Mars Express tracking and orbit determination trials with Chinese VLBI network

Cao, Jianfeng; Huang, Yiwen; Hu, Xiaogong; Ma, Maoli; Zheng, Weimin

doi:10.1007/s11434-010-4170-8

Cited by 24 publications

(19 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It can be seen from Table-3 that the pH of neutral and weakly alkaline (pH 6.99-7.71) leachate correlates rarely to a variety of heavy metals, merely negatively to Pb at level of 0.05. This may be ascribed to that although activated lead minerals constantly dissolved during soaking, the dissolved trace heavy metal Pb was converted into hydroxide precipitate 27 in neutral or weakly alkaline solution, or adsorbed by colloidal iron and organics in residual skeleton, or forming secondary minerals of trace heavy metals, resulting in decreasing Pb concentration in leachate as leachate tended to be slightly alkaline. Leachate pH is positively correlated to Cr, indicating that as the pH increases, migration capacity of Cr-containing compounds in leachate increases, facilitating the solubilization release of Cr-containing minerals.…”

Section: Resultsmentioning

confidence: 99%

Study on Geochemical Behaviour of Gangue Potential Acidic Release

Sun¹,

Shen²,

Duan³

et al. 2014

Asian J. Chem.

View full text Add to dashboard Cite

Geochemical behaviour of gangue potential acidic release has been investigated through soaking experiments under different conditions of liquid/solid ratio and soaking period. The results show that leachate pH ranges 6.99-7.71 (neutral or weakly alkaline) during immersion test which lasted for 30 days. The closed state where soaking test was performed inhibited the oxidation and dissolution of sulfur minerals containing in coal gangue, thereby affecting acidic release of gangue and making leachate weakly alkaline, resulting in only a small number of heavy metals Co, Cu, Mn and Sr at exchangeable state dissolved by water (dissolution rate ≤ 62.79 %) with the exception of Cr (completely dissolved) in gangue soaking. Under alkaline conditions, dissolution rates of Co, Cr, Cu, Mn and Sr carbonates, iron and manganese oxide phase, organics matter and residual are extremely low (≤ 16.67 %). During soaking test, dissolution release rates of sulfur containing minerals in gangue with acid production (H2SO4) capacity of 57.56 Kg/t range merely 2.70-10.34 %. Along with the proceeding of soaking, enhancement of dissolution-release rate of sulfur containing minerals will lead to the solubilization-release of harmful trace elements in gangue. Hence, acidic release of gangue has a potentially considerable impact on environment.

show abstract

Section: Resultsmentioning

confidence: 99%

Study on Geochemical Behaviour of Gangue Potential Acidic Release

Sun¹,

Shen²,

Duan³

et al. 2014

Asian J. Chem.

View full text Add to dashboard Cite

show abstract

“…Both of the differenced ranges observations and the VLBI observations are the difference measurement [3]. Therefore differenced ranges as VLBI can provide a constraint in the transverse direction of satellite orbit.…”

Section: Principle Of Differenced Ranges Between Master Station and Smentioning

confidence: 99%

Satellite orbit determination combining C-band ranging and differenced ranges by transfer

Yang

Chen

2013

Chin. Sci. Bull.

