Swan Observations of the Solar Wind Latitude Distribution and its Evolution Since Launch

SWAN is the first space instrument dedicated to the monitoring of the latitude distribution of the solar wind by the Lyman alpha method. The distribution of interstellar H atoms in the solar system is determined by their destruction during ionization charge-exchange with solar wind protons. Maps of sky Ly-α emission have been recorded regularly since launch. The upwind maximum emission region deviates strongly from the pattern that would be expected from a solar wind that is constant with latitude. It is divided in two lobes by a depression aligned with the solar equatorial plane, called the Lyman-alpha groove, due to enhanced ionization along the neutral sheet where the slow and dense solar wind is concentrated. The groove (or the anisotropy) is more pronounced in 1997 than in 1996, but it then decreases between 1997 and 1998. This revised version was published online in June 2006 with corrections to the Cover Date.     

Status and Perspectives in Protective Design

Starting with an introduction into the field of hypervelocity impacts, an overview over current research in the area of protection against space debris is given. Trends and strategies to further develop know-how in protection technology are then discussed. One purpose is to demonstrate that improvements in shield efficiency can be expected. To achieve this aim, a strategy is outlined which tries to avoid the adjustment of numerical and material parameters by fits to penetration experiments. Instead, it is suggested to determine material parameters from carefully selected laboratory tests, covering a broad range of strains, strain rates and stress states. Knowledge of the dynamic material behaviour can then be used for the development of new shield concepts by means of numerical simulation.     

The Rosetta Lander (“Philae”) Investigations

The paper describes the Rosetta Lander named Philae and introduces its complement of scientific instruments. Philae was launched aboard the European Space Agency Rosetta spacecraft on 02 March 2004 and is expected to land and operate on the nucleus of 67P/Churyumov-Gerasimenko at a distance of about 3 AU from the Sun. Its overall mass is ~98 kg (plus the support systems remaining on the Orbiter), including its scientific payload of ~27 kg. It will operate autonomously, using the Rosetta Orbiter as a communication relay to Earth. The scientific goals of its experiments focus on elemental, isotopic, molecular and mineralogical composition of the cometary material, the characterization of physical properties of the surface and subsurface material, the large-scale structure and the magnetic and plasma environment of the nucleus. In particular, surface and sub-surface samples will be acquired and sequentially analyzed by a suite of instruments. Measurements will be performed primarily during descent and along the first five days following touch-down. Philae is designed to also operate on a long time-scale, to monitor the evolution of the nucleus properties. Philae is a very integrated project at system, science and management levels, provided by an international consortium. The Philae experiments have the potential of providing unique scientific outcomes, complementing by in situ ground truth the Rosetta Orbiter investigations. Philae team members are listed in the acknowledgements     

Monitoring of Saharan dust over the Atlantic using Meteosat-VIS-data

The optical depth of Saharan dustclouds (a component of the radiation budget), which can be clearly seen in satellite images taken over the Atlantic, can be determined from the Meteosat VIS-data. ‘Favourable angles’ between sun, observed point and satellite are chosen so that the optical depth is determined with an inaccuracy of only about 20%.We present several clouds, their change over time, and some of their other interesting features. The results are discussed.     

A method for estimating cross radiance

When imaging the surface from satellites or aircraft, “cross radiance” diminishes the information content of the pictures. In this paper a simple method is presented to estimate the value of cross radiance. This method includes a height-dependent aerosol size distribution model and the calculations refer to the single scattering approximation. The height variation of aerosol size distribution has significant effect on the value of cross radiance, while the areal distribution does not change much in comparison with that of the height-independent aerosol model.     

STEREO Space Weather and the Space Weather Beacon

The Solar Terrestrial Relations Observatory (STEREO) is primarily a solar and interplanetary research mission, with one of the natural applications being in the area of space weather. The obvious potential for space weather applications is so great that NOAA has worked to incorporate the real-time data into their forecast center as much as possible. A subset of the STEREO data will be continuously downlinked in a real-time broadcast mode, called the Space Weather Beacon. Within the research community there has been considerable interest in conducting space weather related research with STEREO. Some of this research is geared towards making an immediate impact while other work is still very much in the research domain. There are many areas where STEREO might contribute and we cannot predict where all the successes will come. Here we discuss how STEREO will contribute to space weather and many of the specific research projects proposed to address STEREO space weather issues. The data which will be telemetered down in the Space Weather Beacon is also summarized here. Some of the lessons learned from integrating other NASA missions into the forecast center are presented. We also discuss some specific uses of the STEREO data in the NOAA Space Environment Center.