Ionopsheric sensing of the International Space Station via GNSS total electron content

As the number of spacecraft in orbit has increased over the last half century so has the amount of space debris. Small space debris on the order of millimeters poses an existential threat to spacecraft in orbit as they can cause holes in structures and disable critical electronic systems. Current ground based radar and optical methods are unable to map such small debris. We are investigating a new method of detection that entails characterizing the plasma wake that is produced as a piece of debris travels through the upper ionosphere.An experiment was conducted using GNSS (global navigation satellite system) based ionosphere sensing to detect the plasma wake in the vicinity of a known large object, the International Space Station (ISS). It is expected that when a spacecraft crosses the radio line-of-sight from a GNSS satellite to a ground station, there will be a detectable effect on the total electron content (TEC) from that link. Orbital ephemeris data was processed to find occultations between the ISS and GPS satellites over ground stations in the Canadian High Arctic Ionospheric Network (CHAIN). For each occultation, historical GNSS signal data from the CHAIN database was used to analyze phase and amplitude scintillations during the time range of the occultations. Simultaneous phase and amplitude scintillations of 5 seconds or more and of greater magnitude than the background signal scintillation were indicative of possible debris wake. Any kind of space weather event can cause electron density fluctuations which can be observed by the GNSS network. Similarly, a piece of debris passing through the upper ionosphere can cause a total electron density (TEC) decrease in a local area. Large decreases in TEC further indicated a potential debris event. However, space weather such as geomagnetic storms or solar flare activity can also cause the observed phenomena in the GNSS TEC and scintillation data. It is important to rule out these natural causes by examining the Kp and F10.7 indices to determine if there was any significant solar or geomagnetic activity that could impact the TEC. Lastly, some kind of pattern recognition will need to be implemented to correlate all the GNSS data and confirm a debris event.