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A readout circuit with high sensitivity and high linearity is proposed in this paper. The applied pressure is sensed by Wheatstone bridge which can reduce the adverse effect of temperature. As the applied pressure changes from 15kPa to 115kPa, the sensitivity of the bridge is 0.36mV/kPa. The current source of the circuit can provide a current with a positive coefficient which can compensate for the inherent high-temperature loss of sensitivity of the Piezoresistive Bridge. Three high-precision operational amplifiers with symmetrical input and rail-to-rail output are used to process the output signal of the bridge. It can provide high CMRR with 123.8dB, open loop gain is 110dB and the output swings from 36.41mV to 4.953mV as the power supply is 5V. A thin film resistors network can compensate for the zero pressure offset and sensitivity by trimming. The high sensitivity of the bridge and the high linearity of the proposed circuit make the readout circuit suitable for monolithically integrated pressure sensor.

The GOCE Earth's gravitational field complete up to degree and order 250 is recovered based on the time-space-wise-approach associated with Kaula regularization in order to study the influences of satellite gravity gradiometry on the accuracy of medium-high frequency Earth's gravitational field recovery. The simulated results show: Firstly, the time-space-wise-approach is an effective way to accurately and rapidly determine the high-degree Earth's gravitational field; Secondly, the Kaula regularization is one of the key processes to reduce ill condition of normal matrix; Thirdly, the large-scale linear system of equations is solved quickly using the improved pre-conditioned conjugate-gradient iterative approach, and the computing speed can be improved at least 1000 times as compared to the direct least-squares approach; Fourthly, at the degree 250, cumulative geoid height and gravity anomaly errors are 9. 295 cm and 0. 204 mGal with orbital error 1 cm and gravity gradient error 3 X 10(-12)/s(2), respectively. Finally, the complementarity of high-accuracy and high-resolution Earth's gravitational field recovery between international GRACE and GOCE missions is demonstrated.

Based on the semi-analytical method and using the combined model whose accuracy on the accumulative geoid is influenced by the error of the inter-satellite velocity of the GRACE (Gravity Recovery and Climate Experiment) binary in the K band, the orbital error of the GPS receiver and the error of the non-conservative force of the accelerometer, we have for the first time carried out an analysis on the requirements of the orbital parameters in the SST (satellite-to-satellite tracking) mode. We suggest that it would be better for the first gravity satellite of our country the average orbital altitude and inter-satellite distance will be designed, respectively, as 400 km and 220 km. This study may not only provide a theoretical basis and calculational guarantee for the optimal selection of the orbital parameters in the program of satellite gravimetry of our country in the future as well as the efficient and quick estimation of the accuracy of the global gravitational field, but also possess certain guiding significance on the orientation of the development of the future international programs of the GRACE Follow-On terrestrial gravimetry and the GRAIL (Gravity Recovery and Interior Laboratory) lunar gravitational exploration.

The seasonal variation of atmosphere, ocean, and continent water masses causes variation in surface deformation, which is detectable using Gravity Recovery and Climate Experiment (GRACE) and GPS observations. In comparison with the surface deformation simulated with atmosphere, ocean, and land water models, the deformation derived from GRACE has no errors related to the accuracy uncertainties of the models. In this paper the climate-driven seasonal vertical deformation of the solid Earth in China and neighboring areas is calculated from GRACE monthly time-variable gravity field coefficients truncated to degree and order 60, and the results are compared with seasonal signals measured at 42 GPS sites in the same region. In the calculation we use de-stripe filtering and de-stripe plus 3×105 m Gaussian smoothing respectively, and we find that the former filtering result is better than the latter one. Computing the annual vertical crustal deformation from GRACE using de-stripes, we find that at all GPS sites the amplitudes and phases of deformation from GRACE are close to those from GPS observations. Obvious discrepancy at some sites suggests that it might be caused by a local geophysical process or GPS site analysis error and GPS time series discontinuity. In the mainland of China and adjacent areas the smallest amplitude of deformation is about 1 × 10−3 m in the southeast of station TASH and the greatest is 10 × 10−3 m in the region of Ganges-Lancang River Basin. These results demonstrate that GRACE can be a new effective tool for monitoring large-scale annual vertical deformation of the solid Earth in China and adjacent areas.

