17:15 〜 19:15
[PEM14-P19] Impact of plasma bubble on accuracy and integrity of air navigation around Ishigaki Island
キーワード：プラズマバブル、シンチレーション、航空航法
Equatorial plasma bubbles (EPBs) are observed as a depletion in the Total Electron Content (TEC) and are generated by plasma instabilities, such as the Rayleigh-Taylor instability. It is sometimes observed in low magnetic latitude regions. Irregularities in plasma density appear inside and edge of the EPBs and cause fluctuations in GNSS signals, known as amplitude scintillation. The amplitude scintillation is likely to cause the loss of lock signals and errors in pseudorange measurements, ultimately, the degrading positioning accuracy and integrity.
The Automatic Dependent Surveillance-Broadcast (ADS-B) is a surveillance technology primarily used by aircraft and airport vehicles. The ADS-B message includes a position derived from GNSS satellite positioning, barometric altitude, aircraft speed, and the aircraft's identity. It also broadcasts integrity and accuracy information known as the Navigation Integrity Category (NIC) and Navigation Accuracy Category for position (NACp). Typically, NIC and NACp values are greater than 7 and 8, respectively, indicating that the radius of containment around the aircraft (Rc) is less than 185.2 meters and the Estimated Position Uncertainty (EPU) is less than 30 meters.
A degradation of NIC and NACp sometimes observed in the low latitudes. This suggests that the accuracy and integrity of GNSS positioning are degraded by EPBs. It is necessary to investigate the impact of EPBs on satellite navigation of aircraft. This study aims to evaluate the impact of EPBs on the accuracy and integrity of GNSS positioning in aircraft based on data observed from a scintillation receiver, all-sky camera, and ADS-B receiver installed in low latitudes.
Since 2020, the Electronic Navigation Research Institute (ENRI) has been recording ADS-B messages at Ishigaki Island. At Ishigaki, an All-sky airglow imager (ASI) and a GNSS receiver have been installed. The ASI enables the detection of EPBs, which appear as regions of plasma density depletion, causing amplitude scintillation. The GNSS receiver used is the Septentrio PolaRx5S, which provides phase and amplitude scintillation indices with a 1-minute sampling rate. Therefore, the degradation of NIC and NACp due to ionospheric activity can be investigated on Ishigaki.
On March 16, 2024, EPBs were observed in the airglow image, and increases in the S4 index for southern satellites were detected by the scintillation receiver. At that time, the degradation of NIC and NACp broadcasted from JJA2612 was observed. We compared the location of the EPBs with the ionospheric pierce point (IPP) of GPS satellites for JJA2612. The IPPs of G25 for JJA2612 is located at the edge of the plasma bubble, suggesting that JJA2612's NIC and NACp degradation may be caused by the plasma bubble. However, aircraft, which flew close to the JJA2612, did not show degradation in NIC and NACp. Thus, ionospheric disturbances such as plasma bubbles are unlikely to significantly impact aircraft operations. The observed degradations are more likely attributable to radio interference, spoofing, or equipment failure.
In this presentation, we will show cases of NIC and NACp degradation during periods of high geomagnetic activity, particularly on March 16, 2024, described above, and other events observed from May 2023 to December 2024. Finally, we discuss the contribution of geomagnetic activity to the degradation of NIC and NACp.
The Automatic Dependent Surveillance-Broadcast (ADS-B) is a surveillance technology primarily used by aircraft and airport vehicles. The ADS-B message includes a position derived from GNSS satellite positioning, barometric altitude, aircraft speed, and the aircraft's identity. It also broadcasts integrity and accuracy information known as the Navigation Integrity Category (NIC) and Navigation Accuracy Category for position (NACp). Typically, NIC and NACp values are greater than 7 and 8, respectively, indicating that the radius of containment around the aircraft (Rc) is less than 185.2 meters and the Estimated Position Uncertainty (EPU) is less than 30 meters.
A degradation of NIC and NACp sometimes observed in the low latitudes. This suggests that the accuracy and integrity of GNSS positioning are degraded by EPBs. It is necessary to investigate the impact of EPBs on satellite navigation of aircraft. This study aims to evaluate the impact of EPBs on the accuracy and integrity of GNSS positioning in aircraft based on data observed from a scintillation receiver, all-sky camera, and ADS-B receiver installed in low latitudes.
Since 2020, the Electronic Navigation Research Institute (ENRI) has been recording ADS-B messages at Ishigaki Island. At Ishigaki, an All-sky airglow imager (ASI) and a GNSS receiver have been installed. The ASI enables the detection of EPBs, which appear as regions of plasma density depletion, causing amplitude scintillation. The GNSS receiver used is the Septentrio PolaRx5S, which provides phase and amplitude scintillation indices with a 1-minute sampling rate. Therefore, the degradation of NIC and NACp due to ionospheric activity can be investigated on Ishigaki.
On March 16, 2024, EPBs were observed in the airglow image, and increases in the S4 index for southern satellites were detected by the scintillation receiver. At that time, the degradation of NIC and NACp broadcasted from JJA2612 was observed. We compared the location of the EPBs with the ionospheric pierce point (IPP) of GPS satellites for JJA2612. The IPPs of G25 for JJA2612 is located at the edge of the plasma bubble, suggesting that JJA2612's NIC and NACp degradation may be caused by the plasma bubble. However, aircraft, which flew close to the JJA2612, did not show degradation in NIC and NACp. Thus, ionospheric disturbances such as plasma bubbles are unlikely to significantly impact aircraft operations. The observed degradations are more likely attributable to radio interference, spoofing, or equipment failure.
In this presentation, we will show cases of NIC and NACp degradation during periods of high geomagnetic activity, particularly on March 16, 2024, described above, and other events observed from May 2023 to December 2024. Finally, we discuss the contribution of geomagnetic activity to the degradation of NIC and NACp.