Research On Radial Velocity Measurement Technology Based On Doppler Asymmetric Space Heterodyne Interferometer

With the development of aerospace technology,more and more spacecrafts are being sent into deep space orbit.In order to reduce ground support costs and improve the spacecraft's ability to autonomously operate and survive on-orbit,it must be capable of autonomous navigation and self-control.The speed-measurement-based autonomous astronomical navigation method effectively avoids the influence of calculus on the speed parameter,making it have a broad application prospects in the field of autonomous navigation in deep space exploration.Compared with other passive radial velocity measurement instruments,the Doppler Asymmetri Spatial Heterodyne(DASH)interferometers do not require moving optical parts and can be built in rugged,compact packages,which are more suitable for autonomous astronomical navigation in deep space exploration.The radial motion between the deep space detector and the star causes the star's spectrum to be Doppler shifted,resulting in a phase shift of the interference fringes receieved by a DASH instrument.Then,the radial velocity can be solved by measuring this phase shift.In order to use the DASH instrument to measure the radial velocity with high precision,the influence of detector noise and ambient temperature on the accuracy of radial velocity measurement was studied,and the optimal optical path difference at the maximum phase shift sensitivity was given.In addition,the problem of solving the radial velocity from the absorption line is transformed into the radial velocity from the emission line through the theoretical derivation,which provides an effective technical approach for the application of DASH spectroscopy technology to radial velocity measurement from absorption linesThe main research contents of the paper are as follows:First of all,the principle of measuring radial velocity by DASH spectroscopy technology is introduced in detail,and the structure of DASH interferometer is given.After that,the effects of parameters such as sampling optical path difference and field of view on the performance of the DASH interferometer are analyzed.The research shows that the interference fringe phase shift is proportional to the sampling optical path difference,which means that the phase shift sensitivity can be improved by changing the optical path difference.In addition,the spectral characteristics of stars are analyzed,and it is pointed out that stellar spectral lines contain both emission lines and absorption lines.In order to deal with the complex and changeable environment of deep space navigation,DASH spectroscopy technology needs to be able to achieve highprecision radial velocity extraction under both spectral lines.Secondly,the optimal optical path difference calculation formula is given by analyzing the influence of the sampling optical path difference on the sensitivity of the interference fringe phase shift.Aiming at the problem that the spectral resolution of the DASH interferometer is not high enough to distinguish the multiple emission lines of the star,a data processing method that directly calculates the phase shift of the spectral wave packet is proposed,which not only ensures the accuracy of radial velocity inversion,but also reduces the requirements for the spectral resolution of the DASH interferometer.In addition,the effects of detector noise and ambient temperature on radial velocity measurement accuracy have been studied through theoretical analysis and laboratory experiments.The indoor experimental results are consistent with theoretical derivation,and it is shown that increasing the interference fringe contrast can effectively suppress the phase drift introduced by the detector noise,and the phase drift introduced by changes in ambient temperature can be tracked by simultaneously introducing reference light with similar frequencies.Finally,the light intensity distribution of interference fringes generated by the stellar absorption spectrum is theoretically deduced,and a radial velocity inversion method based on the absorption spectrum is proposed.The theoretical research results indicate that the interference fringes from absorption spectrum are the result of superimposing the interference fringes generated from the contour line without frequency shift and the interference fringes generated from the absorption line with frequency shift.According to their different coherence lengths,the interference fringes related to the absorption line can be separated by extracting part of the interference fringes,and then the radial velocity can be extracted using the interference fringe data processing method for the emission spectrum.The above was verified by carrying out radial velocity measurement experiments based on solar absorption lines.After presenting the optimal optical path difference expression for the absorption line,the influencing factors of the interference fringe contrast are analyzed.The numerical simulation results show that the deeper the absorption depth,the wider the line width,the greater the number of the absorption lines,and the narrower the filter bandwidth,the higher the interference fringe contrast.In order to optimize the structure of the DASH interferometer to obtain the maximum phase shift sensitivity,the optimal optical path difference calculation formulas for the emission line and absorption line are given.In order to achieve a highprecision measurement of the frequency shift of the absorption and the emission lines in the star spectrum,the two radial velocity extraction methods under the two spectral lines are unified,and the influencing factors of the interference fringe contrast from the absorption spectrum are analyzed.Our work has laid the foundation for DASH spectroscopy technology for autonomous astronomical navigation of deep space detectors.