RPC-MAG The Fluxgate Magnetometer in the ROSETTA Plasma Consortium

The fluxgate magnetometer experiment onboard the ROSETTA spacecraft aims to measure the magnetic field in the interaction region of the solar wind plasma with comet 67P/Churyumov-Gerasimenko. It consists of a system of two ultra light (about 28 g each ) triaxial fluxgate magnetometer sensors, mounted on the 1.5 m long spacecraft boom. The measurement range of each sensor is ±16384 nT with quantization steps of 31 pT. The magnetometer sensors are operated with a time resolution of up to 0.05 s, corresponding to a bandwidth of 0–10 Hz. This performance of the RPC-MAG sensors allows detailed analyses of magnetic field variations in the cometary environment. RPC-MAG furthermore is designed to study possible remnant magnetic fields of the nucleus, measurements which will be done in close cooperation with the ROSETTA lander magnetometer experiment ROMAP.     

Laser measurements to space debris from Graz SLR station

In order to test laser ranging possibilities to space debris objects, the Satellite Laser Ranging (SLR) Station Graz installed a frequency doubled Nd:YAG pulse laser with a 1 kHz repetition rate, a pulse width of 10 ns, and a pulse energy of 25 mJ at 532 nm (on loan from German Aerospace Center Stuttgart – DLR). We developed and built low-noise single-photon detection units to enable laser ranging to targets with inaccurate orbit predictions, and adapted our standard SLR software to include a few hundred space debris targets. With this configuration, we successfully tracked – within 13 early-evening sessions of each about 1.5 h – 85 passes of 43 different space debris targets, in distances between 600 km and up to more than 2500 km, with radar cross sections from >15 m² down to <0.3 m², and measured their distances with an average precision of about 0.7 m RMS.     

韧性裂纹扩展的损伤力学描述

描述了基于材料微观空穴成核、长大和聚合的损伤力学模型,用增量本构关系模拟了空穴的成核和长大。用有限元损伤模型计算了裂纹的扩展,其计算值与试验结果吻合较好     

Software assisted authoring and viewing of ISS crew procedures

The European Space Agency (ESA) initiated a joint project with the National Aeronautics and Space Administration (NASA) and industry partners for improved authoring and execution of Operations Data File (ODF) procedures. The system consists of an authoring tool and a viewer. The authoring tool is currently used by NASA and ESA to write/convert ODF procedures. The viewer will be used onboard the International Space Station (ISS) starting from Flight Increment 11. The new system, thanks to its interaction capability, will help astronauts and operators in the execution of checklist and logic flow procedures that ensure precise performance of experiments and smooth operation of the various systems.     

The Cassini Ultraviolet Imaging Spectrograph Investigation

The Cassini Ultraviolet Imaging Spectrograph (UVIS) is part of the remote sensing payload of the Cassini orbiter spacecraft. UVIS has two spectrographic channels that provide images and spectra covering the ranges from 56 to 118 nm and 110 to 190 nm. A third optical path with a solar blind CsI photocathode is used for high signal-to-noise-ratio stellar occultations by rings and atmospheres. A separate Hydrogen Deuterium Absorption Cell measures the relative abundance of deuterium and hydrogen from their Lyman-α emission. The UVIS science objectives include investigation of the chemistry, aerosols, clouds, and energy balance of the Titan and Saturn atmospheres; neutrals in the Saturn magnetosphere; the deuterium-to-hydrogen (D/H) ratio for Titan and Saturn; icy satellite surface properties; and the structure and evolution of Saturn’s rings.This revised version was published online in July 2005 with a corrected cover date.     

Hybrid life support systems with integrated fuel cells and photobioreactors for a lunar base

