Mars mission concepts and opportunities

Trajectory and mission requirement data are presented for Earth Mars opposition and conjunction class roundtrip flyby and stopover mission opportunities available between 1997 and 2045. The opposition class flyby mission uses direct transfer trajectories to and on return from Mars. The opposition class stopover mission employs the gravitational field of Venus to accelerate the space vehicle on either the outbound or inbound leg in order to reduce the propulsion requirement associated with the opposition class mission. The conjunction class mission minimizes propulsion requirements by optimizing the stopover time at Mars

A Parameterisation of Algorithms for Distributed Constraint Optimisation via Potential Games

This paper introduces a parameterisation of learning algorithms for distributed constraint optimisation problems (DCOPs). This parameterisation encompasses many algorithms developed in both the computer science and game theory literatures. It is built on our insight that when formulated as noncooperative games, DCOPs form a subset of the class of potential games. This result allows us to prove convergence properties of algorithms developed in the computer science literature using game theoretic methods. Furthermore, our parameterisation can assist system designers by making the pros and cons of, and the synergies between, the various DCOP algorithm components clear

Climate Choices: How Should We Meet the Challenges of a Warming Planet?

This issue guide was prepared for the National Issues Forums Institute in collaboration with the Kettering Foundation and the North American Association for Environmental Education. The Environment and Society Series is designed to promote meaningful, productive deliberation, convened locally and online, about difficult issues that affect the environment and communities.All around is evidence that the climate is changing. Summers are starting earlier and lasting longer. Heat waves are becoming more frequent and intense. Dry regions are getting drier and wet regions are seeing heavier rains. Record cold and snowfalls blanket some parts of the country, while record fires ravage forests across the West.The effects are being felt across many parts of the United States. Farmworkers in California's Central Valley, snow-weary New England business owners, crab fishermen in Alaska, and cattle ranchers across the Great Plains have all seen uncommon and extreme weather. Occasional odd weather and weather cycles are nothing unusual.But the more extreme and unpredictable weather being experienced around the world points to dramatic changes in climate -- the conditions that take place over years, decades, and longer.Climate disruptions have some people worried about their health, their children, their homes, their livelihoods, their communities, and even their personal safety. They wonder about the future of the natural areas they enjoy and the wild animals and plants that live there. In addition, there are growing concerns about our national security and how climate change might affect scarce resources around the planet and increase global tensions

The Thomson scattering cross section in a magnetized, high density plasma

We calculate the Thomson scattering cross section in a non-relativistic, magnetized, high density plasma -- in a regime where collective excitations can be described by magnetohydrodynamics. We show that, in addition to cyclotron resonances and an elastic peak, the cross section exhibits two pairs of peaks associated with slow and fast magnetosonic waves; by contrast, the cross section arising in pure hydrodynamics possesses just a single pair of Brillouin peaks. Both the position and the width of these magnetosonic-wave peaks depend on the ambient magnetic field and temperature, as well as transport and thermodynamic coefficients, and so can therefore serve as a diagnostic tool for plasma properties that are otherwise challenging to measure.Comment: Main paper: pp 1-8. Appendix: pp 8-10. 2 figure