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The Martian gravity field has been improved significantly in terms of resolution, with the spatial resolution rising to 100 km and accuracy increasing up to the 110 degree and order, assisted by data collected in Mars exploration missions like MGS, MRO, and Odyssey. However, as the tracking data used for the Martian gravity field solution are from...
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... addition, we show the gravity anomaly error distribu- tion in Figs. 2 and 3 to validate the improvements made in Martian gravity field models. The errors of the gravity anomaly are computed based on the Martian gravity field co- efficient variance-covariance matrix, obtained from the in- verse matrix of the normal matrix. This matrix can be used to generate the gravity anomaly and aeroid error by the er- ror ...
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... present the gravity anomaly distribution in Fig. 3. We only show the error of model P and model PSBI, as the dif- ference between model PC and model PSBI is indistinctive, so we do not present the error distribution of model PC. From Fig. 3 we can see that in both model P and model PSBI, there are strong error signals in the eastern part of Mars from 30 degree to 90 degree, possibly ...
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... present the gravity anomaly distribution in Fig. 3. We only show the error of model P and model PSBI, as the dif- ference between model PC and model PSBI is indistinctive, so we do not present the error distribution of model PC. From Fig. 3 we can see that in both model P and model PSBI, there are strong error signals in the eastern part of Mars from 30 degree to 90 degree, possibly because we do not use an exact circular orbit, and because the distribution of the tracking data is more sparse than other parts of Mars. We also find that at south and north Polar Regions, ...
Citations
... Dynamic orbit and gravity field determination theory (Tapley et al. 2004) is employed for lunar gravity field recovery and performed using LUGREAS (Ye et al. 2016), which was strictly validated with the GEODYN-II/SOLVE software packages (Pavlis et al. 2006;Ulman 1994). This software also has been adapted for use in Mars applications (Yan et al. 2017a(Yan et al. , 2017b. The method simultaneously estimates orbital elements, gravity field coefficients, and optional additional parameters such as the solar radiation coefficient or the lunar tidal Love number K 2 within a weighted least-squares adjustment (Lemoine et al. 1997). ...
The precision of lunar gravity field estimation has improved by means of three to five orders of magnitude since the successful GRAIL lunar mission. There are still discrepancies however, in the low degree coefficients and long wavelength components of the solutions developed by two space research centers (JPL and GSFC). These discrepancies hint at the possibilities for improving the accuracy in the long wavelength part of the lunar gravity field. In the near future, China will launch the Chang’E-5 lunar mission. In this sample-return mission, there will be a chance to do KBRR measurements between an ascending module and an orbiting module. These two modules will fly around lunar at an inclination of ∼49 degrees, with an orbital height of 100 km and an inter-satellite distance of 200 km. In our research, we simulated the contribution of the KBRR tracking mode for different GRAIL orbital geometries. This analysis indicated possible deficiencies in the low degree coefficient solutions for the polar satellite-to-satellite tracking mode at various orbital heights. We also investigated the potential contributions of the KBRR to the Chang’E-5 mission goal of lunar gravity field recovery, especially in the long wavelength component. Potential improvements were assessed using various power spectrums of the lunar gravity field models. In addition, we also investigated possible improvements in solving lunar tidal Love number K2. These results may assist the implementation of the Chang’E-5 mission.
The C20 and C22 coefficients of the Phobos gravity field are key parameters to constrain the internal structure of the Martian moon, but reliable observed values of these parameters are still missing. In this paper, we demonstrate, through a combination of forward and inverse modelling of simulated Doppler spacecraft tracking data collected from the Earth, that a Phobos flyby along a near polar Mars orbit is optimal when determining the C20 coefficient, and further, that a near equatorial flyby Mars orbit is optimal for determination of the C22 coefficient. Therefore, the combination of a near polar and a near equatorial orbit is an effective way to determine the Phobos C20 and C22 gravity field coefficients. This work provides a reference for a future Chinese Mars mission.
