Ionospheric Tomography from a Reference GPS/MET Experiment Through the IRI Model

Abstract

In earlier studies, we implemented the Multiplicative Algebraic Reconstruction Technique (MART) to reconstruct two-dimensional ionospheric structures from measured TECs through the receptions of the GPSto-LEO signals and/or the NNSS-to-ground beacon signals. To examine the accuracy of the reconstructed image we need ground-based validation systems which are difficult to obtain. However, such comparative investigation is needed if one aims to improve tomography inverse techniques and algorithms. In this study, we propose a simulation scheme to carry out this task. We first simulate the GPS-to-LEO TEC measurements through the IRI model by integrating electron densities along the "straight" ray occultation paths between the GPS and LEO satellite obtained from the real GPS/MET experiment. Contiguous tomographic images are then derived by the MART algorithm within the "reference" GPS/MET experiment. They are verified by comparison with the "true" IRI-modelled ionosphere. We show that simulation/reference results can be used to find the optimal reconstruction strategy in space-based ionospheric tomography.

COSMIC/FORMOSAT‐3 tomography of SEP ionization in the polar cap

“…A 3‐D EC distribution can thus be deduced through relaxation using red‐black smoothing on numerous EC height profiles. This 3‐D EC image is used as an initial guess to start the iterative Multiplicative Algebraic Reconstruction Technique (MART) algorithm, and 3‐D tomography of the EC is then produced around whole globe with a time step of 2 hours and spatial grid of 5° in longitude, 1° in latitude, and 5 km in height [ Tsai et al , 2006]. Such tomographic investigations would give valuable information in a wide region and without use of models.…”

FORMOSAT-3/COSMIC science mission update

“…The deployment of the Pacific chain is planned as three strips, consisting of six to ten stations along the FORMOSAT-3 orbit trajectories. Tsai et al (2002bTsai et al ( , 2003 studied the integration of the ionospheric RO data into CIT.…”

Ionospheric Electron Density Concurrently Derived by TIP and GOX of FORMOSAT-3/COSMIC

“…As the as sump tion of spher i cal sym me try used in the Abel in te gral trans form is not re al is tic in gen eral, we adopt the im proved ap proach of Tsai et al (2006Tsai et al ( , 2009) con sid ering and de riv ing hor i zon tal gra di ents of the elec tron den sity by close-up occultation pro files re trieved from the stan dard Abel in ver sion. That is the den sity dis tri bu tion is used to com pen sate the TEC from Abel in ver sion us ing the dif ference be tween the tan gent point elec tron den sity and the real elec tron den si ties along the occultation rays.…”

“…Tsai et al (2002) implemented the Multi pli ca tive Al ge braic Re con struc tion Tech nique (MART) to re con struct the ion o sphere pro jected onto the LEO-or bital plane us ing mea sured TECs through the re cep tions of the GPS-to-LEO sig nals. The re con structed elec tron den sity by the LEO to mog ra phy with the com pen sated TEC yields better re sults than the orig i nal verti cal pro files re trieved from the GPS occultation data by the Abel trans for ma tion, be ing in a better agree ment in both peak elec tron den sity NmF 2 and height hmF 2 to nearby ionosonde mea sure ments (Tsai et al 2006). The TIP mea sures hor i zon tal struc ture of the ion o sphere with high pre ci sion and high spa tial res o lu tion Coker et al 2009;Dymond et al 2009).…”

“…We fur ther de rive and iso late the con cur rent data of LEOcom pen sated to mog ra phy by us ing Tsai et al (2006), and com bine the two re sults to yield LEO-TIP tomographic inver sions (Fig. 1).…”