Remote sensing of Earth resources: emerging opportunities for developing countries

Land information from remote sensing satellites contributes substantially to the quality of decision making in development activities. However, participation in space-related activities by developing countries has historically been low in part due to the high costs and advanced technology inputs required. The paper discusses several technological and socio-political trends which now offer increasingly affordable opportunities for developing countries to increase their level of participation in activities related to satellite remote sensing of earth resources. Benefiting from these opportunities requires appropriate encouragement and support from national governments.     

The FedSat Microsatellite Mission

An Australian research microsatellite, FedSat with a complement of four payloads was launched from Tanegashima, Japan on 14 December 2002 into a near-circular sun synchronous 10:30 LT polar orbit at an inclination of 98.7° and altitude 800 km. Scientific experiments include a triaxial fluxgate magnetometer with a frequency response up to 100 Hz and a GPS receiver to monitor total electron content (TEC) and provide a precise orbit determination. Communications experiments include a Ka-band transponder and a UHF packet data service. A high performance computer payload will test reconfigurable computing technology. This revised version was published online in August 2006 with corrections to the Cover Date.     

Intracellular molecular distributions in spacecraft experiments in orbit around Earth

It is possible that the nucleolous inside the cell plays the role of a “gravity receptor”. Furthermore, cells up to 10 μm in diameter can demonstrate some effect due to the redistribution of mitochondria or nucleolous. Effects of gravity should be present in various cell systems where larger objects such as the ribosomes move from cell to cell. In this paper we study the effects of gravity on cells. In particular, we examine the resulting intracellular molecular distribution due to Brownian motion and the ordered distribution of molecules under the action of gravity, where n₀ is the number per unit volume at certain level, and n is the number per unit volume above that level. This is an experiment that takes place at a certain orbital altitude in a spacecraft in orbit around Earth, where the acceleration due to the central field is corrected for the oblateness and also the rotation of the Earth. We found that equatorial circular and elliptical orbits have the highest n/n₀ ratios. This experiment takes place in circular and elliptical orbits, with eccentricities e = 0, 0.1 and involves a bacterial cell at an orbital altitude of 300 km. We found that n/n₀ = 1.00299 and 1.0037 respectively, which is still a 0.6–0.7 % higher than n/n₀ = 0.0996685 calculated on the surface of the Earth. Examining mitochondria in similar orbital experiments we found that equatorial orbits result to higher n/n₀ ratios. In particular, we found that n/n₀ = 8.38119, where an elliptical orbit of eccentricity e = 0.1 results to n/n₀ = 13.8525. Both are high above 100%, signifying the importance of Brownian motion over gravity. Our results are of interest to biomedical applications. Molecular concentrations are important for various processes such as the embryogenesis, positional homeostasis and its relation to cell energy expenditure, cell torque, cell deformation, and more. These results indicate that statistical molecular distributions play an important role for the recognition of a particular environment by the cell, in biological space experiment to come.     

Regolith effects in planetary X-ray fluorescence spectroscopy: Laboratory studies at 1.7–6.4 keV

Laboratory measurements are presented to study the effects of the physical properties of regolith on planetary soft X-ray fluorescence spectroscopy. Two laboratory setups are used to independently measure these regolith effects using lunar regolith analog samples with three different particle-size ranges. Discussion is given on the data analysis. Some of the data may be valid only for qualitative conclusions. Analytical modelling is used to separate the effects expected for a plane-parallel and homogeneous medium from those of measured regolith analogs. The surface roughness and porosity of the regolith are observed to induce an enhancement of the higher-energy part of the spectrum as a function of the incidence angle. The enhancement is larger for rougher surfaces. A brief discussion is given on the relevance of this study for future planetary missions carrying soft X-ray spectrometers.     

