نوع مقاله : مقاله تحقیقی (پژوهشی)
1 Assistant Professor, Department of Surveying Engineering, Arak University of Technology, Arak, Iran
2 Associate Professor, School of Surveying and Geospatial Engineering, College of Engineering, University of Tehran,Tehran, Iran
عنوان مقاله [English]
The Gravity Recovery and Climate Experiment (GRACE) mission and its successor, GRACE Follow-On, have been observing the Earth’s static and time-variable gravity ﬁeld with unprecedented accuracy from 2002, thanks to the precision equipment used, such as very accurate ranging systems, dual-frequency GPS receivers, star cameras and highly sensitive accelerometers. The accelerometers on board of these missions provide high quality measurements of the non-gravitational forces acting on the satellites, provided that they are calibrated. In this paper, a wavelet-based detrending scheme is used to estimate drift and bias of GRACE accelerometer data. This method is applied to a simulated noisy time series and two sets of GRACE accelerometer data (recorded on January 1, 2005 and during March 2015). The results confirm the speed and ease of the proposed method due to the nature of the wavelet-based detrending scheme. The estimated bias and drift parameters have acceptable accuracies because the wavelet-based method does not require any reference value and its results are not affected by uncertainties in gravitational field modeling. Furthermore, some computational problems such as the amplification of noise during the numerical differentiation of satellite positions do not exist. In addition, the accelerometer readouts, provided in the Science Reference Frame (SRF), may be calibrated without applying any coordinate transformation.