"Attitude is a little thing that makes a big difference." Sir Winston Churchill
The precise attitude determination and control (ADC) is one of the key tasks for almost every satellite mission. Attitude determination is a process of estimating the attitude based on sensor measurement. Attitude control is then a process of maintaining or changing the attitude using either natural forces or actuators. The attitude is to be distinguished from the position. The position of a spacecraft informs us about where the satellite’s center of mass is located in space, whereas the attitude describes the motion about this center of mass.
The ADC secures the fundamental requirements for mission operation. Such requirements may be for example orientation of the solar arrays towards the Sun, orientation of the receiver and transmitter antennas towards the Earth or, as in case of GRACE and GRACE Follow-On, the maintenance of the inter-satellite pointing. The precise inter-satellite pointing allows the inter-satellite ranging, which is one of the key techniques for the global gravity field observation along with the precise orbit determination and the precise accelerometry. The precise information about the satellite’s attitude is not only crucial for the satellite in-orbit operation, but also for the post-processing of the scientific observations needed for the gravity field recovery, e.g. of the inter-satellite ranging observations, GNSS observations and the accelerometer data. Highest possible accuracy of the attitude data is absolutely essential as any inaccuracies or untreated systematic errors in the attitude data will directly propagate into the gravity field models. Therefore several studies of the GRACE attitude data have been undertaken in order to improve their current accuracy. In frame of the EGSIEM project, the GRACE attitude data analysis is further carried out. Some of the recent studies carried out by the EGSIEM members are listed below:
Bandikova T., Flury, J. (2014): Improvement of the GRACE star camera data based on the revision of the combination method, Advances in Space Research, 54 (9):1818–1827 DOI: 10.1016/j.asr.2014.07.004
Bandikova T, Flury J (2015): Attitude determination and its impact on the current and the future inter-satellite ranging missions, 26th IUGG General Assembly, Prague, Czech Republic, 26.6.2015
Klinger B, Mayer-Gürr T (2015): Improved GRACE preprocessing methodologies: Impact on monthly gravity field solutions, 26th IUGG General Assembly, Prague, Czech Republic, 24.6.2015
