyword(s):  
Lunar Surface ◽  
High Velocity ◽  
Dynamical Evolution ◽  
Great Majority ◽  
Major Axis ◽  
The Moon ◽  
Moon System ◽  
The Past ◽  
The Earth ◽  
High Velocity Impacts

Examination of the Moon through large telescopes reveals a multitude of fine detail down to a scale of 1 km or less. The most prominent feature of the lunar surface is the abundance of circular craters. Many investigators agree that a great majority of these craters have been caused by explosions associated with high velocity impacts. It is further generally assumed that the majority of these high velocity impacts took place during the earliest stages of development of the present Earth-Moon system. The morphology of the Moon surface appears in dynamical considerations in the following way. We know from the work of G. H. Darwin that the Moon has been steadily retreating from the Earth. Dynamical considerations suggest that the period of rotation of the Moon on the average equals its period of revolution about the Earth. Thus when the Moon approaches the Earth, its rotation would be accelerated. Since the Moon, like the Earth, approximates to a fluid body, we should expect that a figure of the Moon would have changed in response to its changing rate of rotation. If the craters formed at a time at which the Moon’s figure was markedly different from the present, then initially circular craters would be deformed and any initially circular depression would tend to change into an elliptically shaped depression, with the major axis of the ellipse along the local meridian. Study of the observed distortions of the craters can give evidence as to the past shape of the Moon, provided the craters formed at a time when the Moon possessed a different surface ellipticity. I should like to examine the limitations the present surface structure places on the past dynamical history of the Moon. I will first review briefly calculations bearing on the dynamical evolution of the Earth-Moon system and the implications these calculations have on the past shape of the lunar surface.

scholarly journals Que pourra-t-on deduire des mesures de distance terre-lune par laser?

1974 ◽  
Vol 61 ◽  
pp. 269-274
Author(s):  
J. Kovalevsky
Keyword(s):  
Major Axis ◽  
Radio Interferometry ◽  
The Moon ◽  
Semi Major Axis ◽  
Lunar Laser Ranging ◽  
The Earth ◽  
Lunar Laser ◽  
Observational Errors ◽  
External Check

Although several lunar laser ranging stations exist, only one is now fully operational: the McDonald station with internal observational errors of less than 15 cm. The interpretation of the data involves a great number of parameters relative to the Earth and the Moon which are listed.The lunar laser is particularly fit for those parameters that pertain to the Moon, and with future lasers accurate to 2 or 3 cm, it may be expected that this accuracy will be projected into these parameters. The probable determination of the semi-major axis to 1 cm accuracy for a few months mean would imply a new means of determining the non conservative part of the motion of the Moon. A similar precision is to be expected for the rotation of the Moon. The situation for the Earth parameters (Earth rotation and polar motion) is not so good, because of a rather weak geometry of the problem and the monthly one week gap in the observations. Nevertheless, it will give a very useful external check on other competing methods (radio-interferometry, laser or radio-satellites).

Automated Determination of the Position of Ships by Satellites

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.

scholarly journals The Lunar orbit paradox

2013 ◽  
Vol 40 (1) ◽  
pp. 135-146
Author(s):  
Aleksandar Tomic
Keyword(s):  
Inertial Mass ◽  
Lunar Orbit ◽  
The Sun ◽  
The Moon ◽  
The Earth ◽  
Three Body ◽  
Origin Of The Moon ◽  
Force Intensity ◽  
Critical Consideration

Newton's formula for gravity force gives greather force intensity for atraction of the Moon by the Sun than atraction by the Earth. However, central body in lunar (primary) orbit is the Earth. So appeared paradox which were ignored from competent specialist, because the most important problem, determination of lunar orbit, was inmediately solved sufficiently by mathematical ingeniosity - introducing the Sun as dominant body in the three body system by Delaunay, 1860. On this way the lunar orbit paradox were not canceled. Vujicic made a owerview of principles of mechanics in year 1998, in critical consideration. As an example for application of corrected procedure he was obtained gravity law in some different form, which gave possibility to cancel paradox of lunar orbit. The formula of Vujicic, with our small adaptation, content two type of acceleration - related to inertial mass and related to gravity mass. So appears carried information on the origin of the Moon, and paradox cancels.

