The Initial Results from the LITN of the FORMOSAT-3 TBB Program

Abstract

AB STRACTBe gin ning in 2006, four ground sta tions lo cated at Chung-Li (25.136°N, 121.539°E), TasoTun (23.981°N, 120.697°E), CheCheng (22.725°N, 120.544°E), and trop i cal Itu Aba Is land (10.06°N, 114.350°E) were set up to re ceive bea con sig nals from six FORMOSAT-3/COS MIC (Bernhardt et al. 2000) and other NNSS-like sat el lites. By ap ply ing dif fer en tial Dopp ler tech nique on three quad ra ture com po nents of the three-band bea con sig nals, we were able to ob tain to tal elec tric con tents (TEC) val ues and scin til la tion along the ra dio path through the ion o sphere. Such mea sure ments can be used to de rive re gional ion o spheric ir reg u lar ity and to mog ra phy. In this pa per, we have con firmed the power pat terns con trib uted from the trans mit ting an ten nas on board FS3/COS MIC and the ground-based re ceiv ing an ten nas. The multi pli ca tive al ge braic re con struc tion tech nique (MART) al go rithm has also been im ple mented to re con struct ion o spheric to mog ra phy im ages. Ob ser va tions of the di ur nal vari a tions and the dy nam ics of equa to rial anom aly showed that the equa to rial anom aly ap peared at 0800 LT, and then sub se quently moved to ward the Earth's poles. The north crest was stron gest at ~1300 LT and its core was lo cated at about 10°N of the mag netic lat i tude (~20°N geo graphic latitude). Afterwards, the crest moved toward the equator after sunset and disappeared after midnight.Key words: To tal elec tron con tent (TEC), Equatorial anomaly, Ion o spheric to mog ra phy, Bea con re ceiver Ocean. Sci., 20, 261-271, doi: 10.3319/TAO.2007.12.03.01(F3C) IN TRO DUC TIONThe elec tron den sity dis tri bu tion in the ion o sphere exhib its a com pli cated struc ture and dy namic be hav ior that has been stud ied for many years. The ion o sphere af fects the re liabil ity of sat el lite com mu ni ca tions and the ac cu racy of ra dio as tron omy. There are sev eral tech niques in mea sur ing the ion o spheric elec tron den sity from ground sta tions. The ionosonde, which is es sen tially a one-di men sional ra dar measures the max i mum elec tron den sity in an up wardly di rection. On the other hand, the in co her ent scat ter ra dar can measure ion o spheric elec tron den sity in a three di mensional man ner. How ever, as there are only eight or nine such ra dars in the world, lim ited cov er age is achieved. Ion ospheric to mog ra phy is an other tech nique that can be used to ob tain in for ma tion about the ion o spheric elec tron den sity. An ion o spheric to mog ra phy sys tem con sists of a nav i ga tional sat el lite usu ally or bit ing at a LEO al ti tude be tween 800 to 1200 km, along with sev eral ground sta tions po si tioned in a line di rectly un der the LEO sat el lite's or bital path. A typ ical con fig u ra tion for an ion o spheric to mog ra phy sys tem is shown in Fig. 1. The data mea sured at the ground sta tions are to tal elec tron con tent (TEC) val ues. The TEC data can be ex pressed as Eq. (1): (1) where the N e is the elec ...

Retrospect and prospect of ionospheric weather observed by FORMOSAT-3/COSMIC and FORMOSAT-7/COSMIC-2

“…Based on the time delay and the bending angle of GPS signals recorded by the radio occultation (RO) technique, the electron density profiles in the ionosphere as well as temperature, pressure, and water content profiles in the atmosphere can be derived (Anthes et al 2008). There are also two other payloads carried by each F3/C satellite including, a tiny ionospheric photometer (TIP) to observe the nighttime ionospheric airglow emission of 135.6 nm emissions around the F2-peak height (Chua et al 2009;Coker et al 2009;Dymond et al 2009), and a tri-band beacon (TBB) to tomographically estimate fine structures of ionospheric electron density and scintillations of the signals on the satellite-to-receiver plane (Hsiao et al 2009).…”

Preliminary observation results of the Coherent Beacon System onboard the China Seismo-Electromagnetic Satellite-1

“…where y i is the i th absolute slant TEC (STEC) in a column of m measurements, is the j th resulted cell electron density at the k th iteration with 0< λ k <1 (Hsiao et al, ), h ij is the length of link i that lies in cell j . NeQuick model is served as an initial guess for the MART algorithm.…”

“…The MART algorithm used in the software is implemented as the following equation (2): VHF≥1.5 dBW UHF≥1.5 dBW L≥4.0 dBW * "I" is the in-phase component of the waveform, and "Q" represents the quadrature component. where is the ith absolute slant TEC (STEC) in a column of m measurements, is the jth resulted cell electron density at the kth iteration with 0< <1 (Hsiao et al, 2009), is the length of link i that lies in cell j. NeQuick model is served as an initial guess for the MART algorithm.…”

“…The most commonly used algorithms based upon pixels include: the algebraic reconstruction technique (ART), the simultaneous iterative reconstruction technique (SIRT), and the multiplicative algebraic reconstruction technique (MART). MART has an advantage over ART (SIRT is an improved version of ART) in determining the electron densities, because it avoids unreasonable negative values (Hsiao et al, ). Thus, the MART inversion method has been selected, for now, as the CBS's default CIT algorithm.…”