The accuracy of Earth's gravitational field from the Gravity Recovery and Climate Experiment (GRACE) Follow-On satellite mission is efficiently and rapidly estimated for the first time based on the analytic method. Firstly, the new single and combined analytic error models of cumulative geoid height influenced by four error sources including the intersatellite range-rate of interferometric laser ranging system, orbital position and velocity of GPS receiver and nonconservative force of accelerometer from GRACE Follow-On satellites are established using the power spectrum principle, respectively. Secondly, the dependability of analytic error model is validated according to the consistency of the matching accuracy indexes of GRACE key payloads from the single analytic error models and the GRACE Level 1B provided by the American Jet Propulsion Laboratory (JPL), and the conformity of GRACE cumulative geoid height errors from the combined analytic error model and the Earth's gravitational field model EIGEN-GRACE02S released by the German GeoForschungsZentrum Potsdam (GFZ). Finally, the influences of different matching accuracy indexes of key payloads and orbital altitudes of GRACE Follow-On satellites on the accuracies of Earth's gravitational field are demonstrated contrastively. At the 360 degree, cumulative geoid height error is 1.231×10−1 m using combined analytic error model based on orbital altitude 250 km, intersatellite range 50 km, intersatellite range-rate error 1×10−9 m/s, orbital position error 3×10−5 m, orbital velocity error 3×10−8 m/s and nonconservative force error 3×10−13 m/s2. This work not only can provide the theoretical foundation and calculational guarantee for the efficient and rapid determination of the accuracies of current GRACE and future GRACE Follow-On Earth's gravitational field, but also has some reference significance to the successful execution of the future Gravity Recovery and Interior Laboratory (GRAIL) lunar satellite gravity exploration mission.

The matching relationship of accuracy indexes from GRACE accelerometer, K-band ranging system and GPS receiver is demonstrated by numerical simulation based on the improved energy conservation principle. The results show: Firstly, cumulative geoid height error comes to 19~80 cm and 1.5°× 1.5° cumulative gravity anomaly error is at the level of 0.3~1.3 mGal at degree 120, when the resolution of accelerometer is designed as ACCX = (1 ~ 10) × 10−9 m/s2 and ACCY,Z = (1 ~ 10) × 10−10 m/s2 combined with other payloads with the same accuracy indexes of GRACE; Secondly, it is appropriate to set the three-axis resolutions of accelerometer as ACCX = (1 ~ 5) × 10−9 m/s2 and ACCY,Z = (1 ~ 5) × 10−10 m/s2 in the future satellite gravity measurement in China, which basically matches with GRACE other payloads.

Firstly, the GRACE Level 1B measured data including the orbital position and velocity of GPSreceiver, intersatellite range rate of K-band ranging system, nonconservative force of accelerometer and attitudeof star camera assembly between 2007-06-01∼2007-12-31 provided by the American Jet Propulsion Laboratory(JPL) are processed effectively by orbital connection, gross error detection, linear interpolation, recalibration,coordinate transformation, error analysis, and so on. Secondly, the GRACE Earth’s gravitational field completeup to degree and order 120 is recovered based on the improved energy conservation principle, the cumulativegeoid height error is 25.313 cm at degree 120. Finally, the dependability of the Earth’s gravitational field modelIGG-GRACE is verified in the paper, and the reasons why the accuracy of IGG-GRACE is a little superior to theEarth’s gravitational field model EIGEN-GRACE02S provided by the German GeoForschungsZentrum Potsdam(GFZ) in the low frequency range and is slightly lower than that in the medium-high frequency band are analyzed.Key words GRACE, Key payloads, Measured data, Energy conservation principle, Earth’s gravitational field

The demonstration of simulative study on the accuracy of Earth's gravitational field influenced by the different adjusted accuracy of center of mass between GRACE satellite and SuperSTAR accelerometer proof mass is carried out using the improved energy conservation principle. The results show: Firstly, at degree 120, cumulative geoid height error is at the level of 17.616 cm with the adjusted accuracy of center of mass designed as 0 m, and errors come to 18.106 cm, 19.033 cm and 27.329 cm with the adjusted accuracy designed as 5×10−5 m, 1×10−4 m and 5×10−4 m, respectively. Secondly, under standard of measured cumulative geoid height error from the Earth's gravitational field model EIGEN-GRACE02S publicized by German GFZ, the adjusted accuracy of center of mass designed as (5~10)×10−5 m is matched with the accuracy of GRACE key payloads including Kband ranging system, GPS receiver, SuperSTAR accelerometer and Star camera assembly, and does not influence the accuracy of Earth's gravitational field. Therefore, we propose that the optimal adjusted accuracy of center of mass between GRACE satellite and SuperSTAR accelerometer proof mass is designed as (5~10)×10−5 m in the future first gravity satellite in China.

