Data analysis of GOCE sensors in different frequency bands
19/09/2016 | 16:45 | Session 1: Current and future satellite gravity missions
Author(s): Elisabeth Reußner, Anja Schlicht and Peter Schack
Elisabeth Reußner, Anja Schlicht and Peter Schack
The main result of the GOCE mission was the availability of a static gravity field with high spatial resolution and accuracy. The main instrument on board to reach this goal was the electrostatic gravity gradiometer (EGG), which has three axes being orthogonal to each other and accelerometers at both ends of these axes. From each of these pairs of accelerometers the common mode (CM) and the differential mode (DM) of one pair can be calculated. The CM is the mean value of the two measurements from the accelerometers and is used for the control of the ion thruster. The DM is the semi difference of the measurements from an accelerometer pair and contains the gravity gradient beside the angular rates and the angular accelerations. As the measurements of the EGG have a limited bandwidth due to bias drift, additional information from other instruments is necessary for the calculation of the angular rates. The angular rate reconstruction (ARR) is a method optimized by C. Stummer, which combines data from the EGG and the star trackers in order to obtain optimal angular rates. Beside the information from these two instruments the GOCE mission has provided a lot of data from further sensors on board, which registered several signals with different frequencies.
The Vyy component of the gradient tensor shows structures at the poles and the equator, which indicate that further investigations on the provided data is necessary. Therefore, in the beginning it is required to understand and analyse the sensors’ output. Finally, it should be excluded that the measurements used for the calculation of the gravity field model do not contain any contributions, which are due to not considered instrument errors and therefore lead to false interpretations of the results.
For this purpose it is initially necessary to get an overview over the various sensor performances in different frequency bands. Previous studies focused on the representation of the derived data in the frequency domain. In the context of the current investigations the filtered data is represented in the time domain and the spatial domain.
The poster focuses on the angular accelerations delivered by the EGG and by the star trackers as well as on information of the ion thruster and magnetometer. The investigations deliver a first step in the error analysis of the GOCE sensors using Level 1b and Level 2 data of the mission with the goal to receive information for possible corrections of existing gravity field models from GOCE. Beyond this, insight into the interaction of a low earth orbiting satellite with its surrounding ionosphere and thermosphere might be obtained.