Arm end-point trajectories under normal and micro-gravity environments

The purpose of the present experiment was to study the way in which the CNS represents gravitational force during vertical arm pointing movements. Movements in upward and downward directions were executed by two cosmonauts in normal-gravity and weightlessness. Analyses focused upon finger kinematics in the sagittal plane. In normal-gravity, downward direction movements showed smaller curvatures and greater relative times to peak velocity (AT/MT) when compared with upward direction movements. Data from the weightlessness experiments showed that whilst downward movements decreased their curvature during space flight, curvatures of upward movements changed slightly. Furthermore, AT/MT was modified during the first days in micro-gravity for both directions, recovering, however, to pre-flight values after 18 days in space. Results from the present study, provide evidence that gravitational force is centrally treated constituting an important component of the motor plan for vertical arm movements.     

Biomass Production System (BPS) plant growth unit.

The Biomass Production System (BPS) was developed under the Small Business Innovative Research (SBIR) program to meet science, biotechnology and commercial plant growth needs in the Space Station era. The BPS is equivalent in size to a double middeck locker, but uses its own custom enclosure with a slide out structure to which internal components mount. The BPS contains four internal growth chambers, each with a growing volume of more than 4 liters. Each of the growth chambers has active nutrient delivery, and independent control of temperature, humidity, lighting, and CO2 set-points. Temperature control is achieved using a thermoelectric heat exchanger system. Humidity control is achieved using a heat exchanger with a porous interface which can both humidify and dehumidify. The control software utilizes fuzzy logic for nonlinear, coupled temperature and humidity control. The fluorescent lighting system can be dimmed to provide a range of light levels. CO2 levels are controlled by injecting pure CO2 to the system based on input from an infrared gas analyzer. The unit currently does not scrub CO2, but has been designed to accept scrubber cartridges. In addition to providing environmental control, a number of features are included to facilitate science. The BPS chambers are sealed to allow CO2 and water vapor exchange measurements. The plant chambers can be removed to allow manipulation or sampling of specimens, and each chamber has gas/fluid sample ports. A video camera is provided for each chamber, and frame-grabs and complete environmental data for all science and hardware system sensors are stored on an internal hard drive. Data files can also be transferred to 3.5-inch disks using the front panel disk drive.     

Concentration of ions in the topside ionosphere as measured onboard the <Emphasis Type=Italic>DEMETER</Emphasis> satellite: Morphology and dependence on solar and geomagnetic activity

Variations in concentration of ions H⁺, He⁺, and O⁺ are studied at a height of about 700 km using the data of continuous observations onboard the DEMETER satellite at the decline and in the minimum of solar activity from 2004 to 2008. Latitudinal distributions, seasonal behavior, and irregular variations in ion concentrations and their dependence on solar and geomagnetic activity are considered. Within this altitude range, for the first time an analysis is performed of the dataset of many-year continuous observations in both hemispheres from the equatorial to subauroral latitudes. This made it possible to describe the seasonal and irregular variations of the concentrations of main ion species with better time and spatial resolution than in the available empirical models. The dependence of concentrations of three types of ions on solar and geomagnetic activity is studied at time scales from several days to several years, and it is shown that the anti-phase change in concentrations of O⁺ and light ions known from publications is partly a result of mutual dependence of solar and geomagnetic activity and is observed only at time scales beginning from several months. At time scales from several days to several weeks, variations in the concentration of O⁺ and light ions are governed mainly by solar and geomagnetic activity, respectively.     

Orbit determination for the GOCE satellite

Precise Orbit Determination (POD) for the Gravity field and steady-state Ocean Circulation Explorer (GOCE), the first core explorer mission by the European Space Agency (ESA), forms an integrated part of the so-called High-Level Processing Facility (HPF). Two POD chains have been set up referred to as quick-look Rapid and Precise Science Orbit determination or RSO and PSO, respectively. These chains make use of different software systems and have latencies of 1 day and 2 weeks, respectively, after tracking data availability. The RSO and PSO solutions have to meet a 3-dimensional (3D) position precision requirement of 50 cm and a few cm, respectively. The tracking data will be collected by the new Lagrange GPS receiver and the predicted characteristics of this receiver have been taken into account during the implementation phase of the two chains.     

Linkage of the ionospheric peak electron density and height deduced from the topside sounding data

Topside sounding electron density profiles are analyzed to explore interrelations of the F2 layer critical frequency and the peak height for a representative set of conditions provided by ISIS1, ISIS2, IK19 and Cosmos-1809 satellites for the period of 1969–1987. The foF2 and hmF2 are delivered with exponential extrapolation of electron density profile to zero of its 1st derivative. It is shown that the linear regression exists between foF2 and hmF2 under different conditions. The linkage between the two parameters amended to the empirical model of the peak height [Gulyaeva, T.L., Bradley, P.A., Stanislawska, I., Juchnikowski, G. Towards a new reference model of hmF2 for IRI. Adv. Space Res. 42, 666–672, doi:10.1016/j.asr.2008.02.021, 2008] results in an empirical model of the both foF2 and hmF2 expressed by superposition of functions in terms of local-time, season, geodetic longitude, modified dip latitude and solar activity. For the solar activity we use a proxy Fsp index averaged from the mean solar radio flux F10.7s for the past 81 days (3 solar rotations) and F10.7 value for 1 day prior the day of observation. Impact of geomagnetic activity is not discernible with the topside sounding data due to mixed positive and negative storm-time effects. Appreciable differences have been revealed between IRI-CCIR predictions and outcome of the new model which might be attributed to the different techniques of the peak electron density and height derivation, different epochs and different global distribution of the source data as well as the different mathematical functions involved in the maps and the model presentation.     

