11:00 AM - 1:00 PM
[PEM10-P15] Detection of ionospheric disturbance associated with Hayabusa2's Capsule re-entry using GNSS-TEC Spatio-temporal Tomography
Keywords:GNSS-TEC, tomography, ionosphere
December 6, 2020, the Hayabusa2 capsule successfully re-entered the Earth with a sample from the asteroid RYUGU. The capsule penetrated the ionosphere and atmosphere with about 12 km/s. It generated a shock wave due to the interaction with the atmosphere. As a result, it propagates the ground and also the ionosphere. Total Electronic Contents (TEC) analysis based on GNSS observations can detect the energy propagation of the shock waves through the ionosphere. In general, even in the case of flying objects such as rockets and missiles that penetrate the ionosphere, their trajectories can be followed by GNSS-TEC analysis. However, it is known that although shock waves are generated, water vapor is generated due to the combustion of chemical propulsion fuel, and the water vapor combines with electrons in the ionosphere, depleting the electrons in the ionosphere. Therefore, it is difficult to estimate the mechanical response of the ionosphere from a normal artificial flying object because GNSS-TEC analysis observed the depletion of electrons due to chemical reactions. Against this background, GNSS-TEC observations have become increasingly important in recent studies, such as a response from seismic and tsunami waves and eruptions.
The clarification of the mechanical response is necessary for more quantitative discussions.
We attempted to capture the ionospheric disturbance caused by the re-entry of the Hayabusa2 capsule into the Earth by conducting high-sampling campaign GNSS observations on the ground and TEC analysis. For this purpose, we constructed a high-sampling GNSS observation network near Woomera, Australia, where the capsule is scheduled to arrive, and observed the ionospheric disturbances caused by the capsule's re-entry into the Earth. These GNSS data include apparent TEC changes due to the movement of the GNSS satellites. Since it is necessary to take them into account, we constructed a Spatio-temporal TEC tomography method of the ionosphere by TEC and applied it to this observation.
To Spatio-temporal GNSS-TEC tomography, this study divided the area over Woomera, Australia, into seven layers from 120 to 420 km hight, about 50 x 50 blocks (30 km to 50 km). To the stability of the solution, we introduce smoothing constrain into the spatially adjacent blocks as a priori information and controlled by a damping parameter. Since the observed GNSS-TEC data is continuous in the time direction, the obtained time variation is also continuous. Therefore, we do not introduce any a priori smoothing in the time direction and estimated the TEC variation independently for each time step. The analysis time is about 10 minutes before and after the closest approach time of Hayabusa2.
We use 288 GNSS stations mainly in Australia for GNSS-TEC tomography. The GNSS-TEC data obtained from the combination of GNSS stations and satellites was about 120,000 traces. Among this data, we extracted the combinations that passed through each block at each time step and used them as analysis data. The number of data differs for each time step, but we used about 700 to 1200 TEC data for each time step.
We develop a Spatio-temporal TEC model with more than 90% noise reduction. On the other hand, the noise reduction varies from 70% to 95% depending on the value of damping parameters, and it is necessary to study the choice of optimized damping parameters. As a result of the analysis, we can show the Spatio-temporal variation of ionospheric disturbance due to re-entry of Hayabusa2's Capsule.
The figure shows a result of Spatio-temporal GNSS-TEC tomography. The green square is Hayabusa2.
The clarification of the mechanical response is necessary for more quantitative discussions.
We attempted to capture the ionospheric disturbance caused by the re-entry of the Hayabusa2 capsule into the Earth by conducting high-sampling campaign GNSS observations on the ground and TEC analysis. For this purpose, we constructed a high-sampling GNSS observation network near Woomera, Australia, where the capsule is scheduled to arrive, and observed the ionospheric disturbances caused by the capsule's re-entry into the Earth. These GNSS data include apparent TEC changes due to the movement of the GNSS satellites. Since it is necessary to take them into account, we constructed a Spatio-temporal TEC tomography method of the ionosphere by TEC and applied it to this observation.
To Spatio-temporal GNSS-TEC tomography, this study divided the area over Woomera, Australia, into seven layers from 120 to 420 km hight, about 50 x 50 blocks (30 km to 50 km). To the stability of the solution, we introduce smoothing constrain into the spatially adjacent blocks as a priori information and controlled by a damping parameter. Since the observed GNSS-TEC data is continuous in the time direction, the obtained time variation is also continuous. Therefore, we do not introduce any a priori smoothing in the time direction and estimated the TEC variation independently for each time step. The analysis time is about 10 minutes before and after the closest approach time of Hayabusa2.
We use 288 GNSS stations mainly in Australia for GNSS-TEC tomography. The GNSS-TEC data obtained from the combination of GNSS stations and satellites was about 120,000 traces. Among this data, we extracted the combinations that passed through each block at each time step and used them as analysis data. The number of data differs for each time step, but we used about 700 to 1200 TEC data for each time step.
We develop a Spatio-temporal TEC model with more than 90% noise reduction. On the other hand, the noise reduction varies from 70% to 95% depending on the value of damping parameters, and it is necessary to study the choice of optimized damping parameters. As a result of the analysis, we can show the Spatio-temporal variation of ionospheric disturbance due to re-entry of Hayabusa2's Capsule.
The figure shows a result of Spatio-temporal GNSS-TEC tomography. The green square is Hayabusa2.