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

Abstract

AB STRACTThe tiny ion o spheric pho tom e ter (TIP) and GPS occultation ex per i ment (GOX) onboard FORMOSAT-3/COS MIC (F3/C) are em ployed to mea sure the OI 135.6 nm in ten si ties in the na dir di rec tion and the to tal elec tron con tent (TEC) be tween the F3/C and GPS sat el lite in the ion o sphere, re spec tively. Due to its very high sen si tiv ity ~600 counts/Ray leigh and rather nar row na dir point ing 3.8° cir cu lar field-of-view, the TIP pro vides ac cu rate char ac ter iza tion of ion o spheric elec tron den sity gra di ents in the hor i zon tal di rec tion. Mean while, a tech nique of the low earth or bit (LEO) to mog ra phy is ap plied to an a lyze the GOX data ob tain ing the 3D dis tri bu tion of ion o sphere elec tron den sity. Here, we com bine the two ob ser va tions to carry out the LEO-TIP tomographic in ver sions, and dem on strate that the peak elec tron den sity (NmF 2 ) re trieved from the TIP com bined to gether with the peak al ti tude (hmF 2 ) in for ma tion from the LEO tomography profiles provides more realistic electron density.Key words: Tiny ion o spheric pho tom e ter (TIP), GPS occultation ex per i ment (GOX), FORMOSAT-3/COS MIC (F3/C), LEO to mog ra phy, LEO-TIP tomographic in ver sion, Ion o spheric elec tron density Tsai, H. F. Tsai, C. H. Lin, K. F. Dymond, C. Coker, D. H. Chua, S. A. Budzien, and C. Z. Cheng, 2009: Ion o spheric elec tron den sity con cur rently de rived by TIP and GOX of FORMOSAT-3/COS MIC. Terr. Atmos. Ocean. Sci., 20, 207-214, doi: 10.3319/ TAO.2008.04.24.02(F3C) IN TRO DUC TIONTo im prove the global weather pre dic tion and space weather mon i tor ing, six microsatellites termed the Formosa Sat el lite 3 -Con stel la tion Ob serv ing Sys tem for Mete orology, Ion o sphere, and Cli mate (FORMOSAT-3/COS MIC; F3/C) were launched into cir cu lar low-earth or bits (LEOs) from Vandenberg Air Force Base, Cal i for nia, at 0140 UTC 15 April 2006. Each microsatellite of the joint Tai wan-US sat el lite con stel la tion mis sion has a GPS occultation experiment (GOX) pay load to op er ate the at mo spheric and ion o spheric ra dio occultation, a tiny ion o spheric pho tom e ter (TIP) to ob serve the night time ion o spheric air glow OI 135.6 nm emis sion (Fig. 1), and a tri-band bea con (TBB) to tomographically es ti mate fine struc tures of ion o spheric electron den sity on the sat el lite-to-re ceiver plane (Rocken et al. 2000;Cheng 2006). While the GOX daily ob serves about 2500 ver ti cal elec tron den sity dis tri bu tions up to the sat ellite al ti tude (Schreiner et al. 2006;Lei et al. 2007;Lin et al. 2007;Lin et al. 2009;Tsai et al. 2009), the TIP pro vides accu rate hor i zon tal gra di ents of night time elec tron den sity Coker et al. 2009;Dymond et al. 2009).The ra dio occultation tech nique was first used by the Mar i ner IV Mars ex plo ra tion mis sion in 1965 ob serv ing Mars' at mo sphere struc tures (Fjeldbo and Eshleman 1968) and later on by Mar i ner V Ve nus mis sion, other plan e tary and lu nar probes, etc. (Fjeldbo et al. 1971;...

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

“…In addition to the RO electron density profiles, the 135.6 nm airglow measurements by TIP have also been used in examining the ionospheric structures. Simultaneous observations of F3/C TIP and GOX have been used to conduct a full space-based (without ground-based receiving stations) ionospheric tomography (Hsu et al 2009) and to study ionospheric auroral oval development (Tsai et al 2010). TIP measures nadir integrated OI 135.6 nm intensities, whereas GOX observes the line-ofsight TEC between the F3/C and GPS satellite.…”

Ionospheric electron content and NmF2 from nighttime OI 135.6 nm intensity

“…Oxygen emissions at 630.0 nm and 777.4 nm have been used to estimate peak electron density as well as F peak altitude [ Tinsley and Bittencourt , 1975; Chandra et al , 1975; Sahai et al , 1981]. However, OI 135.6 nm emission is the one widely used in satellite experiments [ Hicks and Chubb , 1970; Barth and Schaffner , 1970; Mende et al , 2000; Sagawa et al , 2003; Christensen et al , 2003; Kil et al , 2004; Dymond et al , 2000, 2009; Hsu et al , 2009]. The nighttime OI 135.6 nm emission is mainly through the radiative recombination process, and its intensity is hence related to the square of the electron density [ Hanson , 1969; Tinsley and Bittencourt , 1975; Meier , 1991].…”

“… DeMajistre et al [2004] used the Global Ultraviolet Imager (GUVI) 135.6 nm limb images onboard the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite to retrieve nighttime electron density profiles. Recently, Dymond et al [2009] and Hsu et al [2009] reported the electron density profiles using the Tiny Ionospheric Photometer (onboard FORMOSAT‐3 satellites) measurements. The methods followed in these inversions provide the electron density profiles based on a forward model used to simulate the observed data, and are subject to the constraints inherent in the algorithms, and the assumptions and initial conditions involved.…”

Abnormal Signatures Recorded by FORMOSAT-2 and FORMOSAT-3 over South Atlantic Anomaly and Polar Region

“…The TIP is a nadir viewing compact, high sensitive UV photometer onboard the F3/C satellites that measures the integrated OI 135.6 nm intensity along the line-of-sight Hsu et al 2009). TIP can detect even minute intensity variations with a very high sensitivity of about 500 counts second -1 Rayleigh -1 .…”

“…Observations from this track will hence give the airglow signature without any contamination to the detector itself. Note that the ISUAL observations include an upper O( 1 D) layer and a lower OH(9 -3) layer in the limb images (Rajesh et al 2009;Nee et al 2010). The strong O( 1 D) enhancement between 30° -35°S latitudes, occurring below the tangent altitude of 200 km, most likely results from the energetic particle contribution to the emission.…”