Satellite Key Technologies Of Electric Field Instrument

Space electric field is an important parameter to study space weather and space environment. The magnitude and change of its numerical value is related to solar activity, thunderstorm, earthquake, atmosphere environment pollution and so on. The foundation of the satellite-borne electric field instrument detecting system will remarkably improve the ability of the detection of weather, earthquake, space weather and space environment. It also provides new theory and technology for the development of space detection.This paper mainly studies the key technology of satellite-borne double probe electric field instrument.Because of the particularity of the electric field detection using the satellite-borne electric field instrument in space plasma, many outside factors will influence the detection precision. To avoid the influence of the outside factors, this paper analyses the influence factors at home and abroad which could disturb the detection in detail , emphatically introduces plasma gradient, satellite and probe support system, wake, plasma noise and the influence of outside magnetic field and satellite attitude on detection, and also present the method to avoid or weaken the influential factors.The probe for detection is designed and the shape, material, external coating and the detailed configuration parameters of the probe is introduced.The current source is introduced. The current source can provide aconstant current varying from -1. 28μA to 1. 28μA in 256 steps, which ischanged along with the input control voltage. Each step varied 10nA. The experimental measurement shows the max relative error of positive current source is 0. 9% and the max relative error of negative current source is 1.9%.Because the probe potential is unknown and is difficult to measure, it is difficult to obtain the bias current through the actual probe potential and find the optimum operating point of the probe .This paper presents a method to find the optimum operating point and validates it through experiment of simulating the probe photocurrent changes and the work situations of the probe in the plasma. The experiment shows that this method can obtain the probe potential which is mostly close to the potential of the ambient plasma and achieves the probe automatic adjusting.Based on the analysis of detection theory of satellite-borne electric field instrument, the design of a wide-band low noise preamplifier circuit used in the electric field instrument is introduced. Then the noise analysis of the preamplifier circuit and the method of reducing noise are presented. The bandwidth of this preamplifier circuit is 0～5MHz and theinput noise of the 100Hz~30KHz frequency range is only 0. 69μV.Finally, according to the need of the project, the detailed design of the whole satellite-borne double probe electric field instrument is presented.