View full text Add to dashboard Cite

The constraint in the transverse direction of satellite orbit with differenced ranges between master station and slave stations by transfer as an angular observation data is explained in theory. Differenced ranges in combination with C-band ranging by transfer were used in satellite orbit determination. The position error of overlapped orbit differences for combining is less than that for ranging only. The residual of predicted orbit forward 5.5 days for combining is 3.1762 m, while the residual for ranging only with the same duration is 3.5380 m. Both the orbital overlapping and orbit prediction experimentations can testify the constraint in the transverse direction of satellite orbit with differenced ranges, and the results show that the accuracy of orbit determination and orbit prediction is improved by combining differenced ranges and C-band ranging. The space segment of satellite navigation system of China consists of several geostationary Earth orbit (GEO) satellites. The orbit accuracy of GEO satellites has an influence on positing capability of navigation system directly. Therefore, the research on precise orbit determination of GEO satellites has a great significance. "Determination of satellite orbit by transfer" was developed by the National Time Service Center, Chinese Academy of Sciences. Owing to the high orbit determination accuracy, the system is suitable for GEO satellite tracking [1]. The accuracy of C-band ranging is better than one centimetre in the direction of line-of-sight. The GEO satellite is placed at an altitude of 36000 km above the equator. The angle of GEO satellite to the ranging stations is only a few degrees. The ranging data is unable to provide constrain in the transverse direction of the satellite orbit owing to the poor observation geometry.The observation mode of differenced ranges by transfer is the development for C-band ranging by transfer. The principle of the observation mode of differenced ranges is the same as very long baseline interferometry (VLBI). It can provide strongly constrain in the transverse direction of the satellite orbit, perpendicular to the line-of-sight. The improvement of orbit prediction accuracy combining differenced ranges and ranging by transfer has been implemented with short-arc data [2].In order to explaining the constraint in the transverse direction of satellite orbit by differenced ranges in theory, the relation between the measurement error of angular observation and satellite orbit is analyzed in detail. The experiments of orbital overlapping and orbit prediction are carried out to validate the improvement in accuracy of orbit determination and prediction with differenced ranges.

show abstract

“…Furthermore, considering that the distance between the lander and the earth is far, it is necessary to build the observation model in the barycentric celestial reference, and the related coordinate time is TDB. The influence of general relativity should be considered [12].…”

Section: Equations Of Observationsmentioning

confidence: 99%

Precise positioning of the Chang’E-3 lunar lander using a kinematic statistical method

Huang

et al. 2012

Chin. Sci. Bull.

Self Cite

View full text Add to dashboard Cite

A kinematic statistical method is proposed to determine the position for Chang'E-3 (CE-3) lunar lander. This method uses both ranging and VLBI measurements to the lander for a continuous arc, combing with precise knowledge about the motion of the moon as provided by planetary ephemeris, to estimate the lander's position on the lunar surface with high accuracy. Accuracy analyses are carried out with simulation data using the software developed at Shanghai Astronomical Observatory in this study to show that measurement errors will dominate the position accuracy. Application of lunar digital elevation model (DEM) as constraints in the lander positioning is also analyzed. Simulations show that combing range/doppler and VLBI data, single epoch positioning accuracy is at several hundred meters level, but with ten minutes data accumulation positioning accuracy is able to be achieved with several meters. Analysis also shows that the information given by DEM can provide constraints in positioning, when DEM data reduce a 3-dimensional positioning problem to 2-dimensional. Considering the Sinus Iridum, CE-3 lander's planned landing area, has been observed with dedicated details during the CE-1 and CE-2 missions, and its regional DEM model accuracy may be higher than global models, which will certainly support CE-3's lander positioning. The first Chinese lunar explorer CE-1 was launched on October 24, 2007, and following CE-2 was launched on October 1, 2010 [1][2][3]. According to the long-term schedule, Chinese unmanned lunar exploration plan is divided into three stages: orbiting, landing and returning stages. In the orbiting stage, the CE-1 and CE-2 satellites fly around the moon and take photos about the landing area. In the landing stage, the main task is to softland on the lunar surface and to explore automatically [4]. A lunar lander and a rover are needed in this stage. How to determine the positions of the lander and rover on the lunar surface is very important to the following Chinese lunar exploration project. The rover moves very slowly and not far away from the lander, so the position determination of the lander is more critical. Dealing with position determination of a satellite, the dynamic statistical orbit determination (OD) method and single point positioning are widely used in lunar exploration [1][2][3]5,6]. OD can be viewed as a special case of general parameter estimation problem, where the parameters characterizing the orbit of a satellite, have to be determined from observations using the least squares method. The main error sources are from observations as well as the force model, and in order to get high OD accuracy, forces exerting on the satellite must be modeled precisely. Comparing with dynamic OD method, single point positioning does not need to model forces, and the position of the satellite can be

show abstract

Mars Express tracking and orbit determination trials with Chinese VLBI network

Cited by 24 publications

References 15 publications

Study on Geochemical Behaviour of Gangue Potential Acidic Release

Study on Geochemical Behaviour of Gangue Potential Acidic Release

Satellite orbit determination combining C-band ranging and differenced ranges by transfer

Precise positioning of the Chang’E-3 lunar lander using a kinematic statistical method

Contact Info

Product

Resources

About