The Design And Implementation Of Spaceborne Plasma Sounding System

Plasma is distributed in the vast space environment.In recent decades,with the development of aircraft and satellite technology,plasma detection technology tends to mature.The plasma in the earth’s space environment mainly originates from the solar wind composed of high-energy particles accelerated by the solar corona.Due to the obstruction of the geomagnetic field,the plasma flow in the solar wind forms a complex layered space environment around the earth.Through the plasma detection,the temporal and spatial distribution,and dynamic characteristics of the plasma can be obtained.At the same time,it can be used for space weather forecast to ensure the safety of the satellite.In this paper,a spaceborne plasma sounding system is designed,which can detect the magnetosphere and top ionosphere by remote sensing,and also has passive detection function to receive very low frequency signals in the universe.The main work of this paper are as follows:1.The design scheme of the plasma sounding system is proposed.The system can perform plasma detection while taking into account ionospheric top measurement,and has active detection mode and passive detection mode.In the active detection mode,an orthogonal dipole antenna is adopted to transmit two-phase coded pulse.The receiving system contains three analog channels,and the plasma spatial-temporal distribution structure and dynamic characteristics are reversed according to the received echo signals.In passive detection mode,it can receive very low frequency signals in the universe,detect the thermal noise spectrum,and obtain local electron density information.2.The hardware and software design of the plasma sounding system is realized.The hardware platform is mainly composed of an antenna system,a transmitting system,a receiving system,and spaceborne data bus interfaces.The antenna system uses a dipole triad antenna,the pulse signal generated by the transmitting system is fed into the antenna system through the signal conditioning circuit and radiated into the space environment.When the signal frequency equals the plasma frequency,reflection occurs and the echo signal enters the receiving system by the antenna.After that,it is mixed and filtered by the receiving front end,and then input to the digital receiver after AD sampling.The digital receiver performs preliminary processing on the data,uses digital down conversion technology to reduce the data rate,and uses hardware pulse compression to improve the echo distance resolution.There are three kinds of data bus interface,including Ethernet interface,RS485 interface and LVDS interface.The software platform is based on embedded software design,which realizes device control,data storage and data transmission functions.3.The functional test and experimental verification of the plasma sounding system were carried out.The functional test part mainly measures the system’s sensitivity,gain,dynamic range,and intermediate frequency bandwidth.The experimental verification part includes ionospheric detection experiments and passive VLF experiments.The active detection capabilities of the system are verified by ionospheric detection experiments,and the passive detection capabilities of the system are verified by passive VLF experiments.The results show that the detection system meets the requirements of plasma detection.