scholarly journals Precise Reduction to the Apparent Places of Stars

1974 ◽  
Vol 61 ◽  
pp. 319-319
Author(s):  
S. Yumi ◽  
K. Hurukawa ◽  
Th. Hirayama
Keyword(s):  
The Sun ◽  
Maximum Difference ◽  
The Moon ◽  
Uniform System ◽  
Outer Planets ◽  
The Mean ◽  
Astronomical Constants

For a precise reduction to the apparent places of the stars in a uniform system during the 19th and 20th centuries, the ‘Solar Coordinates 1800–2000’ by Herget (Astron. Papers14, 1953) may conveniently be used, because no coordinates of the Sun, referred to the mean equinox of 1950.0, are given in the Astronomical Ephemeris before 1930.A maximum difference of 0″.0003 was found between the aberrations calculated from both the Astronomical Ephemeris and Herget's Tables for the period 1960–1969, taking into consideration the effect of the outer planets, which amounted to 0″.0109.The effect of the inner planets on the aberration is estimated to be of the order of 0″.0001 at the most and the correction for the lunar term due to the change in astronomical constants is 0″.00002. It is recommended that the solar coordinates be calculated directly from Newcomb's formulae taking the effects of all the planets into consideration, but the effect concerned with the Moon can be neglected.

scholarly journals Effects of Solar Invasion on Earth Observation Sensors at a Moon-Based Platform

2019 ◽  
Vol 11 (23) ◽  
pp. 2775
Author(s):  
Hanlin Ye ◽  
Wei Zheng ◽  
Huadong Guo ◽  
Guang Liu ◽  
Jinsong Ping
Keyword(s):  
Mean Value ◽  
Earth Observation ◽  
The Sun ◽  
The Moon ◽  
Entrance Pupil ◽  
Evaluation Approach ◽  
The Mean ◽  
Potential Damage ◽  
Geometrical Relationship ◽  
Key Parameter

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, and this makes it possible to reduce solar invasion effects by selecting suitable regions to equip sensors. In this paper, methods for calculating the duration of the Sun entering of the sensor’s field of view (FOV) and the solar invasion radiation at the entrance pupil of the sensor are proposed. By deducing the expressions of the proposed geometrical relationship between the Sun, Earth, and Moon-based platform, it has been found that the key parameter to the effects of solar invasion is the angle between the Sun direction and the line-of-sight vector. Based on this parameter, both the duration and radiation can be calculated. In addition, an evaluation approach based on the mean value and standard deviation has been established to compare the variation of solar invasion radiation at different positions on the lunar surface. The results show that the duration is almost the same wherever the sensor is placed in the permanent Earth-observation region. Further, by comparing the variation of solar invasion radiation at different positions on the near-side of the Moon, we suggest that equipping sensors on the mid–high latitude regions within the permanent Earth-observation region will result in less solar invasion affects.

scholarly journals Indian Calendars

1987 ◽  
Vol 91 ◽  
pp. 91-95
Author(s):  
S.K. Chatterjee
Keyword(s):  
The Sun ◽  
The Moon ◽  
Star Group ◽  
Long Time ◽  
The Mean

The first treatise on calendric astronomy was compiled C1300 B.C.and is known as “The Vedāṅga Jyautiṣa. It gives rules for framing calendar covering a five-year period, called a ‘Yuga’. In this yuga-period calendar, there were 1830 civil days, 60 solar months, 62 synodic lunar months, and 67 sidereal lunar months. The calendar was luni-solar, and the year started from the first day of the bright fortnight when the Sun returned to the Delphini star group. Corrections were made, as required, to maintain this stipulation to the extent possible. The Vedāṅga calendar was framed on the mean motions of the luminaries, the Sun and the Moon, and was based on approximate values of their periods. Vedāṅga Jyautiṣa calendar remained in use for a very long time from C 1300 B.C. to C 400 A.D. when Siddhānta Jyautiṣa calendar based on true positions of the Sun and the Moon came into use and gradually replaced totally the Vedāṅga calendar.

scholarly journals Present Status of the Astronomical Ephemeris

1979 ◽  
Vol 81 ◽  
pp. 115-120 ◽  
Author(s):  
Sh. Aoki ◽  
A. M. Sinzi
Keyword(s):  
Present Status ◽  
Computer Programs ◽  
Astronomical Observatory ◽  
The Sun ◽  
Outer Planets ◽  
Numerical Integrations ◽  
Different Types ◽  
The Future ◽  
Astronomical Constants

