The Cyprus ionosonde has been operating for almost ten years since 2009, monitoring ionospheric conditions over the eastern Mediterranean region. It is the only ionosonde operating in the area and it does not contribute to any existing European database and subsequently has not been utilised in the frames of any Space Situational Awareness (SSA) program. Therefore a quantitative assessment of the benefit of introducing the Cyprus ionosonde in the European Ionosonde Service (EIS) which facilitates nowcasting and forecasting of ionospheric conditions over Europe in the frames of ESA SSA services will indicate whether a significant improvement of EIS over the eastern Mediterranean is possible and will pave the way for extending EIS coverage over the region. Such a preparatory investigation is related to a recent ESA Intended Invitation To Tender with a title “Space Weather user needs for the Mediterranean region”.      

Another SSA technology development currently considered with a high priority is 3D Ionospheric Modelling (STA-SWE-134). Regarding electron density profile measurements (EDP) Incoherent Scatter Radars (ISR) cover the part of the profile up to 700 km but their number is limited and ionosondes can only provide bottomside measurements.  In the absence of any topside sounders (such as past missions Intercosmos and Isis) currently the only reliable available direct topside electron density measurements with extended spatial coverage is provided in situ by Langmuir probe (SWARM mission, past CHAMP mission) or indirect comparisons using TEC measurements which are not sufficiently adequate to incorporate topside profile shape information into assimilation procedures. Atmospheric probing by GNSS radio occultation (RO) measurements on board Low Earth Orbiting (LEO) satellites is a powerful technique for monitoring the vertical structure of the ionosphere (including the topside up to the LEO altitude) and therefore to collect information on key ionospheric characteristics covering areas of the globe such as oceans where ground instrumentation such as GNSS receivers and radars are impossible to operate. However for space weather operations, there are still quality control issues that need to be addressed before the exploitation of these measurements becomes possible for operational applications. There is therefore a need to determine whether it is possible to assimilate RO EDPs in 3D ionospheric modelling activities over Europe in the near future and specify the conditions under which this is feasible. This is very important in anticipation of the extended RO dataset of the F7/C2 mission in the coming years.

The first technical objective of the project is to assess whether an introduction of the Cyprus ionosonde into the existing EIS SSA service will improve the ionospheric representation over the eastern Mediterranean region and to what extent. In practice this assessment will be based on quantifying the degree of mis-representation in MHz of foF2 over Nicosia (based on auto and manually scaled foF2 values from Cyprus ionosonde) by EIS nowcasting maps during the period 2009-2018 encapsulating almost a full solar cycle of foF2 data at 15 min resolution. In this respect by quantifying the discrepancy in foF2 values (ΔfoF2) extracted from EIS nowcasting maps with auto and manually scaled foF2 values measured over Nicosia we will be in the position to quantify on various time scales the level of EIS improvement (based on this ΔfoF2) that is expected to be achieved over the eastern Mediterranean region if the Cyprus ionosonde is incorporated in SSA EIS in the future.

The second technical objective is to is to assemble a RO EDP dataset over Europe (2006-2018) based on past (CHAMP,GRACE) and present (FORMOSAT3/COSMIC-F3/C) RO missions and use the EIS nowcasting foF2 maps over Europe as a benchmark (by exploiting the coverage provided by the 10 ionosondes contributing to EIS) to evaluate  the latitude and longitude effect (at a high spatial resolution) in the discrepancy of RO derived foF2 with interpolated values from the EIS. This will indicate the expected degree to which one important criterion (accurate RO foF2 values is satisfied quantifying the anticipated percentage from available RO EDPs in future RO missions to exploit their topside RO EDPs in ionospheric assimilation procedures over Europe).

The third technical objective is to assemble a unique dataset of RO EDPs which will be validated against collocated (in space and time) European ionosonde EDPs through manual scaling of the corresponding ionograms from Global Ionospheric Radio Observatory (GIRO).  This will indicate the extent to which both important criteria are satisfied indicating the percentage of RO EDP available to exploit their topside RO EDP in assimilation procedures over Europe. This will also give the opportunity to conduct an investigation on the local or regional ionospheric conditions and occultation parameters that could give rise to significant discrepancies between ionosonde and RO EDPs facilitating a comprehensive definition of the conditions that would enable assimilation of topside profiles in 3D ionospheric representation procedures over Europe in the future.

Researchers

Haris Haralambous / Frederick University

Christina Oikonomou / Frederick University

Theodoros Leontiou / Frederick University

Michalis Makrominas / Frederick University