Onboard sensor orientation analysis with kriging method

We propose in this paper a method to analyse the efficiency of the direction pointed by an infrared sensor dedicated to forest fire detection on board of a space vehicle. The objective is to use these sensors to detect forest fires on a defined territory with a specified probability. One way to verify that the system stands this specification is to test each possible configuration (pointing direction of the sensor and number of space vehicles) and estimate the corresponding probability of forest fire detection. However, when the coverage territory is wide or when the number of vehicles is important, it is hardly possible to simulate every configuration in a reasonable amount of time. We propose to use kriging method for the prediction of forest fire detection probability for all possible configurations.     

Multiple moving target detection and trajectory estimation using a single SAR sensor

A novel methodology is presented for determining the velocity and location of multiple moving targets using a single strip-map synthetic aperture radar (SAR) sensor. The so-called azimuth position uncertainty problem is therefore solved. The method exploits the structure of the amplitude and phase modulations of the returned echo from a moving target in the Fourier domain. A crucial step in the whole processing scheme is a matched filtering, depending on the moving target parameters, that simultaneously accounts for range migration and compresses two-dimensional signatures into one-dimensional ones without losing moving target information. A generalized likelihood ratio test approach is adopted to detect moving targets and derive their trajectory parameters. The effectiveness of the method is illustrated with synthetic and real data covering a wide range of targets velocities and signal-to-clutter ratios (SCRs). Even in the case of parallel to platform moving target motion, the most unfavorable scenario, the proposed method yields good results for, roughly, SCR > 10 dB.     

Microgravity effects on water supply and substrate properties in porous matrix root support systems.

The control of water content and water movement in granular substrate-based plant root systems in microgravity is a complex problem. Improper water and oxygen delivery to plant roots has delayed studies of the effects of microgravity on plant development and the use of plants in physical and mental life support systems. Our international effort (USA, Russia and Bulgaria) has upgraded the plant growth facilities on the Mir Orbital Station (OS) and used them to study the full life cycle of plants. The Bulgarian-Russian-developed Svet Space Greenhouse (SG) system was upgraded on the Mir OS in 1996. The US developed Gas Exchange Measurement System (GEMS) greatly extends the range of environmental parameters monitored. The Svet-GEMS complex was used to grow a fully developed wheat crop during 1996. The growth rate and development of these plants compared well with earth grown plants indicating that the root zone water and oxygen stresses that have limited plant development in previous long-duration experiments have been overcome. However, management of the root environment during this experiment involved several significant changes in control settings as the relationship between the water delivery system, water status sensors, and the substrate changed during the growth cycles.     

Light scattering in planetary atmospheres

This paper reviews scattering theory required for analysis of light reflected by planetary atmospheres. Section 1 defines the radiative quantities which are observed. Section 2 demonstrates the dependence of single-scattered radiation on the physical properties of the scatterers. Section 3 describes several methods to compute the effects of multiple scattering on the reflected light.     

Growth of wheat under one tenth of the atmospheric pressure.

Wheat plants were grown in twin closed growth chambers under normal and reduced atmospheric pressures. For the first 22 days from sowing, the reduced pressure was maintained at 200 hPa, and at 100 hPa for the remaining 27 days until harvest. These pressures were obtained by evacuation of the chamber and adding oxygen (170 and 79 hPa respectively) and carbon dioxide (0.65 and 1.0 hPa respectively; about 2 and 3 times above the control). Eighty-seven per cent of the final dry mass was produce under 100 hPa treatment. Growth and development of wheat are not negatively affected by low pressure treatment. Compared to the control, final dry mass increased by 76%, leaf number by 133%, and ear number by 35%, probably due to elevation of CO2. Shortening of shoot parts and increases in chlorophyll and proteins content are not in accordance with a predicted CO2 effect and could be attributed to the N2 removal and the subsequent alteration in gas diffusion rate.     

Three-dimensional numerical studies of a jet airflow around the duct platforms of the turbine nozzle clusters

This paper presents the results of three-dimensional numerical studies of hydrodynamics and heat exchange on the models of flat plates in the jet airflow. These results are compared with the experimental data. A three-dimensional model for determining the thermal condition of the nozzle clusters in the conjugated formulation is proposed. Also presented are the data on optimization of the system used for the jet airflow around the duct platforms of the nozzle clusters.     

