STUDY OF PLANETARY MAGNETOSPHERES BY DEVELOPING SPACE-VEHICLE-BORNE FAST CORRELATION-SPECTROMETER
Grant-in-Aid for General Scientific Research (C)
|Allocation Type||Single-year Grants|
|Research Institution||TOYAMA PREFECTURAL UNIVERSITY|
OKADA Toshimi TOYAMA PREFECTURAL UNIVERSITY, ASSOCIATE PROFESSOR, 工学部, 助教授 (90008566)
|Project Period (FY)
1991 – 1992
Completed(Fiscal Year 1992)
|Budget Amount *help
¥1,000,000 (Direct Cost : ¥1,000,000)
Fiscal Year 1992 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1991 : ¥500,000 (Direct Cost : ¥500,000)
|Keywords||SPECTRUM ANALYSIS / CORRELATION METHOD / MARS SPACECRAFT / VLF / MAGNETOSPHERE / DATA COMPRESSION / 火星探査機 / VLF / DC電場 / 電波 / 衛星観測 / スペクトル / フ-リエ変換法|
Direct measurements of plasma wave activities concerned with the energy transfer are essentially important in order to study the interaction between the planetary magnetosphere and the solar wind. Waves in wide frequencies and large-scale electric fields should be observed in the future exploration program of the planetary upper atmosphere. In this present project we have developed an apparatus to measure the spectra of the waves generated in the planetary magnetosphere such as Mars and Jupiter as well as in the interplanetary space. The apparatus is designed to have specification matched with the payload conditions of the spacecraft. We have made cleared the following points :
(1) From data analysis of the earth s magnetosphere observed by the EXOS-D satellite and works on the planetary magnetospheres, the waves are found to be simultaneously generated in the range from DC to high frequency in many cases. This fact leads us to separate the extremely low-frequency components from high-f
requency components in the spectral analysis. The extremely low-frequency components are sampled in multi-bits and the data can be easily telemetered while the high-frequency components are analysed by the low-bit correlation method.
(2) Spectra of the stationary and quasi-stationary signals are well measured by the one-bit correction method ; hiss-type signals and whistling atmospherics are confirmed to be well identified.
(3) Wave polarization is estimated by the cross-correlation method when one of the signal is multi-bit sampled and correlated with the other signal sampled by one-bit. Therefore the data to be stored or telemetered is much reduced.
(4) The absolute power of the short-duration signal such as an impulse cannot always be accurately measured by the one-bit correlation This may be an weak point of the low-bit correlation method.
(5) By means of the data compression techniques such as CODEC and Differential PCM, the number of data telemetered is reduced by more than 30 %.
(6) The sensor of electric field for wide-band observation including DC component is established.
From these results, we conclude that the low-bit correlation method is an option to the conventional spectral and polarization analysis technique matched with the small payload condition of the spacecraft. Less
Research Output (13results)