GOCE kinematic orbit adjustment for EGM validation and accelerometer calibration

The main principle and mathematical model of GOCE kinematic orbit adjustment for Earth gravity field model （EGM） validation and accelerometer calibration are presented. Based on 60 days GOCE kinematic orbits with 1-2 cm accuracy and accelerometer data from 2009-11-02 to 2009-12-31, the RMS-of-fit （ROF） of them using EGM2008, EIGEN-SC, ITG- GRACE2010S and GOCO01S up to 120, 150 and 180 degree and order （d/o） are evaluated and compared. The scale factors and biases of GOCE accelerometer data are calibrated and the energy balance method （EBM） is performed to test the accuracy of accelerometer calibration. The results show that GOCE orbits are also sensitive to EGM from 120 to 150 d/o. The ROFs of EGMs with 150 and 180 d/o are obviously better than those of EGMs with 120 d/o. The ROFs of GOCO01S and ITG-GRACE2010S are almost the same up to 120 and 150 d/o, which are about 3.3 cm and 1.8 cm, respectively. They are far better than those of EGM2008 and EIGEN-SC with the same d/o. The ROF of GOCO01S with 180 d/o is about 1.6 em, which is the best one among those EGMs. The accelerometer calibration accuracies （ACAs） of ITG-GRACE2010S and GOCO01S are obviously higher that those of EGM2008 and EIGEN-SC. The ACA of GOCO01S with 180 d/o is far higher than that of EGMs with 120 d/o, and a little higher than that of ITG-GRACE2010S with 150 d/o. I t is suggested that the newest released EGM such as GOCO01S or GOCO02S till at least 150 d/o should be chosen in GOCE precise orbit determination （POD） and accelerometer calibration.

A Survey of Error Analysis and Calibration Methods for MEMS Triaxial Accelerometers

MEMS accelerometers are widely used in various fields due to their small size and low cost,and have good application prospects.However,the low accuracy limits its range of applications.To ensure data accuracy and safety we need to calibrate MEMS accelerometers.Many authors have improved accelerometer accuracy by calculating calibration parameters,and a large number of published calibration methods have been confusing.In this context,this paper introduces these techniques and methods,analyzes and summarizes the main error models and calibration procedures,and provides useful suggestions.Finally,the content of the accelerometer calibration method needs to be overcome.

Calibration of GRACE on-board accelerometers for thermosphere density derivation

Low Earth Orbit satellite on-board accelerometers play an important role in improving our understanding of thermosphere density;however,the accelerometer-derived densities are subject to accelerometer calibration errors.In this study,two different dynamic calibration schemes,the accelerometer parameter-incorporated orbit fitting and precise orbit determination(POD),are investigated with the Gravity Recovery And Climate Experiment(GRACE)satellite accelerometers for thermosphere density derivation during years 2004–2007(inclusive).We show that the GRACE accelerometer parametrization can be optimized by fixing scale coefficients and estimating biases every 60 min so that the orbit fitting and POD precision can be improved from 10 cm to 2 cm in the absence of empirical acceleration compensations and as a result the integrity of calibration parameters may be reserved.The orbit-fitting scheme demonstrates similar calibration precision with respect to POD.Their bias estimates in the along-track and cross-track components exhibit an offset within 0.1%and a standard deviation(STD)less than 0.3%.Correspondingly,a bias of 2.20%and a STD of 5.75%exists between their thermosphere density estimates.The orbit-fitting and POD-derived thermosphere densities are validated through the comparison against the results published by other institution.The comparison shows that either of them can achieve a precision level at 6%.To derive thermosphere density from the rapid-increasing amount of on-board accelerometer data sets,it is suggested to take full advantage of the orbit-fitting scheme due to its high efficiency as well as high precision.