Simultaneous determination of aerosol- and surface characteristics from top-of-atmosphere reflectance using MERIS on board of ENVISAT

The determination of aerosol optical thickness (AOT) from nadir scanning multi-spectral radiometers, like SeaWiFS, MERIS or MODIS, requires the separation of spectral atmospheric and surface properties. Since SeaWiFS and MERIS do not provide information at 2.1 μm, like MODIS, the estimation of the surface reflectance cannot be made by the cross correlation approach described by Kaufman et al., 1997. The BAER approach (Bremen AErosol Retrieval), von Hoyningen-Huene et al., 2003, uses a linear mixing model of spectra for ‘green vegetation’ and ‘bare soil’, tuned by the NDVI, determining an apparent surface to enable this separation of aerosol and surface properties from VIS and NIR channels. Thus AOT can be derived over a wide range of land surfaces for wavelengths <0.67 μm. Using MERIS L1 data over Europe, the AOT retrieved is comparable with ground-based observations, provided by AERONET. Regional variation of AOT can be observed, showing the atmospheric variability for clear sky conditions by: large scale variation of aerosol turbidity, regional pollution, urban regions, effects of contrails and cases of aerosol-cloud interaction. Simultaneously with the spectral AOT also spectral surface reflectance is obtained, where all atmospheric influences have been considered (molecules, aerosols and absorbing gases (O₃)) for channels with wavelengths <0.67 μm. The AOT is extrapolated by Angström power law to NIR channels and the atmospheric correction for land surface properties is performed, enabling the further investigation of land use and spectral land properties.     

Adaptive Phased-Array Tracking in ECM using Negative Information

Target tracking with adaptive phased-array radars in the presence of standoff jamming presents both challenges and opportunities to the track filter designer. A measurement likelihood function is derived for this situation which accounts for the effect of both positive and negative contact information. This likelihood function is approximated a? a weighted sum of Gaussian terms consisting of both positive and negative weights, accounting for the positive and negative contact information. Additionally, recent theoretical results have been reported which have derived an accurate measurement error covariance in the vicinity of the jammer when adaptive beamforming is used by the radar to null the effects of the jammer. We compare the impact of using a likelihood function that accounts for negative contact information and the corrected measurement error covariance by comparing five Kalman filter-based trackers in five different scenarios. We show that only those track filters which use both the negative contact information and the corrected measurement error covariance are effective in maintaining track on a maneuvering target as it passes through the jamming region. This approach can also be generalized to any target tracking problem where the sensor response is anisotropic.     

Advanced data acquisition system for SEVAN

Huge magnetic clouds of plasma emitted by the Sun dominate intense geomagnetic storm occurrences and simultaneously they are correlated with variations of spectra of particles and nuclei in the interplanetary space, ranging from subtermal solar wind ions till GeV energy galactic cosmic rays. For a reliable and fast forecast of Space Weather world-wide networks of particle detectors are operated at different latitudes, longitudes, and altitudes. Based on a new type of hybrid particle detector developed in the context of the International Heliophysical Year (IHY 2007) at Aragats Space Environmental Center (ASEC) we start to prepare hardware and software for the first sites of Space Environmental Viewing and Analysis Network (SEVAN). In the paper the architecture of the newly developed data acquisition system for SEVAN is presented. We plan to run the SEVAN network under one-and-the-same data acquisition system, enabling fast integration of data for on-line analysis of Solar Flare Events. An Advanced Data Acquisition System (ADAS) is designed as a distributed network of uniform components connected by Web Services. Its main component is Unified Readout and Control Server (URCS) which controls the underlying electronics by means of detector specific drivers and makes a preliminary analysis of the on-line data. The lower level components of URCS are implemented in C and a fast binary representation is used for the data exchange with electronics. However, after preprocessing, the data are converted to a self-describing hybrid XML/Binary format. To achieve better reliability all URCS are running on embedded computers without disk and fans to avoid the limited lifetime of moving mechanical parts. The data storage is carried out by means of high performance servers working in parallel to provide data security. These servers are periodically inquiring the data from all URCS and storing it in a MySQL database. The implementation of the control interface is based on high level web standards and, therefore, all properties of the system can be remotely managed and monitored by the operators using web browsers. The advanced data acquisition system at ASEC in Armenia was started in November, 2006. The reliability of the multi-client service was proven by continuously monitoring neutral and charged cosmic ray particles. Seven particle monitors are located at 2000 and 3200 m above sea level at a distance of 40 and 60 km from the main data server.     