Laboratory calibration measurements of a piezoelectric lead zirconate titanate cosmic dust detector at low velocities

A cosmic dust monitor for use onboard a spacecraft is currently being developed using a piezoelectric lead zirconate titanate element (PZT). Its characteristics of the PZT sensor is studied by ground-based laboratory impact experiments using hypervelocity particles supplied by a Van de Graaff accelerator. The output signals obtained from the sensor just after the impact appeared to have a waveform that was explicitly related to the particle’s impact velocity. For velocities less than ∼6 km/s, the signal showed an oscillation pattern and the amplitude was proportional to the momentum of the impacting particle. For higher velocities, the signal gradually changed to a single waveform. The rise time of this single waveform was proportional to the particle’s velocity for velocities above ∼6 km/s. The present paper reports on results for the low velocity case and especially discusses the effect of an outer coating of the sensor with a paint, which is used to reduce heating by solar radiation.     

Hybrid simulations of the O ion escape from Venus: Influence of the solar wind density and the IMF x component

As an initial effort to study the evolution of the Venus atmosphere, the influence of the solar wind density and the interplanetary magnetic field (IMF) x component (the x-axis points from Venus towards the Sun) on the O⁺ ion escape rate from Venus is investigated using a three-dimensional quasi-neutral hybrid (HYB-Venus) model. The HYB-Venus model is first applied to a case of the high-density (100 cm⁻³) solar wind interaction with Venus selected from the Pioneer Venus Orbiter observations to demonstrate its capability for the study. Two sets of simulations with a wide range of solar wind densities and different IMF x components are then performed. It is found that the O⁺ ion escape rate increases with increasing solar wind density. The O⁺ ion escape rate saturates when the solar wind density becomes high (above 100 cm⁻³). The results also suggest that the IMF x component enhances the O⁺ ion escape rate, given a fixed IMF component perpendicular to the x-axis. Finally, the results imply a higher ion loss rate for early-Venus, when solar conditions were dramatically different.     

Surface temperature estimation in Singhbhum Shear Zone of India using Landsat-7 ETM+ thermal infrared data

Land surface temperature (LST) is an important factor in global change studies, heat balance and as control for climate change. A comparative study of LST over parts of the Singhbhum Shear Zone in India was undertaken using various emissivity and temperature retrieval algorithms applied on visible and near infrared (VNIR), and thermal infrared (TIR) bands of high resolution Landsat-7 ETM+ imagery. LST results obtained from satellite data of October 26, 2001 and November 2, 2001 through various algorithms were validated with ground measurements collected during satellite overpass. In addition, LST products of MODIS and ASTER were compared with Landsat-7 ETM+ and ground truth data to explore the possibility of using multi-sensor approach in LST monitoring. An image-based dark object subtraction (DOS3) algorithm, which is yet to be tested for LST retrieval, was applied on VNIR bands to obtain atmospheric corrected surface reflectance images. Normalized difference vegetation index (NDVI) was estimated from VNIR reflectance image. Various surface emissivity retrieval algorithms based on NDVI and vegetation proportion were applied to ascertain emissivities of the various land cover categories in the study area in the spectral range of 10.4–12.5 μm. A minimum emissivity value of about 0.95 was observed over the reflective rock body with a maximum of about 0.99 over dense forest. A strong correlation was established between Landsat ETM+ reflectance band 3 and emissivity. Single channel based algorithms were adopted for surface radiance and brightness temperature. Finally, emissivity correction was applied on ‘brightness temperature’ to obtain LST. Estimated LST values obtained from various algorithms were compared with field ground measurements for different land cover categories. LST values obtained after using Valor’s emissivity and single channel equations were best correlated with ground truth temperature. Minimum LST is observed over dense forest as about 26 °C and maximum LST is observed over rock body of about 38 °C. The estimated LST showed that rock bodies, bare soils and built-up areas exhibit higher surface temperatures, while water bodies, agricultural croplands and dense vegetations have lower surface temperatures during the daytime. The accuracy of the estimated LST was within ±2 °C. LST comparison of ASTER and MODIS with Landsat has a maximum difference of 2 °C. Strong correlation was found between LST and spectral radiance of band 6 of Landsat-7 ETM+. Result corroborates the fact that surface temperatures over land use/land cover types are greatly influenced by the amount of vegetation present.     

A gravity wave analysis near to the Andes Range from GPS radio occultation data and mesoscale numerical simulations: Two case studies

Global maps of potential wave energy per unit mass, recently performed with the Global Positioning System (GPS) Radio Occultation (RO) technique and different satellite missions (CHAMP and SAC-C since 2001, GRACE and COSMIC since 2006) revealed in Argentina, at the eastern side of the highest Andes Mountains, a considerable wave activity (WA) in comparison with other extra-tropical regions. The main gravity wave (GW) sources in this natural laboratory are deep convection (mainly during late Spring and Summer), topographic forcing and geostrophic adjustment.