scholarly journals Commission 19: Rotation of the Earth

1985 ◽  
Vol 19 (1) ◽  
pp. 193-205 ◽  
Author(s):  
Ya. S. Yatskiv ◽  
W. J. Klepczynski ◽  
F. Barlier ◽  
H. Enslin ◽  
C. Kakuta ◽  
...  
Keyword(s):  
Time Frame ◽  
Laser Ranging ◽  
Earth’S Rotation ◽  
The Moon ◽  
Earth's Rotation ◽  
The Earth ◽  
Long Time ◽  
Terrestrial Reference System ◽  
Rotation Of The Earth

During the period, work on the problem of the Earth’s rotation has continued to expand and increase its scope. The total number of institutions engaged in the determination of the Earth’s rotation parameters (ERP) by different techniques has been increased significantly. The rotation of the Earth is currently measured by classical astrometry, Doppler and laser satellite tracking, laser ranging of the Moon, and radio interferometry. Several long time series of the ERP are available from most of these techniques, in particular, those made during the Main Campaign of the MERIT project. The various series have been intercompared and their stability, in the time frame of years to days, has been estimated for the purposes of establishing a new conventional terrestrial reference system (COTES). On the other hand, the difficulties of maintaining a regular operation for laser ranging to the Moon (LLR) have been recognized. It resulted in the proposal to organize an one-month campaign of observations in 1985 in order to complement the COTES collocation program and to allow additional intercomparisons with other techniques.

scholarly journals Accretion of the Moon from non-canonical discs

2014 ◽  
Vol 372 (2024) ◽  
pp. 20130256 ◽  
Author(s):  
J. Salmon ◽  
R. M Canup
Keyword(s):  
Angular Momentum ◽  
Rotation Period ◽  
Major Axis ◽  
The Moon ◽  
Large Excess ◽  
Semi Major Axis ◽  
Earth’S Mantle ◽  
The Earth ◽  
Post Impact ◽  
Impact Simulations

Impacts that leave the Earth–Moon system with a large excess in angular momentum have recently been advocated as a means of generating a protolunar disc with a composition that is nearly identical to that of the Earth's mantle. We here investigate the accretion of the Moon from discs generated by such ‘non-canonical’ impacts, which are typically more compact than discs produced by canonical impacts and have a higher fraction of their mass initially located inside the Roche limit. Our model predicts a similar overall accretional history for both canonical and non-canonical discs, with the Moon forming in three consecutive steps over hundreds of years. However, we find that, to yield a lunar-mass Moon, the more compact non-canonical discs must initially be more massive than implied by prior estimates, and only a few of the discs produced by impact simulations to date appear to meet this condition. Non-canonical impacts require that capture of the Moon into the evection resonance with the Sun reduced the Earth–Moon angular momentum by a factor of 2 or more. We find that the Moon's semi-major axis at the end of its accretion is approximately 7 R ⊕ , which is comparable to the location of the evection resonance for a post-impact Earth with a 2.5 h rotation period in the absence of a disc. Thus, the dynamics of the Moon's assembly may directly affect its ability to be captured into the resonance.

Chemical composition of the Moon's 'primary' crust – a clue at a terrestrial origin

2020 ◽  
Author(s):  
Audrey Vorburger ◽  
Peter Wurz ◽  
Manuel Scherf ◽  
Helmut Lammer ◽  
André Galli ◽  
...  
Keyword(s):  
Lunar Surface ◽  
Major Elements ◽  
The Moon ◽  
Lunar Crust ◽  
Near Surface ◽  
Origin And Evolution ◽  
The Past ◽  
The Earth ◽  
Terrestrial Origin ◽  
In The Beginning

