Mechanism for assembling antenna in space

The development of large and precise space antennas is one of the most important topics in constructing space infrastructures. We evaluated an approach to assembling large and accurate space antennas which uses space robots. The assembly mechanism was launched together with the ETS-VII, the first telerobotic satellite from Japan, and its performance, including fully automatic assembling, was verified. The assembling-type antenna and the results of antenna assembly experiments are discussed     

Selection of sensors and spectral bands of marine observation satellite (MOS) — 1

After trading off the proposed requirements by the Committee on Earth Observation Satellite Development, cost and time for development of sensors, spacecraft and launch vehicle, the following sensors were selected for Marine Observation Satellite (MOS) - 1.(1) Four channel visible and near IR sensor (MESSR) with 50 meter resolution. (2) Four channel visible and thermal IR sensor (VTIR) with 0.9 km (visible) and 2.7 km (IR) resolution respectively. Out of three IR channels, two channels are atmospheric window channels while the third channel is water vapor absorption band. (3) Two channel microwave scanning radiometer (MSR) with responsivity in 23.8 and 31.4 GHz respectively. (4) Data collection system.     

Experiment for mapping land cover and it’s change in southeastern Sri Lanka utilizing 250 m resolution MODIS imageries

Utilizing freely available MODIS NDVI and Natural color imageries of 250 m spatial resolution produced by NASA, an experiment was made to map land-cover and its change with an emphasis on vegetation cover in southeastern Sri Lanka, which plays a vital role for control of green house gas. For the change detection purpose, 1987 land cover map made by present authors from Landsat MSS image and extensive ground truth survey data was used as the base map. The result of the experiment shows that MODIS data are useful to make a land cover map of 250 m spatial resolution for tropical areas with high cloud coverage like Sri Lanka. It was found that the forest cover decrease amounted as large as 21% in 19 years time span in southeastern Sri Lanka, the prominent forest region of the country. On the other hand homestead/vegetation and mixed vegetation/scrub dominant categories increased by 13.7% and 7.1%, respectively. These changes are considered due to a large clearance of forest areas for agriculture and building houses to accommodate increasing inhabitants.     

Environmental pattern change as revealed by Landsat MSS data

The environmental pattern change of land and sea surface are studied based on the MSS data of Landsat-1 and 2. The analysis of land use in Nagoya and Toyohashi areas located in central Japan indicates a large change of land use took place during 3 yr between 1972 and 1975. Land use change is especially large in the periphery and suburbs of large city Nagoya, the fourth largest city of Japan with 2 million population.Out of total studied area of 350 km² in Nagoya District, 5.79 and 3.20% were transformed into new urban and open areas respectively from forest, agricultural and suburban areas.Over the sea surface, “red tide” named after its color which causes damage to fishing industry is increasing in a bay and Seto Inland Sea. During the analysis a small vortex of approximately 40 km in diameter was found off the tip of Kii Peninsula in the periphery of Kuroshio, a large warm ocean current.It is the first time that the existence of this kind of small vortex is visually recognized near Japan along the Kuroshio. It is found that this vortex is manifested by the red tide driven into the vortex.     

Verification studies of MOS-1 sensors

The verification experiments with a breadboard model of MSR (Microwave Scanning Radiometer) to be installed in MOS-1 indicate a good possibility of observing snow properties, water surface and atmospheric water content. A verification program plan of MOS-1 sensors has been made by the committee consisting of 32 experts from 27 national institutes, laboratories, semigovernmental organzations and universities.To perform the verfication program plan, observations with the engineering models of the sensors from an airplane are scheduled in November and December of 1984 and the summer in 1985 and investigators from national research institutes and universities participate in the analsyses of the acquired data.     

Improvements in and actual performance of the Plant Experiment Unit onboard Kibo,the Japanese experiment module on the international space station

In 2004, Japan Aerospace Exploration Agency developed the engineered model of the Plant Experiment Unit and the Cell Biology Experiment Facility. The Plant Experiment Unit was designed to be installed in the Cell Biology Experiment Facility and to support the seed-to-seed life cycle experiment of Arabidopsis plants in space in the project named Space Seed. Ground-based experiments to test the Plant Experiment Unit showed that the unit needed further improvement of a system to control the water content of a seedbed using an infrared moisture analyzer and that it was difficult to keep the relative humidity inside the Plant Experiment Unit between 70 and 80% because the Cell Biology Experiment Facility had neither a ventilation system nor a dehumidifying system. Therefore, excess moisture inside the Cell Biology Experiment Facility was removed with desiccant bags containing calcium chloride. Eight flight models of the Plant Experiment Unit in which dry Arabidopsis seeds were fixed to the seedbed with gum arabic were launched to the International Space Station in the space shuttle STS-128 (17A) on August 28, 2009. Plant Experiment Unit were installed in the Cell Biology Experiment Facility with desiccant boxes, and then the Space Seed experiment was started in the Japanese Experiment Module, named Kibo, which was part of the International Space Station, on September 10, 2009 by watering the seedbed and terminated 2 months later on November 11, 2009. On April 19, 2010, the Arabidopsis plants harvested in Kibo were retrieved and brought back to Earth by the space shuttle mission STS-131 (19A). The present paper describes the Space Seed experiment with particular reference to the development of the Plant Experiment Unit and its actual performance in Kibo onboard the International Space Station. Downlinked images from Kibo showed that the seeds had started germinating 3 days after the initial watering. The plants continued growing, producing rosette leaves, inflorescence stems, flowers, and fruits in the Plant Experiment Unit. In addition, the senescence of rosette leaves was found to be delayed in microgravity.     

Optimization of Coverage Pattern for Regional Communications Satellite

An optimization problem of an antenna coverage pattern for a regional communications satellite when an antenna-pointing error exists is discussed. A new performance measure is introduced to evaluate the coverage pattern. This measure is defined as the statistical mean of the ratio between two areas, the full service area and the part of it covered by the antenna. The optimum coverage pattern which maximizes this measure under certain constraint is obtained. The results of numerical calculations are included to demonstrate the technique.     

A new type of magnetic gimballed momentum wheel and its application to attitude control in space

A new type of magnetically suspended gimbal momentum wheel utilizing permanent magnets is described. The bearing was composed of four independent thrust actuators which control the rotor thrust position and gimbal angles cooperatively, so that the bearing comes to have a simple mechanism with high reliability and light weight. The high speed instability problem due to the internal damping was easily overcome by introducing anisotropic radial stiffness. A momentum flywheel with the 3-axis controlled magnetic bearing displays good performance for attitude control of satellite with biased momentum.     

Formation of bioorganic compounds in planetary atmospheres by cosmic radiation.

Simulated planetary atmospheres (mixtures of simple gases) were irradiated with high energy particles to simulate an action of cosmic rays. When a mixture of carbon monoxide, nitrogen and water was irradiated with 2.8-40 MeV protons, a wide variety of bioorganic compounds including amino acids, imidazole, and uracil were identified in the products. The amount of amino acids was proportional to the energy deposit to the system. Various kinds of simulated planetary atmospheres, such as "Titan type" and "Jovian type", were also irradiated with high energy protons, and gave amino acids in the hydrolyzed products. Since cosmic rays are a universal energy source in space, it was suggested that formation of bioorganic compounds in planetary atmospheres is inevitable in the course of cosmic evolution.     

Advanced reaction wheel controller for attitude control of spacecraft

A design procedure is presented for an attitude control system consisting of a momentum wheel and a reaction wheel. Control laws are designed for this system using modern control techniques. The observer based method produces a control scheme which achieves a good transient response.