We consider the dynamical evolution of planetary systems whose structure is nearly circular and coplanar. The analysis is performed by the Hori–Deprit averaging method within the theory of the first ...order in planetary masses. A convenient set of canonical elements and a rarely employed variety of astrocentric coordinates are used to derive the equations of motion. Owing to the use of the chosen system of canonical elements, the expansions of the right-hand sides of the averaged equations contain a relatively small number of terms. Compared to other widespread coordinate systems, the astrocentric coordinates used by us allow a more convenient representation of the disturbing function to be obtained and do not require its expansion into a series in powers of a small parameter. On time scales
years we have studied the long-term evolution of the planetary systems HD 12661,
Andromedae, and some model systems by numerical integration of the averaged equations. Possible secular resonances have been revealed in the systems considered.
We investigate the heliocentric in-orbit repositioning problem of a spacecraft propelled by an Electric Solar Wind Sail. Given an initial circular parking orbit, we look for the heliocentric ...trajectory that minimizes the time required for the spacecraft to change its azimuthal position, along the initial orbit, of a (prescribed) phasing angle. The in-orbit repositioning problem can be solved using either a drift ahead or a drift behind maneuver and, in general, the flight times for the two cases are different for a given value of the phasing angle. However, there exists a critical azimuthal position, whose value is numerically found, which univocally establishes whether a drift ahead or behind trajectory is superior in terms of flight time it requires for the maneuver to be completed. We solve the optimization problem using an indirect approach for different values of both the spacecraft maximum propulsive acceleration and the phasing angle, and the solution is then specialized to a repositioning problem along the Earth's heliocentric orbit. Finally, we use the simulation results to obtain a first order estimate of the minimum flight times for a scientific mission towards triangular Lagrangian points of the Sun−Earth+Moon system.
•This paper analyzes the in-orbit repositioning of an E-sail-based vehicle.•The problem is studied by evaluating the minimum flight time.•A mission towards Sun–Earth triangular Lagrangian points is discussed.
Рассматривается некомпланарный управляемый гелиоцентрический перелёт космического аппарата с неидеально отражающим солнечным парусом к Венере. Целью гелиоцентрического движения является попадание ...космического аппарата в сферу Хилла Венеры с нулевым гиперболическим избытком скорости. Для реализации перелёта разработан алгоритм применения законов локально-оптимального управления для наискорейшего изменения оскулирующих элементов. Управление ориентацией солнечного паруса осуществляется с помощью тонкоплёночных элементов управления, расположенных по периметру поверхности солнечного паруса. В результате моделирования движения определены траектория перелёта, программа управления и необходимые ширина и площадь тонкоплёночных элементов управления.
On 24 September 2014 India became the first country to put an interplanetary space probe around Mars in her first attempt. Mars Orbiter Mission, popularly known as MOM, was earlier launched from ...Sriharikota using a Polar Satellite Launch Vehicle (PSLV) rocket on 5 November 2013. After a cruise phase of 300 days in the heliocentric orbit, MOM is now going around Mars in an elliptical orbit. The spacecraft is now circling Mars in an orbit whose nearest point to Mars (periapsis) is at 424 km and farthest point (apoapsis) at 77, 098 km. The inclination of orbit with respect to the equatorial plane of Mars is ~150 degree, as intended.
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BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The space radiation dose over air routes including polar routes should be carefully considered, especially when space weather shows sudden disturbances such as coronal mass ejections (CMEs), flares, ...and accompanying solar energetic particle events. We recently established a heliocentric potential (HCP) prediction model for real-time operation of the CARI-6 and CARI-6M programs. Specifically, the HCP value is used as a critical input value in the CARI-6/6M programs, which estimate the aviation route dose based on the effective dose rate. The CARI-6/6M approach is the most widely used technique, and the programs can be obtained from the U.S. Federal Aviation Administration (FAA). However, HCP values are given at a one month delay on the FAA official webpage, which makes it difficult to obtain real-time information on the aviation route dose. In order to overcome this critical limitation regarding the time delay for space weather customers, we developed a HCP prediction model based on sunspot number variations (Hwang et al. 2015). In this paper, we focus on improvements to our HCP prediction model and update it with neutron monitoring data. We found that the most accurate method to derive the HCP value involves (1) real-time daily sunspot assessments, (2) predictions of the daily HCP by our prediction algorithm, and (3) calculations of the resultant daily effective dose rate. Additionally, we also derived the HCP prediction algorithm in this paper by using ground neutron counts. With the compensation stemming from the use of ground neutron count data, the newly developed HCP prediction model was improved.
