Transionospheric signal modelling for epop and Superdarn

Abstract

In 2011, the Canadian enhanced Polar Outflow Probe (ePOP) satellite will be launched. The ePOP satellite is equipped with several scientific Earth observation instruments, including a Radio Receiver Instrument (RRI) which will be used to detect High Frequency (HF) radio waves transmitted from a ground-based transmitter. The ground-based instrument will be one of the Super Dual Auroral Radar Network (SuperDARN) array of radars. A radio wave transmitted from the SuperDARN radar will propagate through the ionosphere and be detected by the RRI on ePOP. Analysis of the characteristics of the signal received by the RRI will provide information about the plasma density in the ionosphere between the transmitter and receiver. As the ePOP satellite is not yet operational, extensive ray path modelling has been performed to simulate the expected signal at the RRI for various ionospheric conditions.

The other major objective of this research was to examine the effect of the variable refractive index in the ionosphere on SuperDARN drift velocity measurements. Past comparisons between velocities measured by SuperDARN and other instruments have found that velocities measured by SuperDARN typically were about 20-30% lower. This research has shown that underestimation of drift velocities by SuperDARN is a consequence of not including the refractive index when these velocities are calculated. As refractive index measurements are not readily available, this research has involved developing and implementing various methods to estimate the refractive index in the ionosphere. These methods have demonstrated that plasma density values within the SuperDARN scattering volume are appreciably higher than background plasma densities in the ionosphere. Application of these methods, which has resulted in a much better understanding of the physics of the coherent scattering process, has resulted in agreement between velocities measured by SuperDARN and other instruments.