<p>The Moon is one of the best characterized objects in space science, yet its origin still actively researched. Available orbital, geophysical, and geochemical information imposes clear restrictions on the origin and evolution of the Earth-Moon system (e.g., Canup 2008, 2012; Ćuk and Stewart 2012; Young et al. 2016). In regard to geochemical constraints, one of the most puzzling conundrums is posed by the similar isotopic fingerprints of the Earth and the Moon (e.g., Wiechert et al. 2001; Armytage et al. 2012; Zhang et al. 2012; Young et al. 2016; Schiller et al. 2018), together with the apparent lunar depletion in volatile elements (e.g., Ringwood and Kesson 1977; Wanke et al. 1977; Albarède et al. 2015; Taylor 2014). This apparent lunar volatile depletion is most notable in the low K content in comparison to U, a finding based on chemical analyses of samples collected from the lunar surface and lunar meteorites, and on spectroscopic observations of the lunar near-surface, despite both having been heavily processed in the past ~ 4.4 billion years.</p><p>In the past 4.4 billion years, space has been a harsh environment for our Moon, especially in the beginning, when the young Sun was still very active and the young Moon was continuously bombarded by meteorites of varying sizes. Solar wind and micro-meteoritic interactions with the lunar surface led to rapid and intensive processing of the lunar crust. Hence, the K/U depletion trend observable on today's lunar surface does not necessarily reflect a K/U ratio valid for the Moon in its entirety. We model the evolution of the abundances of the major elements over the past 4.3 to 4.4 billion years to derive the composition of the original lunar crust. Accounting for this processing, our model results show that the original crust is much less depleted in volatiles than the surface observable today, exhibiting a K/U ratio compatible with Earth and the other terrestrial planets, which strengthens the theory of a terrestrial origin for the Moon.</p>

scholarly journals Purnama-Tilem: Konsep Rwa Bhinneda Pada Wariga Di Bali

2020 ◽  
Vol 2 (1) ◽  
pp. 34
Author(s):  
Wasudewa Bhattacarya
Keyword(s):  
Full Moon ◽  
The Moon ◽  
Top Down ◽  
Dark Light ◽  
The Earth ◽  
The Difference ◽  
The Universe

<p><em>The spread of Hinduism from India to Indonesia is the result of acculturation of culture which then brought the concepts of Astronomy-Astrology in </em><em>Jyotiṣa </em><em>to Indonesia and Bali. Arriving in Bali, the concept of Astronomy-Astrology is known as Wariga. Wariga’s existence gave rise to holy days in the implementation of Yajña. One of them is the holy day of Purnama-Tilem. The determination of this holy day is based on the appearance of the moon from the earth as a repetitive cycle. If the moon appears perfectly round from the earth, it is called Purnama (Full Moon), whereas if the moon is not visible from the earth it is called Tilem (Dark Moon). This shows that there are two very basic differences in  determining Purnama  and  Tilem.  Dualistic this difference in Hinduism is called Rwa Bhinneda. Rwa Binneda is a polarization of life that speaks of all forms of dualism such as, top down, right left, dark light, and so on. Based on manuscipts in Bali, the existence of Purnama and Tilem shows a dualism in Hindu Theology called Sanghyang Rwa Bhinneda there  are Sanghyang Wulan and Sanghyang Surya at the level of </em><em>Saguṇa </em><em>Brahman. The dualism of the difference between Purnama and Tilem also influences Bhuwana Agung and Bhuwana Alit. The difference in the meaning of Purnama and Tilem is not something bad, but through this difference will bring about a balance between God, humans and the universe so that all beings will be able to reach the Moksartham Jagadhita ya ca iti Dharma.</em><em></em></p><p><strong><em><br /></em></strong><em></em><em></em></p>

scholarly journals Experimental Study of Torque Using a Small Scoop on the Lunar Surface

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Long Xue ◽  
Baichao Chen ◽  
Zhenjia Zhao ◽  
Zhaolong Dang ◽  
Meng Zou
Keyword(s):  
Experimental Study ◽  
Bulk Density ◽  
Lunar Surface ◽  
Great Influence ◽  
Test Results ◽  
The Moon ◽  
Rotating Speed ◽  
Simple Apparatus ◽  
The Earth

Chinese missions to the moon are planned to sample the regolith and return it to the earth. Microscale excavators may be good candidates for these missions, as they would significantly reduce the launch mass. Thus, it is necessary to research the interaction between the scoop and the regolith being sampled. We present the development of a simple apparatus to measure excavation torque. All tests were conducted using TYII-2 regolith simulant with gravels. The test results show that, under loose regolith conditions, the penetrating angle and the bulk density had a great influence on the excavation torque, while the rotating speed had little effect. However, when the bulk density was compact, the rotating speed did influence the excavation torque. The excavation torque increased sharply when the scoop encountered the gravels; actually, some of the parameters will influence the value of the torque such as the diameter, quantity, and position and inbuilt depth of the gravels. When the excavation torque sharply increases, the operation should be immediately stopped and checked.

