Ground-based calibration of the TAUVEX flight model

We describe in detail the procedures used for the ground testing and calibration of the flight model of the TAUVEX space telescope. We present the measurements done for this purpose, the various assumptions adopted during the ground calibration process, the results obtained, and provide a first approximation to the real performance of the experiment. The results of the ground-based calibration are that the system complies with the predicted performance in all aspects except for the total throughput, which is a factor of ∼5 smaller than expected. However, the instrument sensitivity measurement is highly uncertain due to known limitations of the available equipment and a more accurate calibration will be performed in orbit.     

Collisional timing of asteroids space weathering: A first approach

The space weathering, i.e. the evolution of surface properties over time, due to the exposure to external factors, has been shown to affect the optical properties of the asteroids, usually causing reddening (an effect which is measured in terms of the spectral slope in the visible and near infrared range) and darkening over time. However, some problems remain open. In particular, the timescale for reddening, which we estimate from laboratory experiments, is shorter—maybe, by two or even more orders of magnitude—than the typical asteroidal ages. Thus we should expect a complete saturation of the reddening effects for most of the objects, which does not happen, instead of a general significant dependence of the slope on the age, as indeed we find.In this paper we discuss, with the aid of a simplified model, how the collisions may affect the timing of the reddening process. We show that the collisions might halt the reddening, unless a significant reaccumulation of the fragments created in the cratering collisions takes place. In this case the timing for the complete reddening is driven by the collisional events, thus providing a rationale for the observed slope-age and slope-exposure relations.     

The Effect of GPS Ephemeris on the Accuracy of Precise Orbit Determination of LEO Satellite-borne GPS

The satellite-borne GPS receivers dedicated to precise orbit determination are now being carried by more and more low earth orbit (LEO) satellites and the satellite-borne GPS has become one of the main means for the precise orbit determination of low earth orbit satellites. The accuracy of satellite-borne GPS precise orbit determination depends on the accuracies of the GPS ephemeris and the clock error. Based on the orbit determination function of SHORDEIII zero-difference dynamics and using the observational data obtained by the GRACE satellites for the week from 2005 August 1 to 7 as an example, three versions of GPS ephemerides (igs, igr and igu) are used to carry out orbit determination under the same conditions and to estimate the effect of the GPS ephemeris accuracy on the accuracy of orbit determination of low earth orbit satellites. Our calculated results show that the two ephemerides, igs and igr, are equivalent to each other in orbit determination accuracy (about 9.5 cm), while igu is slightly less accurate, at about 10.5 cm. The effect produced by the data of the high frequency GPS satellite clock error on the accuracy of orbit determination is 1–6 cm.     

PEGASE, an infrared interferometer to study stellar environments and low mass companions around nearby stars

PEGASE is a mission dedicated to the exploration of the environment (including habitable zone) of young and solar-type stars (particularly those in the DARWIN catalogue) and the observation of low mass companions around nearby stars. It is a space interferometer project composed of three free flying spacecraft, respectively featuring two 40 cm siderostats and a beam combiner working in the visible and near infrared. It has been proposed to ESA as an answer to the first “Cosmic Vision” call for proposals, as an M mission. The concept also enables full-scale demonstration of space nulling interferometry operation for DARWIN.

Cross-scale: multi-scale coupling in space plasmas

Most of the visible universe is in the highly ionised plasma state, and most of that plasma is collision-free. Three physical phenomena are responsible for nearly all of the processes that accelerate particles, transport material and energy, and mediate flows in systems as diverse as radio galaxy jets and supernovae explosions through to solar flares and planetary magnetospheres. These processes in turn result from the coupling amongst phenomena at macroscopic fluid scales, smaller ion scales, and down to electron scales. Cross-Scale, in concert with its sister mission SCOPE (to be provided by the Japan Aerospace Exploration Agency—JAXA), is dedicated to quantifying that nonlinear, time-varying coupling via the simultaneous in-situ observations of space plasmas performed by a fleet of 12 spacecraft in near-Earth orbit. Cross-Scale has been selected for the Assessment Phase of Cosmic Vision by the European Space Agency.      

