STUDY OF PLANETARY MAGNETOSPHERES BY DEVELOPING SPACE-VEHICLE-BORNE FAST CORRELATION-SPECTROMETER

直接测量与能量传递有关的等离子体波活动对于研究行星磁层与太阳风之间的相互作用至关重要。在未来的行星高层大气探测计划中，应该观测到宽频率波和大尺度电场。在本项目中，我们已经开发了一种装置来测量在行星磁层（如火星和木星）以及行星际空间中产生的波谱。该装置的设计规格与航天器的有效载荷条件相匹配。（1）通过对EXOS-D卫星观测的地球磁层数据和行星磁层工作的分析，发现在许多情况下，从直流到高频的波是同时产生的。这一事实使我们能够将极低频分量与高频分量分开， 关于我们 在光谱分析中，对极低频分量采用多比特采样，便于遥测;对高频分量采用低比特相关法进行分析。(2)用一位校正法较好地测量了平稳和准平稳信号的频谱，证实了对嘶嘶型信号和哨声大气的识别。(3)当其中一个信号是多比特采样的，并且与另一个信号是一比特采样的时，利用互相关方法估计波的极化。因此，要存储或遥测的数据大大减少。(4)对于脉冲等短脉冲信号，用一位相关法不能准确地测量其绝对功率，这可能是低位相关法的一个弱点。(5)采用CODEC和差分PCM等数据压缩技术，使遥测数据量减少30%以上。(6)建立了包含直流分量的宽频带电场观测传感器，并对低比特相关法进行了研究，结果表明，低比特相关法是适合航天器小载荷条件下常规谱极化分析技术的一种选择。少

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 … More 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