For tracking spacecraft and performing radio science, the transformation between the proper time （τ） given by a clock carried onboard a spacecraft and the barycentric coordinate time （TCB） is investigated under I...For tracking spacecraft and performing radio science, the transformation between the proper time （τ） given by a clock carried onboard a spacecraft and the barycentric coordinate time （TCB） is investigated under IAU resolutions. In order to more clearly demonstrate manifestations of a physical model and improve computa- tional efficiency, an analytic approach is adopted. After numerical verification, it is confirmed that this method is adequate to describe a Mars orbiter during one year, and is particularly good at describing the influence from perturbing bodies. Further analyses demonstrate that there are two main effects in the transformation： the gravi- tational field of the Sun and the velocity of the spacecraft in the barycentric coordinate reference system. The combined contribution of these effects is at the level of a few sub-seconds.展开更多
In the context of the fact that Einstein＇s general relativity has become an inevitable part of deep space missions, we will extend previous works on relativistic transformation between the proper time ^- of a clock o...In the context of the fact that Einstein＇s general relativity has become an inevitable part of deep space missions, we will extend previous works on relativistic transformation between the proper time ^- of a clock onboard a spacecraft orbiting Mars and the Barycentric Coordinate Time （TCB） by taking the clock offset into ac- count and investigate its accessibility by Fourier analysis on the residuals after fitting the ^--TCB curve in terms of n-th order polynomials. We find that if the accuracy of a clock can achieve better than ~ 10-5 s or ~ 10-6 s （depending on the type of clock offset） in one year after calibration, the relativistic effects on the difference between 7- and TCB will need to be carefully considered.展开更多
When a satellite galaxy falls into a massive dark matter halo, it suffers from the dynamical friction force which drags it into the halo＇s center, where it finally merges with the central galaxy. The time interval be...When a satellite galaxy falls into a massive dark matter halo, it suffers from the dynamical friction force which drags it into the halo＇s center, where it finally merges with the central galaxy. The time interval between entry and merger is called the dynamical friction timescale （Tdf）. Many studies have been dedicated to deriving Tdf using analytical models or N-body simulations. These studies have obtained qualitative agreements on how Zdf depends on the orbital parameters, and the mass ratio between the satellite and the host＇s halo. However, there are still disagreements on deriving an accurate form for Tdf. We present a semi-analytical model to predict Tdf and we focus on interpreting the discrepancies among different studies. We find that the treatment of mass loss from the satellite by tidal stripping dominates the behavior of Tdf. We also identify other model parameters which affect the predicted Tdf.展开更多
Einstein＇s general relativity （GR） has become an inevitable part of deep space missions. According to the International Astronomical Union （IAU） Resolutions which are built in the framework of GR, several time sc...Einstein＇s general relativity （GR） has become an inevitable part of deep space missions. According to the International Astronomical Union （IAU） Resolutions which are built in the framework of GR, several time scales and reference systems are recommended to be used in the solar system for control, navigation and scientific op- eration of a spacecraft. Under the IAU Resolutions, we derive the transformations be- tween global and local velocities of an arbitrary orbiter. These transformations might be used in orbit determination with Doppler tracking and prediction of Doppler ob- servables for the spacecraft. Taking the YingHuo-1 Mission as a technical example of future Chinese Mars explorations, we evaluate the significance and contributions of various components in the transformations. The largest contribution of the relativistic parts in the transformations can reach the level of ～ 5 × 10-5 m s^-1. This suggests that, for such a spacecraft like we have assumed, if the accuracy of Doppler tracking is better than ～ 5 × 10-5 m s^-1 then the relativistic parts of the transformations of velocities will be required.展开更多
基金funded by the National Natural Science Foundation of China (Grant Nos. 11103085 and 11178006)
文摘For tracking spacecraft and performing radio science, the transformation between the proper time （τ） given by a clock carried onboard a spacecraft and the barycentric coordinate time （TCB） is investigated under IAU resolutions. In order to more clearly demonstrate manifestations of a physical model and improve computa- tional efficiency, an analytic approach is adopted. After numerical verification, it is confirmed that this method is adequate to describe a Mars orbiter during one year, and is particularly good at describing the influence from perturbing bodies. Further analyses demonstrate that there are two main effects in the transformation： the gravi- tational field of the Sun and the velocity of the spacecraft in the barycentric coordinate reference system. The combined contribution of these effects is at the level of a few sub-seconds.
基金Supported by the National Natural Science Foundation of China
文摘In the context of the fact that Einstein＇s general relativity has become an inevitable part of deep space missions, we will extend previous works on relativistic transformation between the proper time ^- of a clock onboard a spacecraft orbiting Mars and the Barycentric Coordinate Time （TCB） by taking the clock offset into ac- count and investigate its accessibility by Fourier analysis on the residuals after fitting the ^--TCB curve in terms of n-th order polynomials. We find that if the accuracy of a clock can achieve better than ~ 10-5 s or ~ 10-6 s （depending on the type of clock offset） in one year after calibration, the relativistic effects on the difference between 7- and TCB will need to be carefully considered.
基金funded by the National Natural Science Foundation of China (Grant No. 10573028)the Key Project (Grant No. 10833005)+4 种基金the Group Innovation Project (Grant No. 10821302)the National Basic Research Program of China (973 ProgramNo. 2007CB815402)supported by the One Hundred Talents Project of the Chinese Academy of Sciencesthe foundation for the authors of CAS excellent doctoral dissertations
文摘When a satellite galaxy falls into a massive dark matter halo, it suffers from the dynamical friction force which drags it into the halo＇s center, where it finally merges with the central galaxy. The time interval between entry and merger is called the dynamical friction timescale （Tdf）. Many studies have been dedicated to deriving Tdf using analytical models or N-body simulations. These studies have obtained qualitative agreements on how Zdf depends on the orbital parameters, and the mass ratio between the satellite and the host＇s halo. However, there are still disagreements on deriving an accurate form for Tdf. We present a semi-analytical model to predict Tdf and we focus on interpreting the discrepancies among different studies. We find that the treatment of mass loss from the satellite by tidal stripping dominates the behavior of Tdf. We also identify other model parameters which affect the predicted Tdf.
基金Supported by the National Natural Science Foundation of China
文摘Einstein＇s general relativity （GR） has become an inevitable part of deep space missions. According to the International Astronomical Union （IAU） Resolutions which are built in the framework of GR, several time scales and reference systems are recommended to be used in the solar system for control, navigation and scientific op- eration of a spacecraft. Under the IAU Resolutions, we derive the transformations be- tween global and local velocities of an arbitrary orbiter. These transformations might be used in orbit determination with Doppler tracking and prediction of Doppler ob- servables for the spacecraft. Taking the YingHuo-1 Mission as a technical example of future Chinese Mars explorations, we evaluate the significance and contributions of various components in the transformations. The largest contribution of the relativistic parts in the transformations can reach the level of ～ 5 × 10-5 m s^-1. This suggests that, for such a spacecraft like we have assumed, if the accuracy of Doppler tracking is better than ～ 5 × 10-5 m s^-1 then the relativistic parts of the transformations of velocities will be required.
