Characteristics and accuracies of the GRACE inter-satellite pointing

authored by: Tamara Bandikova, Jakob Flury, Ung Dai Ko
Abstract: For almost 10 years, the Gravity Recovery and Climate Experiment (GRACE) has provided information about the Earth gravity field with unprecedented accuracy. Efforts are ongoing to approach the GRACE baseline accuracy as there still remains an order of magnitude between the present error level of the gravity field solutions and the GRACE baseline. At the current level of accuracy, thorough investigation of sensor related effects is necessary as they are one of the potential contributors to the error budget. In the science mode operations, the twin satellites are kept precisely pointed with their KBR antennas towards each other. It is the task of the onboard attitude and orbit control system (AOCS) to keep the satellites in the required formation. We analyzed long time series of the inter-satellite pointing variations as they reflect the AOCS performance and characteristics. We present significant systematic effects in the inter-satellite pointing and discuss their possible sources. Prominent features are especially related to the magnetic torquer characteristics, star cameras' performance and KBR antenna calibration parameters. The relation between the magnetic torquer attitude control and the Earth magnetic field, impact of the different performance of the two star camera heads on the attitude control and the features due to uncertainties in the calibration parameters relating the star camera frame to K-frame are discussed in detail. Proper understanding of these effects will help to reduce their impact on the science data and subsequently increase the accuracy of the gravity field solutions. Moreover, understanding the complexity of the onboard system is essential not only for increasing the accuracy of the GRACE data but also for the development of the future gravity field satellite missions.
Organisation(s): Institute of Geodesy
Quest: Centre for Quantum Engineering and Space-Time Research
External Organisation(s): University of Texas at Austin
Type: Article
Journal: Advances in space research
Volume: 50
Pages: 123-135
No. of pages: 13
ISSN: 0273-1177
Publication date: 01.07.2012
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: Aerospace Engineering, Astronomy and Astrophysics, Geophysics, Atmospheric Science, Space and Planetary Science, General Earth and Planetary Sciences
Electronic version(s): https://doi.org/10.1016/j.asr.2012.03.011 (Access: Closed)
: Details in the research portal "Research@Leibniz University"

BibTeX

@article{a8ad642ae04f43f8b6531adc1f17bb3e,
title = "Characteristics and accuracies of the GRACE inter-satellite pointing",
abstract = "For almost 10 years, the Gravity Recovery and Climate Experiment (GRACE) has provided information about the Earth gravity field with unprecedented accuracy. Efforts are ongoing to approach the GRACE baseline accuracy as there still remains an order of magnitude between the present error level of the gravity field solutions and the GRACE baseline. At the current level of accuracy, thorough investigation of sensor related effects is necessary as they are one of the potential contributors to the error budget. In the science mode operations, the twin satellites are kept precisely pointed with their KBR antennas towards each other. It is the task of the onboard attitude and orbit control system (AOCS) to keep the satellites in the required formation. We analyzed long time series of the inter-satellite pointing variations as they reflect the AOCS performance and characteristics. We present significant systematic effects in the inter-satellite pointing and discuss their possible sources. Prominent features are especially related to the magnetic torquer characteristics, star cameras' performance and KBR antenna calibration parameters. The relation between the magnetic torquer attitude control and the Earth magnetic field, impact of the different performance of the two star camera heads on the attitude control and the features due to uncertainties in the calibration parameters relating the star camera frame to K-frame are discussed in detail. Proper understanding of these effects will help to reduce their impact on the science data and subsequently increase the accuracy of the gravity field solutions. Moreover, understanding the complexity of the onboard system is essential not only for increasing the accuracy of the GRACE data but also for the development of the future gravity field satellite missions.",
keywords = "GRACE, Gravity field satellite mission, Inter-satellite pointing, Magnetic torquers, Sensor analysis, Star cameras",
author = "Tamara Bandikova and Jakob Flury and Ko, {Ung Dai}",
note = "Funding Information: This project is funded by the Centre for Quantum Engineering and Space-Time Research (QUEST) in Hannover . ",
year = "2012",
month = jul,
day = "1",
doi = "10.1016/j.asr.2012.03.011",
language = "English",
volume = "50",
pages = "123--135",
journal = "Advances in space research",
issn = "0273-1177",
publisher = "Elsevier Ltd.",
number = "1",
}