THE ELECTRON DRIFT INSTRUMENT FOR CLUSTER

The Electron Drift Instrument (EDI) measures the drift of a weak beam of test electrons that, when emitted in certain directions, return to the spacecraft after one or more gyrations. This drift is related to the electric field and the gradient in the magnetic field, and these quantities can, by use of different electron energies, be determined separately. As a by-product, the magnetic field strength is also measured. The present paper describes the scientific objectives, the experimental method, and the technical realization of the various elements of the instrument.     

Initial design of laboratories for sustainable habitation

An effective and self-sustainable artificial habitat design is essential for human spaceflight and expansion of mankind into orbit or towards other celestial bodies. There are two approaches that need to be implemented in future sustainable habitats: the use of re-cycling technologies in order to gain experience in closed-loop processes and the primary production of resource materials using In Situ Resource Utilisation (ISRU) principles. Various products will be provided and, where applicable, recycled in such a system taking into account basic human factors requirements such as crew work load capacity, safety and well-being, namely:     

The AWIATOR airborne LIDAR turbulence sensor

The development and first flight tests are described of a short pulse direct measuring UV LIDAR for the measurement of gusts, turbulence and potentially wake vortices. The results of these stage 1 tests confirm that relative wind velocities can be measured with a standard deviation of below 10 m/s even at high altitudes with no appreciable aerosol concentrations. Operating the system under various flight conditions including rain, dense clouds, and clear air up to 24,000 ft was highly successful. Means to push the standard deviation below 1.6 m/s, foremost by increasing the laser output power and the efficiency of the light collecting system, are identified and quantified. Questions of instrument stability are addressed.     

Automated payload and instruments for astrobiology research developed and studied by German medium-sized space industry in cooperation with European academia

For more than a decade Kayser-Threde, a medium-sized enterprise of the German space industry, has been involved in astrobiology research in partnership with a variety of scientific institutes from all over Europe. Previous projects include exobiology research platforms in low Earth orbit on retrievable carriers and onboard the Space Station. More recently, exobiology payloads for in situ experimentation on Mars have been studied by Kayser-Threde under ESA contracts, specifically the ExoMars Pasteur Payload. These studies included work on a sample preparation and distribution systems for Martian rock/regolith samples, instrument concepts such as Raman spectroscopy and a Life Marker Chip, advanced microscope systems as well as robotic tools for astrobiology missions. The status of the funded technical studies and major results are presented. The reported industrial work was funded by ESA and the German Aerospace Center (DLR).     

Study of waves in the magnetotail region with cluster and DSP

The study of the neutral sheet is of fundamental importance in understanding the dynamics of the Earth’s magnetosphere. From the earliest observation of the magnetotail, it has been found that the neutral sheet frequently appears to be in motion due to changing solar wind conditions and geomagnetic activity. Multiple crossings of the neutral sheet by spacecraft have been attributed to a flapping motion of the neutral sheet in the north–south direction, a wavy profile either along the magnetotail or the dawn–dusk direction. Cluster observations have revealed that the flapping motions of the Earth’s magnetotail are of internal origin and that kink-like waves are emitted from the central part of the tail and propagate toward the tail flanks. This flapping motion is shown here to propagate at an angle of ∼45° with x_GSM. A possible assumption that the flapping could be created by a wake travelling away from a fast flow in the current sheet is rejected. Other waves in the magnetotail are found in the ULF range. One conjunction event between Cluster and DoubleStar TC1 is presented where all spacecraft show ULF wave activity at a period of approximately 5 min during fast Earthward flow. These waves are shown to be Kelvin–Helmholtz waves on the boundaries of the flow channel. Calculations show that the conversion of flow energy into magnetic energy through the Kelvin–Helmholtz instability can contribute to a significant part of flow breaking between Cluster and DoubleStar TC1.     

The rapid neutron-capture process and the synthesis of heavy and neutron-rich elements

Recent developments in theoretical model-calculations for the synthesis of heavy and neutron-rich chemical elements by means of the rapid neutron-capture process are reviewed. Special emphasis is put on a discussion of possible astrophysical sites, e.g. supernova models, and extrapolated nuclear input data as well. Numerical methods to solve complex nuclear reaction-networks are presented.