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Ann. Geophys., 25, 87-97, 2007
www.ann-geophys.net/25/87/2007/
© European Geosciences Union 2007
Modelling and observation of transionospheric propagation results from ISIS II in preparation for ePOP
R. G. Gillies1, G. C. Hussey1, H. G. James2, G. J. Sofko1, and D. André1
1Institute for Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
2Communications Research Centre, Ottawa, Ontario, Canada
Abstract. The enhanced Polar Outflow Probe (ePOP) is scheduled to be launched as part
of the Cascade Demonstrator Small-Sat and Ionospheric Polar Explorer
(CASSIOPE) satellite in early 2008. A Radio Receiver Instrument (RRI) on ePOP
will receive HF transmissions from various ground-based transmitters. In
preparation for the ePOP mission, data from a similar transionospheric
experiment performed by the International Satellites for Ionospheric Studies
(ISIS) II satellite has been studied. Prominent features in the received
9.303-MHz signal were periodic Faraday fading of signal intensity at rates up
to 13 Hz and a time of arrival delay between the O- and X-modes of up to
0.8 ms. Both features occurred when the satellite was above or south of the
Ottawa transmitter. Ionospheric models for ray tracing were constructed using
both International Reference Ionosphere (IRI) profiles and local peak
electron density values from ISIS ionograms. Values for fade rate and
differential mode delay were computed and compared to the values observed in
the ISIS II data. The computed values showed very good agreement to the
observed values of both received signal parameters when the topside sounding
foF2 values were used to scale IRI profiles, but not when strictly modelled
IRI profiles were used. It was determined that the primary modifier of the
received signal parameters was the foF2 density and not the shape of the
profile. This dependence was due to refraction, at the 9.303-MHz signal
frequency, causing the rays to travel larger distances near the peak density
where essentially all the mode splitting occurred. This study should assist
in interpretation of ePOP RRI data when they are available.
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