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 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 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 Variations in the mean line of sight velocity of the Sun: 1976–1985

1988 ◽  
Vol 123 ◽  
pp. 215-218
Author(s):  
A. Jiménez ◽  
P.L. Pallé ◽  
C. Régulo ◽  
T. Roca Cortés ◽  
Y.P. Elsworth ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Mean Value ◽  
Red Shift ◽  
Line Of Sight ◽  
The Sun ◽  
Mean Values ◽  
The Mean ◽  
Shift Effect

Measurements of the line of sight velocity of the sun with respect to earth have been obtained at Izaña (Tenerife) during the years 1976 to 1985. The mean values found for each year show a trend of ~30 m/s from minimum to maximum. Their mean value is of 583.1 ± .2 m/s which is 92% of the gravitational red shift predicted by theory and their variation seems to be related to the solar cycle with the clear exception of 1985. The most likely interpretation is that the velocity limb shift effect, averaged over the whole sun, is the cause of the slight disagreement with theory and this effect changes with time.

scholarly journals I. On the period of hemispherical excess of sun-spots, and the 26-day period of terrestrial magnetism

1874 ◽  
Vol 22 (148-155) ◽  
pp. 42-44
Keyword(s):  
Magnetic Force ◽  
Mean Value ◽  
The Sun ◽  
Spot Area ◽  
Magnetic Action ◽  
Magnetic Period ◽  
Sun Spots ◽  
The Mean ◽  
The Difference ◽  
Northern And Southern Hemispheres

It appears from the interesting communication to the Royal Society, June 19th, by Messrs. De La Rue, Stewart, and Loewy, that the difference of the area of spots on the visible northern and southern quarter-spheres of the sun seems, during periods of considerable solar disturbance, to obey a law such that the difference is a maximum in the same quarter-sphere during several successive rotations of the sun, the difference being a maximum alternately in the northern and southern hemispheres—the time from maximum to maximum, for the same hemisphere, being variable between 18 and 32 days, but having a mean value of about 25-2 days. It occurs at once that if the variations of the mean terrestrial magnetic force are connected in any way with the solar spots, or the causes which produce them, we might here find some explanation of the magnetic period of 26 days, the difference of spot-area in one hemisphere from that in the other being related to a difference of the solar magnetic action.

scholarly journals Hamiltonian Theory of the Libration of the Moon

1978 ◽  
Vol 41 ◽  
pp. 125-135 ◽  
Author(s):  
Jacques Henrard ◽  
Michèle Moons
Keyword(s):  
Perturbation Technique ◽  
Mean Value ◽  
Canonical Transformations ◽  
The Moon ◽  
Physical Libration ◽  
Transform Method ◽  
Lie Transform ◽  
Hamiltonian Theory ◽  
The Mean ◽  
Free Libration

AbstractThe feasibility of applying the Lie transform method to the problem of the physical libration of the Moon is investigated. By a succession of canonical transformations, the Hamiltonian of the problem is brought under a form suitable for perturbation technique. The mean value of the inclination of the angular momentum upon the ecliptic and the frequencies of the free libration are computed.

ORIENTATION OF FEEDLOT BULLS WITH RESPECT TO THE SUN DURING PERIODS OF HIGH SOLAR RADIATION IN WINTER

1981 ◽  
Vol 61 (3) ◽  
pp. 809-816 ◽  
Author(s):  
H. W. GONYOU ◽  
W. R. STRICKLIN
Keyword(s):  
Solar Radiation ◽  
Air Temperature ◽  
Mean Value ◽  
Body Orientation ◽  
The Sun ◽  
Direct Radiation ◽  
High Solar Radiation ◽  
The Mean ◽  
Beef Bulls

Two experiments were conducted using yearling beef bulls to determine the relationships between body orientation and air temperature and solar radiation in winter. In exp. 1, observations were made at noon on 23 days from December to April to determine the orientation of 90 bulls as a deviation from an angle perpendicular to the sun's rays (ANG). The mean value of ANG for standing, non-eating bulls was 38.2°. In general, ANG decreased as direct radiation increased or temperature decreased. On cold sunny days, 53% of the standing bulls (n = 313) had ANG values of less than 20°, and the proportion decreased to only 31% of the bulls (n = 270)on warm cloudy days. In exp. 2, ANG was determined for 15 bulls at hourly intervals during the daylight hours on six occasions from January to April. Bulls stood closer to the perpendicular early in the day when temperatures were low, and when solar radiation was high. The results of these experiments indicated that bulls modified their body orientation to increase exposure to solar radiation on cold sunny days.

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 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 Trajectory optimization for the Horyu-VI international lunar mission

Astrodynamics ◽  
2021 ◽  
Author(s):  
Federico De Grossi ◽  
Paolo Marzioli ◽  
Mengu Cho ◽  
Fabio Santoni ◽  
Christian Circi
Keyword(s):  
Trajectory Optimization ◽  
Dust Particles ◽  
Gravity Gradient ◽  
The Sun ◽  
The Moon ◽  
Lunar Dust ◽  
The Earth ◽  
Lunar Mission ◽  
Solar Gravity ◽  
Key Parameter

AbstractThe Horyu-VI nano-satellite is an international lunar mission with the purpose of studying the lunar horizon glow (LHG)—a still unclear phenomenon caused by electrostatically charged lunar dust particles. This study analyzes the mission trajectory with the hypothesis that it is launched as a secondary payload of the NASA ARTEMIS-II mission. In particular, the effect of the solar gravity gradient is studied; in fact, depending on the starting relative position of the Moon, the Earth, and the Sun, the solar gradient acts differently on the trajectory—changing it significantly. Therefore, the transfer and lunar capture problem is solved in several cases with the initial Sun-Earth-Moon angle as the key parameter. Furthermore, the inclination with respect to the Moon at capture is constrained to be equatorial. Finally, the problem of stabilization and circularization of the lunar orbit is addressed in a specific case, providing an estimate of the total propellant cost to reach the final orbit around the Moon.

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