On-Orbit Operation Results of the World\u27s First CubeSat XI-IV – Lessons Learned from Its Successful 15-years Space Flight

In recent years, the size and cost of satellites have been reduced, and the frequent launch of satellites have been realized even by small private companies and universities. The first step of this big wave was the first successful launch of CubeSats, 1kg nano-satellites, in June 2003. One of the CubeSats was XI-IV, which was developed by Intelligent Space Systems Laboratory (ISSL) of the University of Tokyo. Its mission was the world’s first on-orbit demonstration of the CubeSat bus system. Due to the spatial, power and cost constraints, most of the bus system was composed of low-cost COTS parts, and a “cross-check” type fault redundancy system against the radiation effects was implemented to achieve as better reliability as possible within the resource constraints. Since the successful launch by the ROCKOT launch vehicle from Russia, the satellite has been in normal operation for over fifteen years since the launch (as of June 2019). The operation has been jointly conducted by the University of Tokyo and amateur radio operators in Japan. This paper reports its more-than-15-years world\u27s longest CubeSat operation results and the lessons learned from it

Assembly of a new gas-diffusion unit and its application to the determination of total carbonate and ammoniacal nitrogen by FIA.

今回新たに多孔質PTFE(polytetrafluoroethylene)チューブを分離膜とするガス透過装置を試作し,その性能について総炭酸定量用FIA装置を用いて検討した.新しいガス透過装置は組み立てが簡単で,前回製作のものに比べ,約10%の感度向上が達成され,更にピークのテイリングも減少した.本装置を組み込んだFIAにより環境水中の総炭酸,アンモニア態窒素の定量が可能である.いずれの場合もpH変化に伴うクレゾールレッドの呈色変化を測定に利用した.本法によれば多孔質ガス透過チューブ長8cmのとき,172mg dm(-3)(4×10(-3)mol dm(-3))以下の総炭酸を1時間当たり20試料,3.6mg dm(-3)(2.6×10(-4)mol dm(-3))以下のアンモニア態窒素を1時間当たり30試料の速さで測定できた.この際の検出限界(S/N=3に相当)は総炭酸の場合,0.96mg dm(-3)(2×10(-5)mol dm(-3)),アンモニア態窒素の場合は30μg dm(-3)(2×10(-6)mol dm(-3))であった.A new gas-diffusion unit was constructed and applied to determine total carbonate or ammoniacal nitrogen in water by spectrophotometric FIA. The gas diffusion unit, which was constructed without any glue, could be assembled easily by fastening the screws to tee connectors with ferrules. The new gas-diffusion unit was improved to decrease the dead volume. The unit gave sharper peaks than the previous one, and peaks higher by 10% in the case of CO(2) determination. The gas-diffusion part consisted of an inner microporous polytetrafluoroethylene (PTFE) tube (GORE-TEX®, 1.0 mm i.d., 1.8 mm o.d., pore size 2.0 μm, porosity 50%) and an outer PTFE tube (2.0 mm i.d., 3.0 mm o.d.). Sample solution was injected into the carrier solution (CS), in which the analyte was converted to a gaseous substance which passed through the microporous PTFE membrane to be mixed with the reagent solution (RS) flowing in the space between the outer and the inner tubings. The resulting pH shift caused the color of the indicator in RS to change. The conditions for the determination of total carbonate are as folows; CS was 1.8X×10(-3) mol dm(-3) H(2)SO(4), RS contained Cresol Red (at pH 9.0) and the detection wavelength was 410 nm. The detection limit was 0.96 mg dm(-3) CO(2) (S/N=3), the response was linear up to 172 mg dm(-3), and the sampling rate was 20 h(-1). For ammoniacal nitrogen, CS was 10(-2) mol dm(-3) NaOH, RS contained Cresol Red (pH 7.0) and absorbance was measured at 550 nm. The detection limit was 30μg dm(-3)NH(4)(+)-N (S/N=3), the response was linear up to 3.5 mg dm(-3), and the sampling rate was 30 h(-1). Total carbonate and ammoniacal nitrogen in river and seawater samples were determined satisfactorily

Development of Rapid Sampling System of Atmospheric Water Vapor for Tritium Measurement

We have developed a rapid sampling system for measuring the tritium in atmospheric water vapor. The system consists of a high-efficiency particulate air filter cartridge, an oil-free compressor, a water-vapor-separating module with hollow fiber membranes, two cold traps, and an oil-free rotary pump. Compressed air (0.4 - 0.7MPa) is introduced into the water-vapor-separation module, which consists of a stainless steel column containing polyimide membrane tubes. Water vapor permeates through the tubes and is collected by cold traps cooled with dry ice and ethanol. The module is heated with a flexible heater to control its temperature. We have determined the recovery yields under various sampling conditions and find that this system can collect atmospheric water vapor with a recovery yield of >99%. This system can thus be a useful tool for understanding short-term observations of tritium in atmospheric water vapor

Japanese population dose from natural radiation

The radiation doses from natural radiation sources in Japan are reviewed using the latest knowledge. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and the Nuclear Safety Research Association report the annual effective doses from cosmic rays, terrestrial radiation, inhalation, and ingestion as natural sources. In this paper, the total annual effective dose from cosmic-ray exposure is evaluated as 0.29 mSv. The arithmetic mean of the annual effective dose from external exposure to terrestrial radiation is 0.33 mSv for the Japanese population using the data of nationwide surveys by the National Institute of Radiological Sciences. Previously in Japan, although three different groups have conducted nationwide indoor radon surveys using passive-type radon monitors, to date only the Japan Chemical Analysis Center (JCAC) has performed a nationwide radon survey using a unified method for radon measurements conducted indoor, outdoor, and in the workplace. Consequently, the JCAC results are used for the annual effective dose from radon and that for radon inhalation is estimated as 0.50 mSv using a current dose conversion factor. In this paper, UNSCEAR values are used for the mean indoor and outdoor thoron-progeny concentrations, and the annual effective dose from thoron is reported as 0.09 mSv. Thus, the annual effective dose from radon and thoron inhalation is 0.59 mSv. From a JCAC large-scale survey of foodstuffs, the committed effective dose from the main radionuclides in dietary intake is 0.99 mSv. Finally, the Japanese population dose from natural radiation is given as 2.2 mSv, which is similar to the reported global average of 2.4 mSv

Investigation of Snow Cover Effects and Attenuation Correction of Gamma Ray in Aerial Radiation Monitoring

In aerial radiation monitoring (ARM), the air dose rate cannot be appropriately estimated under snowy conditions due to attenuation of gamma rays by the snow layer. A technique to address this issue is required for ARM to obtain enough signals for air dose rates. To develop this technique, we investigated the relationship between snow depth and ARM measurement results using ARM, laser imaging detection and ranging, and ground measurement before and after snowfall. From the measured data, the results obtained using three different correction factors were examined and compared. An appropriate correction improved the underestimation of the air dose rate. However, further improvement in the accuracy of the analysis requires accurate estimation of the snow water equivalent