The development of regenerative and sustainable life support systems (LSS) is a basic prerequisite to realize human long-term habitation in space. An efficient and reliable LSS is of high importance for assembling a future research base on the Moon and for further human space exploration missions beyond Low Earth Orbit. Because of longer distance to Earth and longer transfer times new requirements appear for LSS operation and functionality in comparison to the International Space Station. The minimization of resupply mass is a crucial factor to cope with this challenge. Regenerating the main media oxygen, water, and carbon as well as demonstrating a closed loop are essential milestones for an efficient and sustainable LSS. The logical step between partly regenerative physico-chemical and bioregenerative LSS is a so-called hybrid LSS characterized by the crosslinked integration of physico-chemical and simple biological system components.The Institute of Space Systems of the University of Stuttgart (IRS), the Institute of Technical Thermodynamics (ITT) of the German Aerospace Centre (DLR) and the Fraunhofer-Institute for Interfacial Engineering and Biotechnology (IGB) work together in a project on advanced LSS research and development. The IRS will investigate the integration of a photobioreactor (PBR) for algae cultivation as biological component and a reversible proton exchange membrane fuel cell (PEFC) as physico-chemical component into an LSS. Algae in the PBR absorb the carbon dioxide exhaled by the crew and produce biomass (food) and oxygen under light influence. The oxygen can be directed either into the crew cabin or into the fuel cell for generating electricity. Vice versa the electrolysis process splits water (from the PBR or the fuel cell process) into oxygen and hydrogen used as energy storage or propellant. Main task at IRS is a feasibility study on the mentioned technologies, considering the capability of media and product regeneration as well as the ability of integration of the components into a system. Synergies, mass reduction, dissimilar redundancy, and safety enhancement must be taken into account in order to specify integration problems and filtration costs. The IGB supports this study by its expertise in PBR operation, algae cultivation, and algae species selection. The ITT investigates the coupling of the PBR with three different fuel cell types: namely PEFC, SOFC (Solid Oxide Fuel Cell), and AFC (Alkaline Fuel Cell) under electrochemical performance aspects. The influence of PBR products on performance and lifetime of the different fuel cells is of high interest. The potential of potable water and electrical power supply is considered.     

Space Debris Mitigation in France,Germany, Italy and United Kingdom

The Space systems today provide growing benefits to enhance the quality of humankind. However, as a by-product, the orbiting objects inevitably leaves some debris which after 50 years of space activities represent a concern for all space agencies and manufacturers and operators. Since last year no international agreement was in place to mitigate the growing population of space debris objects. The successful result obtained at UN-COPUOS in 2007 and available in the OOSA web site, now gives to the public, a set of voluntary international guidelines that could, if adopted by each space fairing Country, help in maintaining the present space environment. More further steps are necessary in the future to define a legal and normative framework. The paper will present the seven established UN Space Debris guidelines as well as examples of the minimum steps to be carried out at national level to enable the UN-COPUOS to start the discussion of the legal aspect associated with the space debris issue.     

Cancer risk above 1 Gy and the impact for space radiation protection

Analyses of the epidemiological data on the Japanese A-bomb survivors, who were exposed to γ-rays and neutrons, provide most current information on the dose–response of radiation-induced cancer. Since the dose span of main interest is usually between 0 and 1 Gy, for radiation protection purposes, the analysis of the A-bomb survivors is often focused on this range. However, estimates of cancer risk for doses larger than 1 Gy are becoming more important for long-term manned space missions. Therefore in this work, emphasis is placed on doses larger than 1 Gy with respect to radiation-induced solid cancer and leukemia mortality. The present analysis of the A-bomb survivors data was extended by including two extra high-dose categories and applying organ-averaged dose instead of the colon-weighted dose. In addition, since there are some recent indications for a high neutron dose contribution, the data were fitted separately for three different values for the relative biological effectiveness (RBE) of the neutrons (10, 35 and 100) and a variable RBE as a function of dose. The data were fitted using a linear and a linear-exponential dose–response relationship using a dose and dose-rate effectiveness factor (DDREF) of both one and two. The work presented here implies that the use of organ-averaged dose, a dose-dependent neutron RBE and the bending-over of the dose–response relationship for radiation-induced cancer could result in a reduction of radiation risk by around 50% above 1 Gy. This could impact radiation risk estimates for space crews on long-term mission above 500 days who might be exposed to doses above 1 Gy. The consequence of using a DDREF of one instead of two increases cancer risk by about 40% and would therefore balance the risk decrease described above.     

Space tourism - A promising future?

Based on presentations made at the first International Symposium on Space Tourism (ISST), held in Bremen on March 20–22 1997, an overview over the current state of discussion on space tourism is given. Starting with an evaluation of the current situation for spaceflight, the author's viewpoint on the rationale for space tourism is described. The potential of space tourism as a future large space market is demonstrated using the results of recent market research and projection. This is followed by discussion of the appropriate technical means for space tourism in terms of space transportation systems and orbital infra-structure. In addition, the necessary non-technical boundary conditions to initiate space tourism and the associated dangers and risks are described and assessed