All Terrastar Users: High Levels of Ionospheric activity

Ionospheric activity is forecast to build to possible G3 (strong) levels from approximately 21:00 to 23:59 UTC on the 11th of May 2023. The Ionosphere is expected to remain active for several hours before decreasing. Area of impact is primarily poleward of 65 degrees Geomagnetic Latitude.

 Increased ionospheric activity is correlated with the following factors:

• Solar and Magnetic storms – cause an increase in the ionospheric activity;
• Sunspot Activity – increased ionospheric activity linked with the 11 year solar cycle.
• Geographic Location – highest activity along geomagnetic equator and in auroral (polar) regions;
• Seasonal Variations – increased activity at the Vernal and Autumnal Equinoxes;
• Diurnal (Daily) Variations – maximum effects normally experienced one hour after local sunset until midnight.   

The most significant effect for Precise Point Positioning (PPP) services is scintillation which is caused by small scale irregularities in the ionosphere caused by the solar activity. Scintillation occurs mainly in the evening along the geomagnetic equator. It has the effect of causing fluctuations in the amplitude and phase of the carrier phase signal introducing noise or causing loss of lock to the satellite. This results in a reduced number of usable GNSS satellites and occasionally a reduction in the L-Band communications link strength causing intermittent reception of the augmentation data.

Scintillation affects are normally seen in a period of 6 hours after sundown and are not predictable.

Although there is no way to eliminate the effects of scintillation, TERRASTAR recommend the following to help mitigate the impact of scintillation:

• Use of as many GNSS constellations as possible to increase the number of observations available to the position solution.  TerraStar correction services include support for GPS, GLONASS, Galileo and BeiDou.
• Use of all available L-band beams to ensure that corrections can still be received if lock to one satellite is lost.  Users can also access corrections over an IP feed.  With OEM6, users can choose to auto-assign beams to avoid reliance on a single manually selected beam.  All OEM7 receivers simultaneously track all available L-band, so a user should be unaffected by a loss of data from any single beam.