A feasibility study for the detection of the diurnal variation of tropospheric NO2 over Tokyo from a geostationary orbit

We have conducted a feasibility study for the geostationary monitoring of the diurnal variation of tropospheric NO₂ over Tokyo. Using NO₂ fields from a chemical transport model, synthetic spectra were created by a radiative transfer model, SCIATRAN, for summer and winter cases. We then performed a Differential Optical Absorption Spectroscopy (DOAS) analysis to retrieve NO₂ slant column densities (SCDs), and after converting SCDs into vertical column densities (VCDs), we estimated the precision of the retrieved VCDs. The simulation showed that signal-to-noise ratio (SNR) ? 500 is needed to detect the diurnal variation and that SNR ? 1000 is needed to observe the local minimum occurring in the early afternoon (LT13–14) in summer. In winter, the detection of the diurnal variation during LT08–15 needs SNR ? 500, and SNR ? 1000 is needed if early morning (LT07) and early evening (LT16) are included. The currently discussed sensor specification for the Japanese geostationary satellite project, GMAP-Asia, which has a horizontal resolution of 10 km and a temporal resolution of 1hr, has demonstrated the performance of a precision of several percent, which is approximately corresponding to SNR = 1000–2000 during daytime and SNR ? 500 in the morning and evening. We also discuss possible biases caused by the temperature dependence of the absorption cross section utilized in the DOAS retrieval, and the effect of uncertainties of surface albedo and clouds on the estimation of precisions.     

Structure and thermal control of panel extension satellite (PETSAT)

Panel ExTension SATellite (PETSAT) [S. Nakasuka, Y. Nakamura, Panel extension satellite (PETSAT)—a novel satellite concept consisting of modular, functional and plug-in panels, in: 24th International Symposium on Space Technology and Science, invited talk, 2004-o-2, 2004 [1]] is a satellite which is made of several “functional panels”. Each panel has a special dedicated function and various combinations of different kinds of functional panels enable PETSAT to deal with various mission requirement. Development of PETSAT requires four interface requirements. These are mechanical interface, thermal interface, electrical interface and information interface. In this paper, mechanical interface and thermal interface of PETSAT are especially focused on and introduced. In the development of PETSAT issues about mechanical interface corresponds to panel structure and deployment mechanism. The structure of PETSAT is designed so as to have light weigh, enough space for devices and high stiffness. And deployment system has simple mechanism to avoid vacuum metalizing and improve reliability. On the other hand, approaches for thermal interface [K. Higashi, S. Nakasuka, Y. Sugawara, H. Sahara, K. Koyama, C. Kobayashi, T. Okada, Thermal control of panel extension satellite (PETSAT), in: 25th International Symposium on Space Technology and Science, 2006-j-02, 2006 [2]] are homogenization of temperature within panel and between panels. Homogenization of temperature within panels can be realized by heat lane plate, and that between panels is realized by magnetic fluid loop with magnetic heat pump. These approaches for mechanical and thermal interface are demonstrated in SOHLA-2 [Y. Sugawara, S. Nakasuka, T. Eishima, H. Sahara, Y. Nakamura, K. Koyama, C. Kobayashi, T. Okada, Elemental technologies for realization of panel extension satellite (PETSAT), in: 25th International Symposium on Space Technology and Science, 2006-J-01, 2006 [3]] that is satellite of technology demonstration for PETSAT.     

Sounding rocket experiment of bare electrodynamic tether system

An overview of a sounding rocket, S-520-25th, project on space tether technology experiment is presented. The project is prepared by an international research group consisting of Japanese, European, American, and Australian researchers. The sounding rocket will be assembled by the ISAS/JAXA and will be launched in the summer of 2009. The sounding rocket mission includes two engineering experiments and two scientific experiments. These experiments consist of the deployment of bare electrodynamic tape tether in space, a quick ignition test of hollow cathode system in space, the demonstration of bare electrodynamic tether system in space, and the test of the OML (orbital-motion-limit) current collection theory.     

Experiments and numerical simulations of an electrodynamic tether deployment from a spool-type reel using thrusters

The amount of space debris is ever increasing, and pollution of the space environment has become a serious problem that can no longer be ignored. Consequently, the active removal of large space debris from crowded economically useful orbits should begin as soon as possible. The Japan Aerospace Exploration Agency has been investigating an active debris removal system that employs highly efficient electrodynamic tether (EDT) technology for orbital transfer. This study investigates the tether deployment from a spool-type reel using thrusters by means of numerical simulations of an EDT system. The thrusters are used in order to ensure the deployment of a tether with the length of several kilometers. In the simulations using a multiple mass tether model, the key parameters are estimated from various on-ground experiments. By means of the numerical simulations, the dynamics of tether deployment is studied and requirements of thruster needed for the deployment, such as the thrust forces and the periods of thruster activation, are clarified.