Local Knowledge and Natural Resource Management in a Peasant Farming Community Facing Rapid Change: A Critical Examination

Environmental degradation is a major global problem, and addressing it is a key Millennium Development Goal. Its impacts are not just environmental (e.g., species loss), but also economic (e.g., reduced agricultural productivity), with degradation increasingly cited as a key cause of rural poverty in the developing world. The degradation literature typically emphasises common property or 'open access' natural resources, and how perverse incentives or missing institutions lead optimising private actors to degrade them. By contrast, the present paper considers degradation occurring on private farms in peasant communities. This is a critical yet delicate issue, given the poverty of such areas and questions about the role of farmers in either degrading or regenerating rural lands The paper examines natural resource management by peasant farmers in rural Tanzania. Its key concern is how the local knowledge informing farmers' management decisions adapts to challenges associated with environmental degradation and market liberalisation. Given their poverty, this question could have direct implications for the capacity of households to successfully meet their livelihood needs. Based on fresh empirical data, the paper finds that differential farmer knowledge helps explain the large differences in how households and communities respond to the degradation challenge. The implication is that some farmers adapt more effectively to emerging challenges than others, despite all being rational, optimising agents who follow the management strategies they deem best. The paper thus provides a critique of local knowledge, implying that some farmers experience adaptation slippages while others race ahead with effective adaptations. The paper speaks to the chronic poverty that plagues many rural communities in the developing world. Specifically, it helps explain the failure of proven 'sustainable agriculture' technologies to disseminate readily beyond an initial group of early innovators, and suggests a means to help 'scale up' local successes. Its key policy implication is to inform improved capacity building for peasant communities.

Displaced solar sail orbits : dynamics and applications

We consider 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. Prior results have been developed by using an optimal choice of the sail pitch angle, which maximises the out-of-plane displacement. In this paper we will use solar sail propulsion to provide station-keeping at periodic orbits around the libration points using small variations in the sail's orientation. 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. Applications include continuous line-of-sight communications with the lunar poles

On the stability of displaced two-body lunar orbits

In a prior study, a methodology was developed for computing approximate large displaced orbits in the Earth-Moon circular restricted three-body problem (CRTBP)by the Moon-Sail two-body problem. It was found that far from the L1 and L2 points, the approximate two-body analysis for large accelerations matches well with the dynamics of displaced orbits in relation to the three-body problem. In the present study, the linear stability characteristics of the families of approximate periodic orbits are investigated

Analysis and control of displaced periodic orbits in the Earth-Moon system

We consider 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. In this paper we will use solar sail propulsion to provide station-keeping at periodic orbits above the L2 point. We start by generating a reference trajectory about the libration points. 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. Because of the instability of the collinear libration points, orbit control is needed for a spacecraft to remian in the vicinity of these points. The reference trajectory is then tracked using a linear Quadratic Regulator (LQR). Finally, simulations are given to validate the control strategy. 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

Solar sail orbits at the Earth-Moon libration points

Solar sail technology offers new capabilities for the analysis and design of space missions. This new concept promises to be useful in overcoming the challenges of moving throughout the solar system. In this paper, novel families of highly non-Keplerian orbits for solar sail spacecraft at linear order are investigated in the Earth-Moon circular restricted three body problem, where the third body is a solar sail. In particular, periodic orbits near the collinear libration points in the Earth-Moon system will be explored along with their applications. The dynamics are completely different from the Earth-Sun system in that the Sun line direction constantly changes in the rotating frame but rotates once per synodic lunar month. Using an approximate, first order analytical solution to the nonlinear nonautonomous ordinary differential equations, periodic orbits can be constructed that are displaced above the plane of the restricted three-body system. This new family of orbits have the property of ensuring visibility of both the lunar far-side and the equatorial regions of the Earth, and can enable new ways of performing lunar telecommunications