New Economy in space: Cis-lunar economic circle and analogue simulations in China to the 2061 Horizon

2020 ◽  
Author(s):  
guo linli ◽  
blanc michel ◽  
huang tieqiu ◽  
huang jiangze ◽  
yuan jianping ◽  
...  
Keyword(s):  
International Cooperation ◽  
Lunar Surface ◽  
Space Exploration ◽  
Shaanxi Province ◽  
Lunar Exploration ◽  
Test Field ◽  
The Moon ◽  
Liquid Propellant ◽  
The Earth

&lt;p&gt;&amp;#160; &amp;#160; The Moon is sometimes also called the &quot;eighth continent&quot; of the Earth. Determining how to utilize cis-lunar orbital infrastructures and lunar resources to carry out new economic activities extended to the space of the Earth-Moon system is one of the long-term goals of lunar exploration activities around the world. Future long-term human deep-space exploration missions to the Moon, on the Moon surface or using the Moon to serve farther destinations will require the utilization of lunar surface or asteroid resources to produce water, oxygen and other consumables needed to maintain human survival and to produce liquid propellant for the supply of spacecraft on the lunar surface. In complement to exploration activities, Moon tourism in cis-lunar orbit and on the lunar surface will become more and more attractive with the increase of &amp;#160;human spaceflight capacity and the development of commercial space activities. However, the development of a sustainable Earth-Moon ecosystem requires that we solve the following five problems:&lt;/p&gt;&lt;p&gt;(1)How to design alow-cost cis-lunar space transportation capacity?&amp;#160;To find an optimal solution, one must compare&amp;#160;direct Earth-Moon flight modes with flights&amp;#160;based on&amp;#160;the utilization of&amp;#160;space stations, and identify the&amp;#160;most economical spacecraft architectures.&lt;/p&gt;&lt;p&gt;(2)How to design an efficient set ofcis-lunar&amp;#160;orbital&amp;#160;infrastructures combining LEO space stations, Earth-Moon L1/L2 point space stations and&amp;#160;Moon&amp;#160;bases&amp;#160;for commercial tourism, taking into account key issues such as energy,&amp;#160;communications and others?&lt;/p&gt;&lt;p&gt;(3)Significant amounts ofliquid oxygen, water,&amp;#160;liquid propellant&amp;#160;and structural material will be needed&amp;#160;for human bases, crew environmental control and life support systems, spacecraft propulsion systems, Moon surface storage and transportation&amp;#160;systems. How to &amp;#160;design in-situ resources utilization (ISRU) of the Moon, including its soil, rocks and polar&amp;#160;water ice reservoirs, to produce&amp;#160;the needed amounts?&lt;/p&gt;&lt;p&gt;(4) How to simulate on the Earth surface the different components and key technologies that will enable a future long-term human residence on the Moon surface?&lt;/p&gt;&lt;p&gt;(5). How to accommodate the co-development of&amp;#160;public and commercial&amp;#160;space&amp;#160;and foster international cooperation?&amp;#160;How can space policies and international space law help this co-development?&lt;/p&gt;&lt;p&gt;&amp;#160; &amp;#160; China has made rapid progress in robotic lunar exploration activities in the last 20 years, as illustrated by the recent discoveries provided by the Chang'e-4 lander on the far side of the Moon. By 2061, China will have gone into manned lunar exploration and built Moon bases. In preparation for this new phase of its contribution to space exploration, lunar surface simulation instruments have been built in Beijing, Shenzhen and other places in China. A series of achievements have been made in the field of space life sciences . An ambitious project to establish a large Moon base simulation test field, the Lunar Base Yulin (LBY) project, currently in its design phase in Yulin, Shaanxi Province in China, will allow the verification of key relevant technologies.&lt;/p&gt;&lt;p&gt;&amp;#160; &amp;#160; By the 2061 Horizon, we believe that international cooperation and public-private partnership will be key elements to enable this vision of a new, sustainable cis-lunar space economy.&lt;/p&gt;

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