67,372 research outputs found
Letter to F.D. Moon from J. Woods regarding thanking Moon for a good experience working at Douglass High School
No full textLetter to F.D. Moon expressing thanks for a good experience working at Douglass High School
Evidence for the decay B0→J/ψω and measurement of the relative branching fractions of meson decays to J/ψη and J/ψη′
No full textFirst evidence of the B 0 → J / ψ ω decay is found and the B s 0 → J / ψ η and B s 0 → J / ψ η ′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb -1 collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV. The branching fractions of these decays are measured relative to that of the B 0 → J / ψ ρ 0 decay:frac(B (B 0 → J / ψ ω), B (B 0 → J / ψ ρ 0)) = 0.89 ± 0.19 (stat) - 0.13 + 0.07 (syst),frac(B (B s 0 → J / ψ η), B (B 0 → J / ψ ρ 0)) = 14.0 ± 1.2 (stat) - 1.5 + 1.1 (syst) - 1.0 + 1.1 (frac(f d, f s)),frac(B (B s 0 → J / ψ η ′), B (B 0 → J / ψ ρ 0)) = 12.7 ± 1.1 (stat) - 1.3 + 0.5 (syst) - 0.9 + 1.0 (frac(f d, f s)), where the last uncertainty is due to the knowledge of f d / f s, the ratio of b-quark hadronization factors that accounts for the different production rate of B 0 and B s 0 mesons. The ratio of the branching fractions of B s 0 → J / ψ η ′ and B s 0 → J / ψ η decays is measured to befrac(B (B s 0 → J / ψ η ′), B (B s 0 → J / ψ η)) = 0.90 ± 0.09 (stat) - 0.02 + 0.06 (syst)
Navigating to the Moon along low-energy transfers
No full textThis paper presents a navigation strategy to fly to the Moon along a Weak Stability Boundary transfer trajectory. A particular strategy is devised to ensure capture into an uncontrolled relatively stable orbit at the Moon. Both uncertainty in the orbit determination process and in the control of the thrust vector are included in the navigation analysis. The orbit determination process is based on the definition of an optimal filtering technique that is able to meet accuracy requirements at an acceptable computational cost. Three sequential filtering techniques are analysed: an extended Kalman filter, an unscented Kalman filter and a Kalman filter based on high order expansions. The analysis shows that only the unscented Kalman filter meets the accuracy requirements at an acceptable computational cost. This paper demonstrates lunar weak capture for all trajectories within a capture corridor defined by all the trajectories in the neighbourhood of the nominal one, in state space. A minimum Delta v strategy is presented to extend the lifetime of the spacecraft around the Moon. The orbit determination and navigation strategies are applied to the case of the European Student Moon Orbiter
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
J. R. Arnold: Taking Science to the Moon: Lunar Experiments and the Apollo Program by D. A. Beattie
No full textJ. R. Arnold: Taking Science to the Moon: Lunar Experiments and the Apollo Program by D. A. Beattie
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
Digital Lunar Orbiter photographic atlas of the Moon
No full textThe digital Lunar Orbiter Atlas of the Moon is a reproduction of the 675 plates contained in Bowker and Hughes. The digital archive, however, offers many improvements upon its original hardbound predecessor. Multiple search capabilities were added to the database to expedite locating images and features of interest. For accuracy and usability, surface feature information has been updated and improved. Lastly, to aid in feature identification, a companion image containing feature annotation has been included.edited by Jeffrey J. Gillis ; foreword by Paul D. Spudi
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
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 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
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