Automated Scaling Software for Oblique Incidence Ionograms

ABSTRACT: The objective of this solicitation is to develop real-time automatic scaling software for oblique ionograms (OIs).In Phase I, using recently developed mathematical concepts of sparsity and fractional norms, we have developed a novel method for detecting the desired trace data and determining whether a given point is an ordinary magnetoionic mode (O) or an extraordinary mode (X) while reducing selection of noise/interference data.A selected OI trace could be converted to an approximately equivalent vertical ionogram using the laws of virtual geometry (VG) and inverted to an electron density profile, but this is an unnecessarily inaccurate method.We have instead assimilated the OI trace data directly into NWRAs assimilative ionosphere model, GPSII (GPS Ionospheric Inversion).This approach allows for ionospheric horizontal gradients that would be lost in the VG approach.In Phase II we will further develop this new method of automatically scaling oblique ionograms into a robust system suitable for use in routine operations.This will require making the trace extraction algorithm more robust to disturbed ionograms and significantly reducing processing times.We will exercise the new code on a wide variety of real measured ionograms and perform performance analyses.; BENEFIT: An automated system for finding oblique ionogram trace points will allow for real time assimilation of potentially dense networks of ionosondes.The Australian DSTO has already fielded such a network, the Dense Integrated Network of Ionospheric Sensors (DINIS), for defining the propagation environment of their OTH radar system, JORN.A similar networked sounding system has been proposed for the US Next Generation OTH Radar (NGOTHR).Making best use of the ionograms provided by an ionospheric sounding network to improve the geolocation accuracy of NGOTHR will require a direct 3D ionospheric data assimilation algorithm like NWRAs GPS Ionospheric Inversion (GPSII).For GPSII to function without a human in the loop, as will be necessary for the throughput required of NGOTHR, automated trace extraction will be required.This capability will also benefit the intelligence community.A limitation of HF geolocation of emitters in denied territories is the inability to measure the ionosphere in the denied region using vertical ionosondes.However, it is often completely reasonable to propagate over a denied region using oblique-incidence HF paths, that is, oblique ionograms.GPSII is already being evaluated in the IARPA HFGeo program and has proven to provide unparalleled accuracy in accounting for the signal deflections caused by medium-scale traveling ionospheric disturbances (TIDs).A reliable OI autoscaling capability will extend the benefit of GPSII to HFGeo in denied territories.