The IAU (1976) System of Astronomical Constants and a new set of fundamental theories will expectedly be introduced into the international and national ephemerides for the volumes of 1984 onwards. In order to avoid any confusion in the future, it is necessary to manifest the character of the data published in the current volumes of the Astronomical Ephemeris = American Ephemeris, both abbreviated as A.E. With this end in view, computer programs for the calculations of the ephemerides of the Sun and inner planets based on the Newcomb's (1895, 1898) Tables have been prepared at Tokyo Astronomical Observatory (TAO) and Hydrographic Department of Japan (JHD) independently of each other using different computers and hence different types of FORTRAN. JHD has further prepared the programs for the Moon's ephemerides based on the Brown-Eckert theory and has reproduced the Eckert, Brouwer and Clemence's numerical integrations of the outer planets. Fundamental ephemerides thus calculated are compared with those data tabulated in the A.E. for the year of 1975, as an example, in the present paper.

scholarly journals Time Scales for Theory and Practice

1992 ◽  
Vol 9 ◽  
pp. 141-149
Author(s):  
Gernot M. R. Winkler
Keyword(s):  
Theory And Practice ◽  
The Sun ◽  
The Moon ◽  
Vernal Equinox ◽  
Perceived Needs ◽  
The Earth ◽  
Cyclical Process ◽  
The Mean ◽  
Complete Revolution ◽  
Early Human

Very early human experience has suggested a practical definition for the measurement of time: We define a unit of time by defining a standard (cyclical) process. Whenever this process completes its cycle identically, a unit of time has elapsed. This is the origin for the various measures of time in classical astronomy. Nature suggests strongly that we use as such standard processes the year (defined as a complete revolution of the earth around the Sun), the month (the completion of a revolution of the moon around the earth), and the day which again can be measured in several different ways. While the sidereal day is measured by a rotation in respect to the vernal equinox, the mean solar day is measured in respect to the mean. Sun. More recently, we have distinguished many more different ways of defining measures of time, partly in response to perceived needs of the applications, but in part also from purely aesthetic principles.

scholarly journals Planetary Ephemerides

1974 ◽  
Vol 3 ◽  
pp. 223-227
Author(s):  
R. L. Duncombe ◽  
P. K. Seidelmann ◽  
P. M. Janiczek
Keyword(s):  
Numerical Integration ◽  
The Moon ◽  
Outer Planets ◽  
Lunar Ephemeris ◽  
Empirical Corrections ◽  
Nautical Almanac ◽  
Astronomical Constants

At the present time the planetary ephemerides in the Astronomical Ephemeris and in the American Ephemeris and Nautical Almanac (both hereinafter referred to as the AE), the Astronomical Ephemeris of the U.S.S.R. and most other national almanacs have the following basis: For Mercury, Venus, Earth, and Mars the general theories of Simon Newcomb (1898a), the ephemeris of Mars including the empirical corrections determined by Ross (1917); for the five outer planets, the numerical integration of Eckert et al. (1951); the Connaissance de Temps publishes ephemerides of Mercury, Venus, Earth, and Mars based on the theories of Leverrier (1858, 1859, 1861a, b); for Jupiter, Saturn, Uranus, and Neptune the ephemerides are based on Leverrier’s (1876a, b, 1877a, b) expressions as modified by Gaillot (1904,1910, 1913). The ephemeris of Pluto is based on the numerical integration of Eckert et al. In all of the above publications the ephemeris of the Moon is now based on the Improved Lunar Ephemeris which is derived from the theory of Brown (1919). Newcomb’s theories and the numerical integration of the orbits of the five outer planets all rest primarily on the system of astronomical constants and planetary masses adopted at the Paris conferences of 1896 and 1911 {Monthly Notices Roy. Astron. Soc., 1912).

scholarly journals Moon’s Planetary Perturbations

1999 ◽  
Vol 172 ◽  
pp. 413-414
Author(s):  
P. Bidart ◽  
J. Chapront
Keyword(s):  
Reference Plane ◽  
Rotating Frame ◽  
The Sun ◽  
The Moon ◽  
Keplerian Motion ◽  
The Earth ◽  
Brown's Method ◽  
Numerical Tools ◽  
The Mean ◽  
Under Construction