In this paper, firstly, the new combined error model of cumulative geoid height influenced by three error sources including the inter-satellite range-rate of K-band ranging system, orbital position of GPS receiver and non-conservative force of accelerometer from GRACE satellites is established using the semi-analytical method. Secondly, the dependability of error models is demonstrated based on matching relationship among the accuracy indexes of key payloads. Finally, the accuracy of global gravitational field up to degree and order 120 is effectively and rapidly estimated from GRACE Level 1B measured observation errors of the year 2006 publicized by the Jet Propulsion Laboratory (JPL) in the USA, and the cumulative geoid height error is 18.368 cm at degree 120, which preferably accords with the Earth's gravitational field model EIGEN-GRACE02S provided by the Geo-ForschungsZentrum Potsdam (GFZ) in Germany. This work can provide theoretical foundation and calculational guarantee for the efficient and rapid estimation of the accuracy of high-degree global gravitational field model in the future international satellite gravity measurement mission (e.g. GRACE Follow-On, degree 360).

Using the CSR4.0 global ocean tidal model and the local ocean tidal maps of China Seas, we calculated the ocean tidal displacement corrections for the Earth Crust Movement Network of China. We also discuss the effect on the corrections caused by the tidal model and Green's function. As an actual example, we used the GPS observational data to estimate the influence of ocean loading tides on the GPS baseline vectors. Our results show that the corrections of ocean loading tide for the site displacement of geodetic stations and the variation of GPS baseline vector may reach maximum values of about 2 cm and 2 mm, respectively.

With the development of space-geodesy and the application of GPS and SLR in geodesy, the studies on geocenter variation become more important. In the paper, we discuss the geocenter variation in three aspects: definition, theory and observation. Comparing the calculated geocenter variation with the observable result from SLR, we conclude that the geocenter variation has obvious annual and diurnal period with the amplitudes of 2–6mm, which should be corrected in high-precision geodesy.

An Earth's gravity field model IGGGRACE01S has been derived from 141 days of GRACE tracking data, including K-band, accelerometer, satellite orbit data. The model resolves the geoid with an accuracy of about 0.012m at a resolution of 500km half-wavelength, it improves the accuracy of the gravity field model in the long- to medium-wavelength part ( < 80 degree) than pre-CHAMP model. Comparing the coefficients of IGGGRACE01S, EIGEN-GRACE02S, EIGEN-CHAMP03S, and EGM96 models, the result shows that the coefficients of IGGGRACE01S are close to those of EIGEN-GRACE02S, and much different to those of the other two models. Comparing the geoid undulations and gravity anomalies derived from the above-mentioned models, the results indicate that the IGGGRACE01S solution is close to EIGEN-GRACE02S solution, and there exist large differences between IGGGRACE01S and EGM96 in Antarctica region. Comparing the gravity anomalies derived from IGGGRACE01S (72 degree) with NIMA gravity anomalies data (2.5 degrees x 2.5 degrees), the standard deviation is 4.8 mGal in China land region.

Objective To explore mechanisms of acupuncture for reducing of body weight. Methods The rat obesity model was developed by subcutaneous injection of sodium glutamate solution, and the experimental rats were divided into a blank control group, a model group, an electroacupuncture group and a sibutramine group( blood TC, TG, HDL-C, LDL-C contents and lipoprotein lipase (LPL) activity , and serum leptin and insulin levels were determined. Results The body weight and Lee's index, and TG, TC and LDL-C contents in the electroacupuncture group decreased significantly as compared with those in the model group (all P0. 01), the actions in the electroacupuncture group being superior to those in the sibutramine group; the HDL-C contents in both the electroacupuncture and the sibutramine groups were higher than that of the model group (P0. 01) with no significant difference between the electroacupuncture group and the sibutramine group; LPL activity in the electroacupuncture group increased significantly as compared with that in the model group (P0. 01); serum leptin and insulin levels in both the electroacupuncture group and the sibutramine group were lower than that in the model group (P0.05, P 0. 01), with no significant difference between the electroacupuncture group and the sibutramine group in the effect on insulin content, and the decrease of leptin level in the electroacupuncture group was more as compared with the sibutramine group (P0. 01). Conclusion Electroacupuncture can improve the status of high blood lipids, increase lipoprotein lipase activity, and regulate serum leptin and insulin levels in the obestic rat.