Johannes Kepler accepted Tycho Brahe's claim that the Copernican hypothesis required all stars to be giant, something Brake found absurd. Kepler argued in his De Stella Nova that some stars were ...larger than Brahe's size for the entire universe. He also used the issue of star sizes to argue against Giordano Bruno's infinite universe. Kepler's acceptance of Brahe's ideas on star sizes appears in a variety of his writings, including his response to the anti-Copernican essay by Msgr. Francesco Ingoli that cited the star size issue, an essay Galileo had felt was influential in the rejection of the Copernican hypothesis by authorities in Rome in 1616. Kepler's writings illustrate how certain supporters of Copernicus viewed the universe of stars and relied on divine power to undergird that view. Decades after Kepler, the discovery that the star size problem rested on a formerly unrecognized optical effect both freed the Copernican hypothesis from Brahe's charge of absurdity and negated Kepler's argument against Bruno.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A system of averaged equations of planetary motion around a central star is constructed. An astrocentric coordinate system is used. The two-planet problem is considered, but all constructions are ...easily generalized to an arbitrary number
N
of planets. The motion is investigated in modified (complex) Poincarécanonical elements. The averaging is performed by the Hori–Deprit method over the fast mean longitudes to the second order relative to the planetary masses. An expansion of the disturbing function is constructed using the Laplace coefficients. Some terms of the expansion of the disturbing function and the first terms of the expansion of the averaged Hamiltonian are given. The results of this paper can be used to investigate the evolution of orbits with moderate eccentricities and inclinations in various planetary systems.
This paper introduces a simple analytical approximation to three-dimensional heliocentric solar sail orbits where the only forces considered are solar gravity and solar radiation. The approximation ...is based upon the previously studied hodograph transformation and provides a description of the inclination, longitude of ascending node and true latitude for a specific set of initial conditions. It is shown that the rotational symmetry of a heliocentric orbit allows this specific solution to be mapped onto a solution with arbitrary initial conditions. The approximation is then compared to the numerical results for a solar sail on an Earth escape trajectory with an area to mass ratio up to twice as high as current technology allows.
The paper discusses Tycho Brahe’s geo-heliocentric system, arguing that it represents a good instance of a failed synthesis. First, the Author analyzes the physical and metaphysical principles ...grounding this system, relying on Brahe’s correspondence with Christoph Rothmann. The popular anti-Copernican arguments of the tower and of the cannon, which Galileo would try to refute in his Dialogue Concerning the Two Chief World Systems, find here their first formulation. Secondly, some theoretical problems of Tycho’s system are discussed, intending also to clarify Galileo’s ambiguous attitude towards him. Indeed, although Brahe is surely the major polemical reference of Galileo’s Dialogue, he is never explicitly mentioned therein. This is because, as Galileo says, Tycho was never able to provide a thorough description of a system of the world comparable to those of Ptolemy and of Copernicus. Brahe’s system may thus be characterized as the last great attempt to synthetize the old and the new, before the risk of the collapse of the traditional cosmos: attempt which, considering the growing success of the heliocentric model, was inevitably doomed to failure.
In this research we search for a functional dependence between the occurrence
of forest fires in the USA and the factors which characterize the solar
activity. For this purpose we used several ...methods (R/S analysis, Hurst
index) to establish potential links between the influx of some parameters
from the sun and the occurrence of forest fires with lag of several days. We
found evidence for a connection and developed a prognostic scenario based on
the Adaptive neuro-fuzzy interference system (ANFIS) technique. This scenario
allows the prediction between 79-93% of forest fires.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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