Fiber-optic gyros and quartz accelerometers for motion control

In article the opportunity of use strapdown inertial navigation system (SINS) on the base of fiber-optic gyroscopes and quartz accelerometers corrected from star sensors and satellite navigation equipment (SNE) for perspective interplanetary spacecrafts motion control on phases of interplanetary trajectory insertion, trajectory correction, and braking during transition to Mars orbit is investigated. Results of onboard control complex accuracy characteristics estimation are presented at the given dynamic spacecraft scheme which is taking into account the liquid oscillations in tanks and structure elements elasticity. At modelling the errors of measuring devices installation, errors of SINS initial alignment and instrumental errors of SINS sensitive elements, variation of control engines parameters were taken into account. The structure of the developed complex of imitation modelling of interplanetary spacecraft controlled motion is resulted. Estimations of active flight legs realization accuracy were received by a method of statistical modelling of spacecraft controlled motion     

Radiation measurements on the flight of IML-2.

The second flight of the International Microgravity Laboratory (IML-2) on Space Shuttle flight STS-65 provided a unique opportunity for the intercomparison of a wide variety of radiation measurement techniques. Although this was not a coordinated or planned campaign, by sheer chance, a number of space radiation experiments from several countries were flown on this mission. There were active radiation measuring instruments from Japan and US, and passive detectors from US, Russia, Japan, and Germany. These detectors were distributed throughout the Space Shuttle volume: payload bay, middeck, flight deck, and Spacelab. STS-65 was launched on July 8, 1994, in a 28.45 degrees x 306 km orbit for a duration of 14 d 17 hr and 55 min. The crew doses varied from 0.935 mGy to 1.235 mGy. A factor of two variation was observed between various passive detectors mounted inside the habitable Shuttle volume. There is reasonable agreement between the galactic cosmic ray dose, dose equivalent and LET spectra measured by the tissue equivalent proportional counter flown in the payload bay with model calculations. There are significant differences in the measurements of LET spectra measured by different groups. The neutron spectrum in the 1-20 MeV region was measured. Using fluence-dose conversion factors, the neutron dose and dose equivalent rates were 11 +/- 2.7 microGy/day and 95 +/- 23.5 microSv/day respectively. The average east-west asymmetry of trapped proton (>3OMeV) and (>60 MeV) dose rate was 3.3 and 1.9 respectively.     

Progress in ultrasonic bioreactors for CELSS applications.

An important issue in Controlled Ecological Life Support Systems (CELSS) is the recycling of inedible crop residues to recover inorganic plant nutrients such as nitrates, phosphates, potassium and other macro- and micro-nutrients. In a closed system in space, such regeneration is vital to the long term viability of plant growth necessary for the food production and waste handling process. Chemical approaches to recycling such as incineration and wet oxidation are not compatible with low energy and environmentally friendly regeneration of such nutrients. Biological regeneration is more acceptable environmentally, but it is a very slow process and does not typically result in complete recovery of inorganic and organic nutrients. A new approach to biological regeneration is described here involving the combined use of special enzymatic catalysts and ultrasonic energy in a bioreactor system. This new system has the potential for rapid, efficient, environmentally friendly and complete conversion of crop wastes to inorganic plant nutrients and food recovery from cellulose materials. A series of experimental tests were carried out with a soybean crop residue meal substrate. Biochemical conversion rates were significantly expedited with the addition of enzymes and further enhanced through ultrasonic stimulation of these enzymes. The difference in conversion rates was particularly increased after the initial period of soluble organics conversion. The remaining cellulose substrate is much more difficult to biodegrade, and the ultrasonically-enhanced reaction was able to demonstrate a much higher rate of substrate conversion.     

Gravitaxis and graviperception in Euglena gracilis.

Gravitactic orientation in the flagellate Euglena gracilis is mediated by an active physiological receptor rather than a passive alignment of the cells. During a recent space flight on the American shuttle Columbia the cells were subjected to different accelerations between 0 and 1.5 x g and tracked by computerized real-time image analysis. The dependence of orientation on acceleration followed a sigmoidal curve with a threshold at < or = 0.16 x g and a saturation at about 0.32 x g. No adaptation of the cells to the conditions of weightlessness was observed over the duration of the space mission (12 days). Under terrestrial conditions graviorientation was eliminated when the cells were suspended in a medium the density of which (Ficoll) equaled that of the cell body (1.04 g/ml) and was reversed at higher densities indicating that the whole cytoplasm exerts a pressure on the respective lower membrane. There it probably activates stretch-sensitive calcium specific ion channels since gravitaxis can be affected by gadolinium which is a specific inhibitor of calcium transport in these structures. The sensory transduction chain could involve modulation of the membrane potential since ion channel blockers, ionophores and ATPase inhibitors impair graviperception.