Navigation Based On X-ray Pulse Timing Circuit Of Detection System Research

The astronomical navigation has high navigation accuracy, and could be usedwithout restriction, etc. It is an important trend of spacecraft navigation in future. TheTOA (time of arrival) of X-ray pulse can provide accurate time standards to spacecraft,which not only enhances the autonomy of spacecraft navigation (because it don’t needto rely on the support of ground station), but also increases the long-term stability oftime standards because its long-term stability is similar to cesium atomic clock.Therefore, it is an important strategic significance to develop active navigation based onX-ray pulsar.Therefore, X-ray photon counting detector based on MCP is used to measure TOAof X-ray pulse in this paper. The front-end electronics is an important part of the groundsimulation system, which is used to discriminate and complete timing for the effectiveoutput signals of detector. Firstly, according to the requirements of the detector fornavigation based on X-ray pulsars, the X-ray photon counting detector based on MCP ischosen as detector for ground simulation system by comparing the advantages anddisadvantages of various X-ray detectors. And according to the characteristics of thedetector output signals and the advantages and disadvantages of various timingtechnology, we have designed two kinds of timing scheme: peak timing and constantfraction timing. Because there are two kinds of shaping schemes in constant fraction,two constant fraction timing systems are designed and named No.1constant fractiontiming system and No.2constant fraction timing system. The verification andcomponents selection of two kinds timing schemes are comprehensively discussed indetail in this paper. The timing functions of three timing system are successfullyimplemented by hardware circuit, and the debug waveforms of test results are acquired.Timing accuracy and dead time are important parameters of timing systems.Experimental program of timing accuracy measurement has been designed. And the experimental results show that the timing accuracy of peak timing system and constantfraction system are18ns and0.78ns. The dead time of detection system with differenttiming system has been acquired by analyzing the distribution of the adjacent detectedphoton events interval time. The dead time of the system with peak timing system is4.75μs, and the constant fraction system is105ns. Three timing systems are used inground simulation system. The pulse profiles are reconstructed by using the groundsimulation system with three timing systems. Comparing signal to noise ratio (SNR) ofpulse profiles with different value Bin, when the pulse period is300ms and dataquantity is6550, the Bin value is1.5ms to make the SNR to be the best. Comparing thecounting rate of detection system and SNR of the pulse profiles with different timingsystem, and the counting rate of detection system with No.2constant fraction timingsystem is the highest, and the SNR of the detection system with No.1constant fractiontiming system is the highest. The threshold value and supply voltage of No.2constantfraction timing system how to affect the counting rate and SNR are discussed in thispaper. When the threshold value is larger, the SNR is higher and the counting rate islower. And when the supply voltage is±5.2V, the experimental result is the optimal.