The solar wind interaction with the geomagnetic field

A review is presented of the interaction of the solar wind with the magnetic field of the earth. The material is developed primarily from an observational point of view. The early observations are covered through late 1963, with primary emphasis on the sunward interaction region. The historical review of the early results is discussed in terms of the significant contributions of each satellite observation and in the light of our present concept of the solar wind-geomagnetic field interaction. Subsequent to 1963 the observations tend to overlap such that a strictly historical treatment is not tractable and the material is presented from a phenomenological approach. The daytime and night-time hemispheres are covered separately in terms of the significant and separable phenomena which dominate the structure and dynamics of these two regions. Satellite and deep space probe data are compared with relevant theory. Further observational eflorts needed to improve our understanding of the details of the solar wind-geomagnetic field interaction are also discussed.     

The future of Earth observations in the USA

Earth observations is a controversial subject because of the diversity of interests involved, but one that should not be ignored, as is currently the case, by the US government. This article describes the changing character of Earth observations and the opportunities it provides for economic benefit and national and international economies of scale. Such opportunities can best be met by the formation of an international Earth observations body, in which the USA, represented by an expanded EOSAT, should play a leading role.     

The optimal distribution of search effort: existence, uniquenessand the minimax solution

The detection search problem, one of distributing limited resources so as to maximize the detection probability in the single-try search for a concealed target with known probability density, is analyzed. Under fairly general assumptions, the optimal search density uniquely exists when the detection index is governed by the law of diminishing returns and another simple regularity condition. Numerical procedure based on the bisection method, which is guaranteed to converge if the solution uniquely exists, may be used to solve for the optimal search density and the associated Lagrange multiplier. When it is not possible to confidently estimate the target a priori probability density, the minimax solution guarantees a positive detection probability at the expense of degradation in performance     

The extravehicular mobility unit: A review of environment, requirements, and design changes in the US spacesuit

Requirements are rarely static, and are ever more likely to evolve as the development time of a system stretches out and its service life increases. In this paper, we discuss the evolution of requirements for the US spacesuit, the extravehicular mobility unit (EMU), as a case study to highlight the need for flexibility in system design. We explore one fundamental environmental change, using the Space Shuttle EMU aboard the International Space Station, and the resulting EMU requirement and design changes. The EMU, like other complex systems, faces considerable uncertainty during its service life. Changes in the technical, political, or economic environment cause changes in requirements, which in turn necessitate design modifications or upgrades. We make the case that flexibility is a key attribute that needs to be embedded in the design of long-lived, complex systems to enable them to efficiently meet the inevitability of changing requirements after they have been fielded.     

Buckling and post-buckling behavior of shallow supported cylindrical panels

The problem of the post-buckling behavior of the supported cylindrical panel under uniform axial compression is solved. The cylindrical supported panel is considered as a beam on the Winkler elastic foundation, the stiffness coefficient of which is calculated at the known value of buckling load. The criteria for post-buckling estimation are introduced, namely, vanishing of the determinant of the resolving system of equations and going to infinity of the deflection and strain energy in the implementation of post buckling. A good agreement of the post-buckling load obtained in this work with the experimental results is shown.     

Improved kHz-SLR tracking techniques and orbit quality analysis for LEO missions

Satellite gravity field missions such as CHAMP, GRACE and GOCE are designed as low Earth orbiting spacecraft (LEO) with orbit heights of about 250–500 km. The challenging mission objectives require a very precise knowledge of the satellite orbit position in space. For these missions precise orbit information is typically provided by GPS satellite-to-satellite tracking (SST) observations supported by satellite laser ranging (SLR).     

Cassini Radio Science

Cassini radio science investigations will be conducted both during the cruise (gravitational wave and conjunction experiments) and the Saturnian tour of the mission (atmospheric and ionospheric occultations, ring occultations, determinations of masses and gravity fields). New technologies in the construction of the instrument, which consists of a portion on-board the spacecraft and another portion on the ground, including the use of the Ka-band signal in addition to that of the S- and X-bands, open opportunities for important discoveries in each of the above scientific areas, due to increased accuracy, resolution, sensitivity, and dynamic range.This revised version was published online in July 2005 with a corrected cover date.