Coverage Analysis of Lunar Communication/Navigation Constellations Based on Halo Orbits and Distant Retrograde Orbits

2020 ◽  
Vol 73 (4) ◽  
pp. 932-952
Author(s):  
Zhao-Yang Gao ◽  
Xi-Yun Hou
Keyword(s):  
Lunar Surface ◽  
Polar Regions ◽  
The Moon ◽  
Halo Orbits ◽  
Satellite Constellation ◽  
The North ◽  
Polar Caps ◽  
Distant Retrograde Orbits ◽  
Distant Retrograde Orbit ◽  
South Polar

AbstractWith more and more missions around the Moon, a communication/navigation constellation around the Moon is necessary. Halo orbits, due to their unique geometry, are extensively studied by researchers for this purpose. A dedicated survey is carried out in this work to analyse the coverage ability of halo orbits. It is found that a two-satellite constellation is enough for continuous one-fold coverage of the north or the south polar regions but never both. A three-satellite constellation is enough for continuous one-fold coverage of both north and south polar regions. A four-satellite constellation can cover nearly 100% of the whole lunar surface. In addition, the coverage ability of another special orbit – distant retrograde orbit (DRO) – is analysed for the first time in this study. It is found that three satellites on DROs can cover 99·8% of the lunar surface, with coverage gaps at polar caps. A four-satellite constellation moving on spatial DROs can cover nearly the whole lunar surface. By combining halo orbits and DROs, we design a five-satellite constellation composed of three halo orbit satellites and two DRO satellites. This constellation can provide 100% continuous one-fold coverage of the whole lunar surface.

scholarly journals Storm enhanced density: magnetic conjugacy effects

2007 ◽  
Vol 25 (8) ◽  
pp. 1791-1799 ◽  
Author(s):  
J. C. Foster ◽  
W. Rideout
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Ionospheric Disturbance ◽  
Polar Regions ◽  
The North ◽  
Polar Caps ◽  
Source Regions ◽  
Field Lines ◽  
Magnetic Conjugacy ◽  
Early Phases

Abstract. In the early phases of a geomagnetic storm, the low and mid-latitude ionosphere are greatly perturbed. Large SAPS electric fields map earthward from the perturbed ring current overlapping and eroding the outer plasmasphere and mid-latitude ionosphere, drawing out extended plumes of storm enhanced density (SED). We use combined satellite and ground-based observations to investigate the degree of magnetic conjugacy associated with specific features of the stormtime ionospheric perturbation. We find that many ionospheric disturbance features exhibit degrees of magnetic conjugacy and simultaneity which implicate the workings of electric fields. TEC enhancements on inner-magnetospheric field lines at the base of the SED plumes exhibit localized and longitude-dependent features which are not strictly magnetic conjugate. The SED plumes streaming away from these source regions closely follow magnetic conjugate paths. SED plumes can be used as a tracer of the location and strength of disturbance electric fields. The SED streams of cold plasma from lower latitudes enter the polar caps near noon, forming conjugate tongues of ionization over the polar regions. SED plumes exhibit close magnetic conjugacy, confirming that SED is a convection electric field dominated effect. Several conclusions are reached: 1) The SED plume occurs in magnetically-conjugate regions in both hemispheres. 2) The position of the sharp poleward edge of the SED plume is closely conjugate. 3) The SAPS electric field is observed in magnetically conjugate regions (SAPS channel). 4) The strong TEC enhancement at the base of the SED plume in the north American sector is more extensive than in its magnetic conjugate region. 5) The entry of the SED plume into the polar cap near noon, forming the polar tongue of ionization (TOI), is seen in both hemispheres in magnetically-conjugate regions.

Analysis of the evolution of Martian polar caps during Martian Years 34-35 from Mars Express Visual Monitoring Camera

2021 ◽  
Author(s):  
Teresa del Río-Gaztelurrutia ◽  
Agustín Sánchez-Lavega ◽  
Jorge Hernández-Bernal ◽  
Ainhoa Angulo ◽  
Ricardo Hueso ◽  
...  
Keyword(s):  
Dust Storm ◽  
Wide Field ◽  
Polar Regions ◽  
Visual Monitoring ◽  
Mars Express ◽  
Ice Caps ◽  
Regression Curves ◽  
Polar Caps ◽  
Monitoring Camera ◽  
South Polar

