52,396 research outputs found
Orbit determination and control for the European Student Moon Orbiter
No full textThis paper presents the preliminary navigation and orbit determination analyses for the European Student Moon Orbiter. The severe constraint on the total mission Delta nu and the all-day piggy-back launch requirement imposed by the limited available budget, led to the choice of using a low-energy transfer, more specifically a Weak Stability Boundary one, with a capture into an elliptic orbit around the Moon. A particular navigation strategy was devised to ensure capture and fulfil the requirement for the uncontrolled orbit stability at the Moon. This paper presents a simulation of the orbit determination process, based on an extended Kalman filter, and the navigation strategy applied to the baseline transfer of the 2011-2012 window. The navigation strategy optimally allocates multiple Trajectory Correction Manoeuvres to target a so-called capture corridor. The capture corridor is defined, at each point along the transfer, by back-propagating the set of perturbed states at the Moon that provides an acceptable lifetime of the lunar orbit. (C) 2012 Elsevier Ltd. All rights reserved
Letter to F.D. Moon from Louis H. Ritzhaunt regarding a bill to transfer of administration for Langston University to the Board of Agriculture
No full textLetter to F.D. Moon regarding SB 104 transferring the power of administration for Langston University to the Board of Agriculture
Moon Phases, Mood and Stock Market Returns: International Evidence
No full textWe employ recent data from 59 international emerging and mature stock markets to provide new evidence of a lunar cycle (full and new moon) effect on their stock market returns. Using a TGARCH model, we further examine the linkages between efficient-market theory, calendar-related effects and investors' mood resulted from moon phases. The empirical results show significant full moon effects in 6 markets, and significant new moon effects in 8 markets. In line with the theory, we report significant positive effect of new moon on stock market returns in 5 cases (UK, Switzerland, Bangladesh, Chile and Cyprus), while a negative effect of full moon is reported for the case of Jordan only. In addition, we find that lunar effects are strongly influenced by the calendar anomalies (Monday effect and January effect); several markets -mostly emerging markets- show evidence of full/new moon effects as well as Monday/January effects (Bangladesh, Brazil, Chile, Tunisia, Belgium, Cyprus). Further, we prove that the lunar phases are stronger outside America. These findings are recommended to investors, financial managers and analysts dealing with international stock indices
Letter to F.D. Moon from H.C. McCormick regarding a letter of introduction
No full textLetter to F.D. Moon thanking him for a letter of introductio
Low-thrust trajectories design for the European Student Moon Orbiter mission
No full textThe following paper presents the mission analysis studies performed for the phase A of the solar electric propulsion option of the European Student Moon Orbiter (ESMO) mission. ESMO is scheduled to be launched in 2011, as an auxiliary payload on board of Ariane 5. Hence the launch date will be imposed by the primary payload. A method to efficiently assess wide launch windows for the Earth-Moon transfer is presented here. Sets of spirals starting from the GTO were propagated forward with a continuous tangential thrust until reaching an apogee of 280,000 km. Concurrently, sets of potential Moon spirals were propagated backwards from the lunar orbit injection. The method consists of ranking all the admissible lunar spiral-down orbits that arrive to the target orbit with a simple tangential thrust profile after a capture through the L1 Lagrange point. The 'best' lunar spiral is selected for each Earth spiral. Finally,comparing the value of the ranking function for each launch date, the favourable and unfavourable launch windows are identified
A 3D hybrid simulation study of the electromagnetic field distributions in the lunar wake
No full textAs a consequence of its lack of a thick atmosphere and an ionosphere,
the interaction of the solar wind with the Moon is characterized
by the direct impact of the solar wind on its sunward
hemisphere. This absorption effect produces a near-vacuum in the
wake immediately behind the Moon. The absence of a global magnetosphere
and the low electrical conductivity further leads to the
free passage of the interplanetary magnetic field (IMF) through the
lunar interior. This classic scenario of the solar wind�Moon interaction
was established by the very first plasma measurements in the
lunar environment made by the Explorer 35 spacecraft (Lyon et al.,
1967; Schubert and Lichtenstein, 1974). The wake region is gradually
filled in by the diffusion of solar wind protons into the zone of
density depletion. As described in the early analyses by Michel
(1968) and Whang and Ness (1970), the expansion of the solar wind
plasma into the wake is accompanied by rarefaction waves. At the
same time, the magnetometer experiment on Explorer 35 detected
the existence of a field reduction zone at the wake boundary surrounding
the central region, with magnetic field enhancement up
to a factor of 1.4 in comparison to the value in the ambient solar
wind (Colburn et al., 1967). Some of these features were repeatedly
observed at different distances in the lunar wake by the Win
Bench Crater Meteorite: Hydrated Asteroidal Material Delivered to the Moon
Get PDFD/H measurements from the lunar regolith agglutinates [8] indicate mixing between a low D/H solar implanted component and additional higher D/H sources (e.g., meteoritic/ cometary/volcanic gases). We have determined the range and average D/H ratio of Bench Crater meteorite, which is the first direct D/H analysis of meteoritic material delivered to the lunar surface. This result provides an important ground truth for future investigations of lunar water resources by missions to the Moon
Solar sail trajectories at the Earth-Moon Lagrange points
No full textPaper presented during Session 3, Orbital Dynamics, Symposium C1, Astrodynamics, Paper Number 13. This paper investigates displaced periodic orbits at linear order in the circular restricted Earth-Moon system, where the third massless body is a solar sail. These highly non-Keplerian orbits are achieved using an extremely small sail acceleration. The solar sail Earth-Moon system differs greatly from the Earth-Sun system as the Sun line direction varies continuously in the rotating frame and the equations of motion of the sail are given by a set of nonlinear non-autonomous ordinary differential equations. By introducing a first-order approximation, periodic orbits are derived analytically at linear order. These approximate analytical solutions are utilized in a numerical search to determine displaced periodic orbits in the full nonlinear model. The importance of finding such displaced orbits is to obtain continuous communications between the equatorial regions of the Earth and the polar regions of the Moon. As will be shown, displaced periodic orbits exist at all Lagrange points at linear order
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Vitamin D, and maternal and child health
No full textVitamin D has important roles in calcium metabolism and the prevention of rickets and osteomalacia; low levels of 25-hydroxyvitamin D are common in general population and amongst pregnant women. Whilst there is a wealth of observational evidence linking vitamin D deficiency to a wide range of disease outcomes, there are currently few high quality randomised controlled trials to confirm any causal associations, although many are currently in progress. Furthermore, currently, the vast majority of published guidelines recommend standard supplemental vitamin D doses for children and pregnant women, yet there is increasing recognition that individual characteristics and genetic factors may influence the response to supplementation. As such, future research needs to concentrate on documenting definite beneficial clinical outcomes of vitamin D supplementation, and establishing personalised dosing schedules and demonstrating effective approaches to optimizing initiation and adherence
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