Mars environment and magnetic orbiter model payload

Mars Environment and Magnetic Orbiter was proposed as an answer to the Cosmic Vision Call of Opportunity as a M-class mission. The MEMO mission is designed to study the strong interconnections between the planetary interior, atmosphere and solar conditions essential to understand planetary evolution, the appearance of life and its sustainability. MEMO provides a high-resolution, complete, mapping of the magnetic field (below an altitude of about 250 km), with an yet unachieved full global coverage. This is combined with an in situ characterization of the high atmosphere and remote sensing of the middle and lower atmospheres, with an unmatched accuracy. These measurements are completed by an improved detection of the gravity field signatures associated with carbon dioxide cycle and to the tidal deformation. In addition the solar wind, solar EUV/UV and energetic particle fluxes are simultaneously and continuously monitored. The challenging scientific objectives of the MEMO mission proposal are fulfilled with the appropriate scientific instruments and orbit strategy. MEMO is composed of a main platform, placed on a elliptical (130 × 1,000 km), non polar (77° inclination) orbit, and of an independent, higher apoapsis (10,000 km) and low periapsis (300 km) micro-satellite. These orbital parameters are designed so that the scientific return of MEMO is maximized, in terms of measurement altitude, local time, season and geographical coverage. MEMO carry several suites of instruments, made of an ‘exospheric-upper atmosphere’ package, a ‘magnetic field’ package, and a ‘low-middle atmosphere’ package. Nominal mission duration is one Martian year.     

Results from the Huygens probe on Titan

The Cassini–Huygens mission, comprising the NASA Saturn Orbiter and the ESA Huygens Probe, arrived at Saturn in late June 2004. The Huygens probe descended under parachute in Titan’s atmosphere on 14 January 2005, 3 weeks after separation from the Orbiter. We discuss here the breakthroughs that the Huygens probe, in conjunction with the Cassini spacecraft, brought to Titan science. We review the achievements ESA’s Huygens probe put forward and the context in which it operated. The findings include new localized information on several aspects of Titan science: the atmospheric structure and chemical composition; the aerosols distribution and content; the surface morphology and composition at the probe’s landing site; the winds, the electrical properties, and the implications on the origin and evolution of the satellite.     

空间大地测量技术对确定地面坐标框架、地形变与地球重力场的贡献和进展--出席2005年国际大地测量协会(IAG) 科学大会札记

国际大地测量协会（IAG）科学大会于2005年8月22~26日在澳大利亚凯尔斯（Cairns）召开。会议名称为“动力行星2005”（Dynamic Planet 2005）。会议就有关完善全球和地区性地面坐标参考框架、卫星重力测量在确定地球重力场时空分辨率、开展航空激光和雷达成像及其干涉技术在地形变和灾害监测,以及对大气的研究、建立和完善全球大地测量观测系统(GGOS)、开展行星大地测量的研究等方面的内容做了广泛的学术交流,内容比较丰富。     

昆明盆地北部浅层地下水硝酸盐污染分析

研究认为东部浅层地下水的污染比较严重,硝酸盐超标率达到了88％;在靠近湖滨平原区地下水硝酸盐为中等污染,其超标率在（30．77～66．67）％之间。时间上,研究区随着土地利用的变化,地下水硝酸盐污染在最近几年在逐渐趋向减轻。     

Translocal assemblages: Space, power and social movements

In this paper, I deploy an analytic of ‘translocal assemblage’ as a means for conceptualising space and power in social movements. I offer a relational topology that is open to how actors within movements construct different spatial imaginaries and practices in their work. In using the prefix ‘translocal’, I am signifying three orientations. First, translocal assemblages are composites of place-based social movements which exchange ideas, knowledge, practices, materials and resources across sites. Second, assemblage is an attempt to emphasise that translocal social movements are more than just the connections between sites. Sites in translocal assemblages have more depth than the notion of ‘node’ or ‘point’ suggests – as connoted by network – in terms of their histories, the labour required to produce them, and their inevitable capacity to exceed the connections between other groups or places in the movement. Third, they are not simply a spatial category, output, or resultant formation, but signify doing, performance and events. I examine the potential of assemblage to offer an alternative account to that of the ‘network’, the predominant and often de facto concept used in discussions of the spatiality of social movements. I draw on examples from one particular translocal assemblage based in and beyond Mumbai which campaigns on housing within informal settlements: Slum/Shack Dwellers International.