Research On Measurement Error Calibration Technique Of Ground-based TT&C Systems

The ground-based TT&C system is an important part of China's space TT&C(Tracking,Telemetry and commanding)system.At present,to ensure the measurement accuracy of the ground-based TT&C system,the traditional error calibration method is used to calibrate and the measurement errors of the ground-based TT&C system.The traditional calibration method has two main problem.Firstly,even calibration with the traditional calibration methods,the residual measurement error of the TT&C system is still large.The residual range error is more than 10 meters and the residual velocity error is about 5 cm/s.Secondly,the traditional calibration methods,which have the shortcomings of small range and low dynamics,can not accurately refelect the measurement error characteristics of the TT&C system in actual space missons.To overcome the shortcomings of the traditional calibration methods,a new error calibration method,which is based on satellite-to-ground double-differential GPS,is proposed in this dissertation.This new error calibration method uses the nano-satellite as the calibration satellite to provide service for the measurement error calibration of the ground-based TT&C system.A spaceborne GPS receiver and a GPS receiver loaded on the ground TT&C station form a differential GPS measument system.This dissertation has systematically studied the real-time and the off-line satellite-to-ground baseline determination algorithms to solve the key issues about the high dynamic satellite-to-ground baseline,the weak correlation of common errors for satellite-to-ground differential GPS system,and the fixing strategy of carrier phase ambiguity resolution.On this basis,the measurement error model of the ground-based TT&C system and the solution method for the error model are also established,and then high precision error calibration results are obtained.To validate the new error calibration method for the ground-based TT&C system,a hardware-in-the-loop simulation platform is constructed by using dual-frequency GPS receivers and a SPIRENT GPS signal generator.The main work and contributions of this dissertation are as follows(1)To overcome the shortcomings of traditiaonal error calibration methods,a new measurement error calibration scheme based on satellite-to-ground baseline determination is designed and proposed.The error models of the TT&C system's ranging,velocity measurement and their solving methods are established.(2)Aiming at the problem to correct the GPS observation errors in the application scenario of satellite-to-ground baseline determination,the equivalent range errors of ephemeris error,ionospheric delay and tropospheric delay are quantitatively analyzed,and the correction methods of GPS observation errors are given.On this basis,the relative position dilution precision(RPDOP)is used to evaluate the satellite-to-ground baseline accuracy.(3)The data quality analysis and control methods of GPS receivers are systemaically studied.A pseude range gross error detection method,which based on the elevation selection and the first order difference of the pseudo range's LG combination,is established.The cycle slip detection ability of TurboEdit's improved method is analyzed.The improved method can accurately detect the small cycle slip of 1?2 cycle.The types of GPS receiver's clock jump is analyzed,and then a method based on the estimation of the receiver's clock bias is proposed for detecting and repairing the clock jump.In view of that the traditional carrier smoothing pseudorange method is susceptible to the ionospheric delay,a new carrier smoothing pseudorange method based on the ionospheric estimation is studied.(4)The off-line satellite-to-ground baseline determination algorithm and the measurement error calibration method of the TT&C system are analyzed and studied.The robust adaptive extended Kalman filter(ARKF)is adopted as the filtering strategy and the solution method of the robust adaptive factor and the observation noise 's equivalent variance-covariance matrix is derived.The carrier phase ambiguity resolution is the key to obtain high preicsion positioning and navigation results.A cascading integer resolution method based on the LAMBDA algorithm is proposed in this dissertation.In the process of the ARKF algorithm,the satellite-to-ground relative dynamic model and the dynamic tracking model of the GPS observation noise are established.In order to improve the satellite-to-ground baseline accuracy,a fixed-interval smoother is adopted.Finally,the measurement error calibration method of the TT&C system,which use the off-line satellite-to-ground baseline solution as the reference,is validated by a hardware-in-loop simulation.The results show that the relative position accuracy(3D rms)of satellite-to-ground baseline in post-processing is about 17 cm and the relative velocity accuracy(3D rms)is about 1 mm/s.Calibrated with the off-line error calibration method,the residual systematic error of range data is down to 15 cm,and the residual systematic error of velocity is down to 1 cm/s.(5)The real-time satellite-to-ground baseline determination algorithm and the measurement error calibration method of the TT&C system are deeply studied.The difference between the real-time satellite-to-ground baseline determination algorithm and the off-line baseline determination algorithm is analyzed,and the tropospheric delay estimation model for ground stations is also given.The measurement error calibration method of the TT&C system,which use the real-time satellite-to-ground baseline solution as the reference,is validated by a hardware-in-loop simulation.The results show that the relative position accuracy(3D rms)of real-time satellite-to-ground baseline determination is less than 1 m and the relative velocity accuracy(3D rms)is about 3 mm/s.calibrated with the real-time error calibration method,the residual systematic error of range data is down to 40 cm,and the residual systematic error of velocity is down to 1 cm/s.In summary,using a nano-satellite as the calibration satellite,this dissertation deeply studies the measurement error calibration method of the ground-based TT&C system based on real-time and off-line satellite-to-ground baseline determination algorithm,and carries out fully simulation verification.The results show that in off-line calibration,the residual systematic error of range data is down to 15 cm,and the residual systematic error of velocity is down to 1 cm/s.In real-time calibration,the residual systematic error of range data is down to 40 cm,and the residual systematic error of velocity is down to 1 cm/s.