<p>The wide field of view of the Visual Monitoring Camera (VMC) onboard Mars Express, together with the polar orbit of the spacecraft, make VMC very suitable to monitor polar phenomena on Mars<sup>1</sup>. During Martian Years 34 and 35, Martian polar regions were imaged regularly by VMC, and in this work we use this set of images to analyze the evolution of both north and south polar ice caps. We determine the limits of the ice cap at different longitudes and the total area covered by ice as the season evolves, and we analyze the possible influence of the Global Dust Storm in the evolution of the ice caps regression curves. Finally, we describe a number of mid-scale atmospheric features that develop at the edge of the polar caps.</p><p><sup>1</sup> Hernandez-Bernal et al. ”The 2018 Martian Global Dust Storm Over the South Polar Region Studied With MEx/VMC” Geophys. Res. Lett. 46, pp 10330-10337 (2019)</p>

scholarly journals Analysis of Long-Term Moon-Based Observation Characteristics for Arctic and Antarctic

2019 ◽  
Vol 11 (23) ◽  
pp. 2805 ◽  
Author(s):  
Yue Sui ◽  
Huadong Guo ◽  
Guang Liu ◽  
Yuanzhen Ren
Keyword(s):  
Global Climate Change ◽  
Large Scale ◽  
Global Climate ◽  
Earth Observation ◽  
Polar Regions ◽  
The Moon ◽  
The North ◽  
The Earth ◽  
The Antarctic

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 to the satellite-based Earth observation data, it is necessary to study the observation characteristics of this new platform. With deepening understanding of Moon-based observations, we have seen its good observation ability in the middle and low latitudes of the Earth’s surface, but for polar regions, we need to further study the observation characteristics of this platform. Based on the above objectives, we used the Moon-based Earth observation geometric model to quantify the geometric relationship between the Sun, Moon, and Earth. Assuming the sensor is at the center of the nearside of the Moon, the coverage characteristics of the earth feature points are counted. The observation intervals, access frequency, and the angle information of each point during 100 years were obtained, and the variation rule was analyzed. The research showed that the lunar platform could carry out ideal observations for the polar regions. For the North and South poles, a continuous observation duration of 14.5 days could be obtained, and as the latitude decreased, the duration time was reduced to less than one day at the latitude of 65° in each hemisphere. The dominant observation time of the North Pole is concentrated from mid-March to mid-September, and for the South Pole, it is the rest of the year, and as the latitude decreases, it extends outward from both sides. The annual coverage time and frequency will change with the relationship between the Moon and the Earth. This study also proves that the Moon-based observation has multi-angle observation advantages for the Arctic and the Antarctic areas, which can help better understand large-scale geoscientific phenomena. The above findings indicate that the Moon-based observation can be applied as a new type of remote sensing technology to the observation field of the Earth’s polar regions.

scholarly journals Some Differences Between Geometrical and Dynamical Figures of the Moon

1972 ◽  
Vol 47 ◽  
pp. 32-34 ◽  
Author(s):  
I. V. Gavrilov
Keyword(s):  
Gravity Field ◽  
Lunar Surface ◽  
Homogeneous Model ◽  
Artificial Satellites ◽  
Geometrical Shape ◽  
The Moon ◽  
Geometrical Figure ◽  
Centre Of Gravity ◽  
The North ◽  
The Earth

The geometrical shape of the Moon is determined from measurements of absolute heights of the lunar surface, while its dynamical shape is described by means of the Moon's gravity field parameters. All these data are derived from observations of the lunar artificial satellites (‘Luna-10’, ‘Orbiters 1-4’) and astronomical measurements.In the paper differences of the lunar geometrical and dynamical figures are analysed. It is shown, that the homogeneous model of the Moon is not capable of explaining these differences. It is found, that the lunar centre of gravity situated about 0.9 km to the north, and 1.1 km nearer to the Earth, than the centre of its geometrical figure.

scholarly journals Direct evidence of surface exposed water ice in the lunar polar regions

2018 ◽  
Vol 115 (36) ◽  
pp. 8907-8912 ◽  
Author(s):  
Shuai Li ◽  
Paul G. Lucey ◽  
Ralph E. Milliken ◽  
Paul O. Hayne ◽  
Elizabeth Fisher ◽  
...  
Keyword(s):  
Lunar Surface ◽  
Near Infrared ◽  
Direct Evidence ◽  
Polar Regions ◽  
The Moon ◽  
Optical Surface ◽  
Laser Altimeter ◽  
Polar Wander ◽  
Water Ice ◽  
Maximum Temperatures