FM Telemetry for Multiple Force Measurements on Free-Flying Models

The extension of the FM telemetry technique to provide simultaneous measurements of four forces acting on a free-flight aerodynamic model is reported. Developments and procedures required to achieve the accuracy, linearity, and stability necessary for obtaining dynamic stability coefficients are described. System accuracy is believed to be better than 3 percent. Free-flight data, presented in the form of aerodynamic stability derivatives, are in good agreement with measurements taken by conventional methods under the same aerodynamic conditions.     

Altimetry,bathymetry and geoid variations at the Gavdos permanent Cal/Val facility

The aim of this work has been to examine the relationship of steep bathymetry in the coastal areas around the permanent Cal/Val facility of Gavdos, and their influence on the produced calibration values for the Jason-2 satellite altimeter. The paper describes how changes in seafloor topography (from 200 to 3500 m depth over a distance of 10 km) are reflected on the determined altimeter parameters using different reference surfaces for satellite calibration. Finally, it describes the relation between these parameter trends and the region’s local characteristics.     

The USA and the 1985 space WARC

This article considers the US policy objectives at the forthcoming WARC-ORB 85 Conference, and argues that with US willingness to modify its position the Conference seems for the first time to provide a good basis for a dialogue between the USA and those countries that feel the existing system is not equitable. Two main problems still need to be considered: the role of common user organizations such as INTELSAT, and the relationship between the Federal Communications Commission and other actors involved in the US international telecommunication decision-making process. Failure to reach agreement at the conference could lead to the USA being the country which suffers most.     

Early renal changes in 45 degrees HDT rats

Background: Both microgravity and simulated microgravity models, such as the 45HDT (45 degrees head-down tilt), cause a redistribution of body fluids indicating a possible adaptive process to the microgravity stressor. Understanding the physiological processes that occur in microgravity is a first step to developing countermeasures to stop its harmful effects, i.e., (edema, motion sickness) during long-term space flights. Hypothesis: Because of the kidneys' functional role in the regulation of fluid volume in the body, it plays a key role in the body's adaptation to microgravity. Methods: Rats were injected intramuscularly with a radioactive tracer and then lightly anesthetized in order to facilitate their placement in the 45HDT position. They were then placed in the 45HDT position using a specially designed ramp (45HDT group) or prone position (control group) for an experimental time period of 1 h. During this period, the 99mTc-DTPA (technetium-labeled diethylenepentaacetate, MW=492 amu, physical half-life of 6.02 h) radioactive tracer clearance rate was determined by measuring gamma counts per minute. The kidneys were then fixed and sectioned for electron microscopy. A point counting method was used to quantitate intracellular spaces of the kidney proximal tubules. Results: 45HDT animals show a significantly (p=0.0001) increased area in the interstitial space of the proximal tubules. Conclusions: There are significant changes in the kidneys during a 1 h exposure to a simulated microgravity environment that consist primarily of anatomical alterations in the kidney proximal tubules. The kidneys also appear to respond differently to the initial periods of head-down tilt.     

Satellite remotely-sensed land surface parameters and their climatic effects for three metropolitan regions

By using both high-resolution orthoimagery and medium-resolution Landsat satellite imagery with other geospatial information, several land surface parameters including impervious surfaces and land surface temperatures for three geographically distinct urban areas in the United States – Seattle, Washington, Tampa Bay, Florida, and Las Vegas, Nevada, are obtained. Percent impervious surface is used to quantitatively define the spatial extent and development density of urban land use. Land surface temperatures were retrieved by using a single band algorithm that processes both thermal infrared satellite data and total atmospheric water vapor content. Land surface temperatures were analyzed for different land use and land cover categories in the three regions. The heterogeneity of urban land surface and associated spatial extents were shown to influence surface thermal conditions because of the removal of vegetative cover, the introduction of non-transpiring surfaces, and the reduction in evaporation over urban impervious surfaces. Fifty years of in situ climate data were integrated to assess regional climatic conditions. The spatial structure of surface heating influenced by landscape characteristics has a profound influence on regional climate conditions, especially through urban heat island effects.