Optical and X-ray Studies of Ten X-ray Selected Cataclysmic Binaries

We report on ground-based optical observations of ten cataclysmic binaries that were discovered through their X-ray emission. Time-resolved radial velocity spectroscopy yields unambiguous orbital periods for eight objects and ambiguous results for the remaining two. The orbital periods range from 87 min to 9.38 hr. We also obtained time-series optical photometry for six targets, four of which have coherent pulsations. These periods are 1218 s for 1RXS J045707.4+452751, 628 s for AX J1740.2-2903, 477 s for AX J1853.3-0128, and 935 s for IGR J19267+1325. A total of seven of the sources have coherent oscillations in X-rays or optical, indicating that they are intermediate polars (DQ Herculis stars). Time-resolved spectroscopy of one object, Swift J2218.4+1925, shows that it is an AM Herculis star, or polar, and IGR J19552+0044 may also be in that class. For another object, Swift J0476.2-1611, we find an orbital period of 9.384 hr and detect the spectrum of the secondary star. The secondary's spectral contribution implies a distance of 900 (+190, -150) pc, where the error bars are estimated using a Monte Carlo technique to account for correlated uncertainties.Comment: Accepted for publication in The Astronomical Journal. 38 pages, 16 figures Revised to include a correct finding chart for RX J0457+4

Displaced periodic orbits with low-thrust propulsion

Solar sailing and solar electric technology provide alternative forms of spacecraft propulsion. These propulsion systems can enable exciting new space-science mission concepts such as solar system exploration and deep space observation. The aim of this work is to investigate new families of highly non-Keplerian orbits, within the frame of the Earth-Moon circular restricted three-body problem (CRTBP), where the third massless body utilizes a hybrid of solar sail and a solar electric thruster. The augmented thrust acceleration is applied to ensure a constant displacement periodic orbit above L2, leading to simpler tracking from the lunar surface for communication applications. Using an approximate, first order analytical solution to the nonlinear non-autonomous ordinary differential equations, periodic orbits can be derived that are displaced above/below the plane of the CRTBP

Solar sail trajectories at the Earth-Moon Lagrange points

Paper 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

Potential Effects of a Realistic Solar Sail and Comparison to an Ideal Sail

Solar sail technology offers new capabilities for space missions due to the opportunities for non-Keplerian orbits. In this paper, novel families of highly non-Keplerian orbits for spacecraft utilising solar sail at linear order are investigated in the Earth-Moon circular restricted three-body problem. Firstly, it is assumed implicitly that the solar sail is a perfect reflector. Based upon the first-order approximation, an analytical formulation of the periodic orbits at linear order is presented. The approximate analytical solutions offer useful insights into the nature of the motion in the vicinity of the libration points, and are used to give periodic solutions numerically in the full nonlinear system. These orbits were accomplished by using an optimal choice of the sail pitch angle, which maximize the out-of-plane distance. Thereafter, the resulting effects of the non-ideal flat sail model have been computed and compared with an ideal solar sail. A square sail configuration, which is likely to be chosen for various near-term sail missions is used to illustrate the concept. The main effect of the non-perfect sail is to reduce the out-of-plane displacement distance which may be achieved for a given characteristic acceleration. It is also observed that there is a significant deviation in force magnitude between the realistic solar sail and the ideal solar sail model

Optical Counterparts of Two Fermi Millisecond Pulsars: PSR J1301+0833 and PSR J1628-3205

Using the 1.3m and 2.4m telescopes of the MDM Observatory, we identified the close companions of two eclipsing millisecond radio pulsars discovered by the Green Bank Telescope in searches of Fermi Gamma-ray Space Telescope sources, and measured their light curves. PSR J1301+0833 is a black widow pulsar in a 6.5 hr orbit whose companion star is strongly heated on the side facing the pulsar. It varies from R = 21.8 to R > 24 around the orbit. PSR J1628-3205 is a "redback," a nearly Roche-lobe filling system in a 5.0 hr orbit whose optical modulation in the range 19.0 < R < 19.4 is dominated by strong ellipsoidal variations, indicating a large orbital inclination angle. PSR J1628-3205 also shows evidence for a long-term variation of about 0.2 mag, and an asymmetric temperature distribution possibly due to either off-center heating by the pulsar wind, or large starspots. Modelling of its light curve restricts the inclination angle to i > 55 degrees, the mass of the companion to 0.16 < M_c < 0.30 M_sun, and the effective temperature to 3560 < T_eff < 4670 K. As is the case for several redbacks, the companion of PSR J1628-3205 is less dense and hotter than a main-sequence star of the same mass.Comment: 9 pages, 5 figures, accepted for publication in Ap