In ELP, the computation of planetary perturbations is about 20 years old. A better knowledge of lunar and planetary parameters, new planetary solutions under construction and progresses in numerical tools, are factors that should contribute to their improvements. The construction of planetary perturbations takes widely its inspiration from Brown’s method. In a first step, we only consider the main problem (Earth, Moon, and Sun with a Keplerian motion). The solution of the main problem is actually of a high precision and is used as a reference (Chapront-Touzé, 1980). This solution is expressed in Fourier series of the 4 Delaunay arguments, with numerical coefficients, and partials with respect to integration constants.The method based on the variation of arbitrary constants is described in (M.Chapront-Touzé, J.Chapront, 1980). Equations of Moon’s motion are written in a rotating frame where the reference plane is the mean ecliptic. In this frame, the absolutec acceleration is expressed by means of disturbing forces acting on the Moon, by the Sun, the Earth and a planet. It is the gradient of F which can be divided into several components: Fc related to the main problem, FD and FI giving rise to direct and indirect planetary perturbations.

scholarly journals System of Astronomical Constants in Hindu Astronomy

1987 ◽  
Vol 91 ◽  
pp. 85-89
Author(s):  
Amalendu Bandyopadhyay ◽  
Ashok Kumar Bhatnagar
Keyword(s):  
The Sun ◽  
The Moon ◽  
Astronomical Constants

AbstractAstronomical constants such as the length of the solar year, sidereal and synodic periods of revolutions of the Moon and five brighter planets have been computed using the system of astronomy in ancient and mediaeval India and a comparison made with their modern values. The modern values of the Moon’s inequalities have been compared with that of the earlier Hindu astronomical reckonings. Also, the Equation of the Centre of the Sun as determined in the period 500 A.D. to 1150 A.D. has been discussed in relation to corresponding modern values.

I. On the lunar variations of magnetic declination at Bombay

1872 ◽  
Vol 20 (130-138) ◽  
pp. 135-136
Keyword(s):  
Diurnal Variation ◽  
Relative Position ◽  
Diurnal Variations ◽  
The Sun ◽  
The Moon ◽  
Feature Correspondence ◽  
Magnetic Declination ◽  
Variation Curve ◽  
Ordinary Character ◽  
The Mean

This paper is in continuation of that “On the Solar Variations of Magnetic Declination at Bombay,” published in the Philosophical Transactions for 1869; but the discussion is confined to the observations of the years 1861 to 1863, which alone have as yet been reduced. The point of principal interest brought out in the discussion is that whilst the mean lunar-diurnal variation is of the ordinary character, having as its principal feature a double oscillation in the lunar day, its range is very small as compared with the several ranges of the lunar-diurnal variations when the sun and moon have several specific varieties of relative position; and moreover, although in those latter variations the double oscillation is generally preserved as a main feature, correspondence of phase in the representative curves is as generally absent; and in some cases the curves are, whilst systematic, altogether different in character from the mean lunar-diurnal variation curve. The semiannual inequality in the lunar-diurnal variation, whilst it is as definitely systematic, has twice the range of the mean lunar, diurnal variation; and it is also subject to remarkable modifications which accompany changes of phase of the moon.

The motion of a lunar orbiter

1966 ◽  
Vol 25 ◽  
pp. 373
Author(s):  
Y. Kozai
Keyword(s):  
Degrees Of Freedom ◽  
Dimensional Space ◽  
Artificial Satellite ◽  
Equations Of Motion ◽  
Triaxial Ellipsoid ◽  
The Moon ◽  
Secular Motion ◽  
The Earth ◽  
Close Satellite ◽  
The Mean

The motion of an artificial satellite around the Moon is much more complicated than that around the Earth, since the shape of the Moon is a triaxial ellipsoid and the effect of the Earth on the motion is very important even for a very close satellite.The differential equations of motion of the satellite are written in canonical form of three degrees of freedom with time depending Hamiltonian. By eliminating short-periodic terms depending on the mean longitude of the satellite and by assuming that the Earth is moving on the lunar equator, however, the equations are reduced to those of two degrees of freedom with an energy integral.Since the mean motion of the Earth around the Moon is more rapid than the secular motion of the argument of pericentre of the satellite by a factor of one order, the terms depending on the longitude of the Earth can be eliminated, and the degree of freedom is reduced to one.Then the motion can be discussed by drawing equi-energy curves in two-dimensional space. According to these figures satellites with high inclination have large possibilities of falling down to the lunar surface even if the initial eccentricities are very small.The principal properties of the motion are not changed even if plausible values ofJ3andJ4of the Moon are included.This paper has been published in Publ. astr. Soc.Japan15, 301, 1963.

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