On Geolocation Uncertainty in Radio Occultation Observations for Ionospheric Scintillation Monitoring at Alaska

Radio occultation (RO) provides a cost-effective component of the overall sensor mix required to characterise the ionosphere over wide areas and in areas where it is not possible to deploy ground sensors. The paper provides a description of the RO constellation that has been developed and deployed by Spire Global. This constellation and its associated ground infrastructure is now producing data that can be used to characterise the bulk ionosphere, lower ionosphere perturbations and ionospheric scintillation.

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Ionospheric S4 Scintillations from GNSS Radio Occultation (RO) at Slant Path

Remote Sensing ◽

10.3390/rs12152373 ◽

2020 ◽

Vol 12 (15) ◽

pp. 2373

Author(s):

Dong L. Wu

Keyword(s):

Radio Occultation ◽

Satellite System ◽

Ionospheric Scintillation ◽

Equatorial Plasma Bubbles ◽

Low Latitudes ◽

Slant Path ◽

Sporadic E ◽

Dip Angle ◽

Navigation Signals ◽

Global Navigation Satellite

Ionospheric scintillation can significantly degrade the performance and the usability of space-based communication and navigation signals. Characterization and prediction of ionospheric scintillation can be made from the Global Navigation Satellite System (GNSS) radio occultation (RO) technique using the measurement from a deep slant path where the RO tangent height (ht) is far below the ionospheric sources. In this study, the L–band S4 from the RO measurements at ht = 30 km is used to infer the amplitude scintillation on the ground. The analysis of global RO data at ht = 30 km shows that sporadic–E (Es), equatorial plasma bubbles (EPBs), and equatorial spread–F (ESF) produce most of the significant S4 enhancements, although the polar S4 is generally weak. The enhanced S4 is a strong function of local time and magnetic dip angle. The Es–induced daytime S4 tends to have a negative correlation with the solar cycle at low latitudes but a positive correlation at high latitudes. The nighttime S4 is dominated by a strong semiannual variation at low latitudes.

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Supervised Detection of Ionospheric Scintillation in Low-Latitude Radio Occultation Measurements

Remote Sensing ◽

10.3390/rs13091690 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1690

Author(s):

Vinícius Ludwig-Barbosa ◽

Thomas Sievert ◽

Anders Carlström ◽

Mats Pettersson ◽

Viet Vu ◽

...

Keyword(s):

Radio Occultation ◽

Weather Prediction ◽

Geographical Location ◽

Solar Flux ◽

Gaussian Kernel ◽

Ionospheric Scintillation ◽

Support Vector ◽

Positive Contribution ◽

Data Set ◽

Svm Algorithm

Global Navigation Satellite System (GNSS) Radio Occultation (RO) has provided high-quality atmospheric data assimilated in Numerical Weather Prediction (NWP) models and climatology studies for more than 20 years. In the satellite–satellite GNSS-RO geometry, the measurements are susceptible to ionospheric scintillation depending on the solar and geomagnetic activity, seasons, geographical location and local time. This study investigates the application of the Support Vector Machine (SVM) algorithm in developing an automatic detection model of F-layer scintillation in GNSS-RO measurements using power spectral density (PSD). The model is intended for future analyses on the influence of space weather and solar activity on RO data products over long time periods. A novel data set of occultations is used to train the SVM algorithm. The data set is composed of events at low latitudes on 15–20 March 2015 (St. Patrick’s Day geomagnetic storm, high solar flux) and 14–19 May 2018 (quiet period, low solar flux). A few conditional criteria were first applied to a total of 5340 occultations to define a set of 858 scintillation candidates. Models were trained with scintillation indices and PSDs as training features and were either linear or Gaussian kernel. The investigations also show that besides the intensity PSD, the (excess) phase PSD has a positive contribution in increasing the detection of true positives.

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