Water ice may be allowed to accumulate in permanently shaded regions on airless bodies in the inner solar system such as Mercury, the Moon, and Ceres [Watson K, et al. (1961)J Geophys Res66:3033–3045]. Unlike Mercury and Ceres, direct evidence for water ice exposed at the lunar surface has remained elusive. We utilize indirect lighting in regions of permanent shadow to report the detection of diagnostic near-infrared absorption features of water ice in reflectance spectra acquired by the Moon Mineralogy Mapper [M (3)] instrument. Several thousand M (3) pixels (∼280 × 280 m) with signatures of water ice at the optical surface (depth of less than a few millimeters) are identified within 20° latitude of both poles, including locations where independent measurements have suggested that water ice may be present. Most ice locations detected in M (3) data also exhibit lunar orbiter laser altimeter reflectance values and Lyman Alpha Mapping Project instrument UV ratio values consistent with the presence of water ice and also exhibit annual maximum temperatures below 110 K. However, only ∼3.5% of cold traps exhibit ice exposures. Spectral modeling shows that some ice-bearing pixels may contain ∼30 wt % ice that is intimately mixed with dry regolith. The patchy distribution and low abundance of lunar surface-exposed water ice might be associated with the true polar wander and impact gardening. The observation of spectral features of H2O confirms that water ice is trapped and accumulates in permanently shadowed regions of the Moon, and in some locations, it is exposed at the modern optical surface.

scholarly journals XVI. Contributions to terrestrial magnetism.—No. XIII

1872 ◽  
Vol 162 ◽  
pp. 353-433 ◽  
Keyword(s):  
Secular Change ◽  
Magnetic Survey ◽  
Polar Regions ◽  
Present Communication ◽  
The South ◽  
Present Contribution ◽  
Terrestrial Magnetism ◽  
The North ◽  
North Polar ◽  
South Polar

In this, the XIII.th Number of the “Contributions to Terrestrial Magnetism,” I have the pleasure of presenting to the Royal Society the Magnetic Survey of the North Polar Regions of the Globe, in a suitable form and arrangement to entitle it to be regarded as a companion to the Magnetic Survey of the South Polar Regions, presented to the Society in 1868; constituting, with the present contribution, a moiety of the Magnetic Survey of the Globe corresponding to the general epoch 1840 to 1845. The area com­prised in the present communication is coextensive with that of the South Polar Survey, and the epochs are the same, viz. 1840 to 1845, or more simply 1842.5; the chief distinction between the two surveys being, that the South Polar Survey is the work of a single nation,—executed by the authority of its Government and at the national expense in the brief interval comprised between the years 1840 and 1845, and thus requiring no corrections to be introduced for secular change, a troublesome and not very certain operation; whilst its companion, the present communication, comprehends the coopera­tive labours of many European and American contributors, acting for the most part independently of each other, within the limits of about twenty years preceding, and twenty years following, the mean epoch of 1842.5: the results, therefore, when brought together, require the introduction of “ corrections for secular change,” where these are practicable, and where they can be made with safety.

Water on Mars: The Real Deal

2020 ◽  
pp. 77-88
Author(s):  
David A. Weintraub
Keyword(s):  
Thin Layer ◽  
Lake Ontario ◽  
Significant Evidence ◽  
Melting Snow ◽  
The North ◽  
Polar Caps ◽  
Water On Mars ◽  
North And South ◽  
Recent Epoch ◽  
South Polar

This chapter talks about the astronomers that have solved some of the riddles of how much water Mars had and still has, a century and a half after William Huggins first proved that Mars had water. It highlights that Mars' water was no longer in the liquid state on the surface as the planet had become much dryer after billions of years. It also examines significant evidence that strongly suggests that Mars experienced a more recent epoch when water carved valleys and was formed from melting snow and ice that flowed slowly into and out of chains of lakes. The chapter describes one of Mars' lakes that appears to have been widespread both north and south of the Martian equator, containing more water than Lake Ontario. It discusses Mars' layered ice deposits at the north and south polar caps, in which a thin layer is deposited each Martian winter and then sublimates in Martian spring.

A Photographic Map of the Moon

1962 ◽  
Vol 14 ◽  
pp. 113-115
Author(s):  
D. W. G. Arthur ◽  
E. A. Whitaker
Keyword(s):  
Lunar Surface ◽  
The Moon ◽  
Map Projection

The cartography of the lunar surface can be split into two operations which can be carried on quite independently. The first, which is also the most laborious, is the interpretation of the lunar photographs into the symbolism of the map, with the addition of fine details from telescopic sketches. An example of this kind of work is contained in Johann Krieger'sMond Atlaswhich consists of photographic enlargements in which Krieger has sharpened up the detail to accord with his telescopic impressions. Krieger did not go on either to convert the photographic picture into the line symbolism of a map, or to place this picture on any definite map projection.

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