TY - JOUR

T1 - Magnetic torquer induced disturbing signals within GRACE accelerometer data

AU - Peterseim, Nadja

AU - Flury, Jakob

AU - Schlicht, Anja

N1 - Funding Information: First of all we would like to thank the Center for Space Research (CSR) of the University of Texas at Austin for supplying us with the 10 Hz accelerometer data this work is basically based upon. Additionaly, the work of Gerhard Kruizinga for his program for correction of the time-tags of the accelerometer data is greatly acknowledged. Also, we would like to thank Helmholtz–Zentrum Potsdam, Deutsches GeoForschungsZentrum (GFZ) and the Jet Propulsion Laboratory (JPL) for supplying us with Level 1b data via their data centers ISDC and PO.DAAC. Furthermore, we would like to thank Daniel Bindel from ZARM Bremen for providing technical information on the magnetic torquers. The Bundesministerium für Bildung und Forschung (BMBF, German Federal Ministry of Education and Research) is acknowledged for financial support of this study within the Lotse-CHAMP/GRACE project (03G0728C) of the GEOTECHNOLOGIEN Programme.

PY - 2012/5/1

Y1 - 2012/5/1

N2 - The GRACE (Gravity Recovery And Climate Experiment) gravity field satellite mission was launched in 2002. Although many investigations have been carried out, not all disturbances and perturbations upon satellite instruments and sensors are resolved yet. In this work the issue of acceleration disturbances onboard of GRACE due to magnetic torquers is investigated and discussed. Each of the GRACE satellites is equipped with a three-axes capacitive accelerometer to measure non-gravitational forces acting on the spacecraft. We used 10 Hz Level 1a raw accelerometer data in order to determine the impact of electric current changes on the accelerometer. After reducing signals which are induced by highly dominating processes in the low frequency range, such as thermospheric drag and solar radiation pressure, which can easily be done by applying a high-pass filter, disturbing signals from onboard instruments such as thruster firing events or heater switch events need to be removed from the previously filtered data. Afterwards the spikes which are induced by the torquers can be very well observed. Spikes vary in amplitude with respect to an increasing or decreasing current used for magnetic torquers, and can be as large as 20 nm/s 2 . Furthermore, we were able to set up a model for the spikes of each scenario with which we were able to compute model spike time series. With these time series the spikes can successfully be removed from the 10 Hz raw accelerometer data. Spectral analysis of the time series reveal that an influence onto gravity field determination due to these effects is very unlikely, but can theoretically not be excluded.

AB - The GRACE (Gravity Recovery And Climate Experiment) gravity field satellite mission was launched in 2002. Although many investigations have been carried out, not all disturbances and perturbations upon satellite instruments and sensors are resolved yet. In this work the issue of acceleration disturbances onboard of GRACE due to magnetic torquers is investigated and discussed. Each of the GRACE satellites is equipped with a three-axes capacitive accelerometer to measure non-gravitational forces acting on the spacecraft. We used 10 Hz Level 1a raw accelerometer data in order to determine the impact of electric current changes on the accelerometer. After reducing signals which are induced by highly dominating processes in the low frequency range, such as thermospheric drag and solar radiation pressure, which can easily be done by applying a high-pass filter, disturbing signals from onboard instruments such as thruster firing events or heater switch events need to be removed from the previously filtered data. Afterwards the spikes which are induced by the torquers can be very well observed. Spikes vary in amplitude with respect to an increasing or decreasing current used for magnetic torquers, and can be as large as 20 nm/s 2 . Furthermore, we were able to set up a model for the spikes of each scenario with which we were able to compute model spike time series. With these time series the spikes can successfully be removed from the 10 Hz raw accelerometer data. Spectral analysis of the time series reveal that an influence onto gravity field determination due to these effects is very unlikely, but can theoretically not be excluded.

KW - Accelerometer

KW - GRACE

KW - Magnetic Torquers

UR - http://www.scopus.com/inward/record.url?scp=84859006274&partnerID=8YFLogxK

U2 - 10.1016/j.asr.2012.02.013

DO - 10.1016/j.asr.2012.02.013

M3 - Article

AN - SCOPUS:84859006274

VL - 49

SP - 1388

EP - 1394

JO - Advances in space research

JF - Advances in space research

SN - 0273-1177

IS - 9

ER -