Using FORMOSAT-3/COSMIC GPS data to
improve the La Plata Ionospheric Model
J. Federico Conte, Francisco
Azpilicueta, Claudio Brunini, Diego
Janches
GESA, Facultad de Ciencias Astronómicas
y Geofísicas, UNLP
NASA
Second LISN Workshop
São José dos Campos, Brasil
November 7 – 11, 2011
Abstract
In the framework of the AIRES (Argentine Ionospheric Radar Experiment Station)
Project, we are currently upgrading the La Plata Ionospheric Model (Brunini et
al., 2011b). Inspired by the IRI model (Bilitza, 2002) and based on the Jones &
Gallet (1962) mapping technique, after a process of data assimilation is applied,
this semi-empirical model is capable of reproducing electron density profiles
dependent on the Universal Time, the geographical location and the solar
activity level. At the moment, the data assimilation technique only processes the
raw-data obtained from ground-based dual-frequency GPS measurements.
Nevertheless, the model is also capable to incorporate FORMOSAT-3/COSMIC
electron density profiles externally calculated which, combined with the
ionospheric information obtained from the ground-based GPS measurements
are used to correct the coefficients of the Jones & Gallet formulation.
Consequently, we are currently analyzing and pre-processing GPS raw-data from
the FORMOSAT-3/COSMIC mission and appropriately modifying our model in
order to incorporate this data to our formulation to have a better description of
the electron density profile, especially for the top-side region of the ionosphere.
Second LISN Workshop, São José dos Campos, Brasil, November 7-11, 2011
Conte et al. 2
La Plata Ionospheric Model (LPIM)
 Semi-empirical model developed by Prof. Brunini (Brunini, 1998)
 Continuously updated and upgraded by Brunini’s group (e.g., Azpilicueta et
al., 2006)
 Originally, LPIM was capable of reproducing global (local) TEC maps using
ground-based dual-frequency GPS raw data from approx. 300 (a particular)
IGS stations.
Second LISN Workshop, São José dos Campos, Brasil, November 7-11, 2011
Conte et al. 3
Current version of La Plata Ionospheric
Model
 Now, besides computing global or local TEC maps, the model is also capable
of reproducing electron density (ED) profiles for the whole ionosphere
(Brunini et al., 2011a).
 Following a similar procedure to that implemented by IRI (Bilitza, 2002), the
LPIM implements the Jones & Gallet formulation to represent the
geographical (latitude and longitude) and daily (UT) variations of the F2 peak
parameters, HmF2 (M3000F2) and NmF2 (f0F2).
 The electron densities (critical frequencies) and heights of the E and F1
ionospheric layers are estimated following the CCIR recommendations (CCIR,
1991). Also, the scale heights of the E, F1 and F2 layers are computed
according to the CCIR recommendations.
 Four Chapman layers are adjusted using actual ground-based dual-frequency
GPS raw data and externally calculated ED profiles.
Second LISN Workshop, São José dos Campos, Brasil, November 7-11, 2011
Conte et al. 4
Current version of La Plata Ionospheric
Model
N (h)  Nm exp[k  (1  z  exp(z)]
h  hm
z
H
 Depending on the description of the electron loss process, the factor k can
be 0.5 or 1.
 According to Bilitza (2002), most modelers have found that 0.5 provides a
better match with observations; and according to that experience, LPIM’s
formulation uses that value.
 The top-side profile of the LPIM is represented with an α-Chapman (k=0,5)
function with height-varying scale height (Reinisch and Huang, 2001).
Second LISN Workshop, São José dos Campos, Brasil, November 7-11, 2011
Conte et al. 5
Current version of La Plata Ionospheric
Model
In summary, the LPIM ED profile is given by a function that depends on two
sets of constants but unknown parameters:
N ( ,  , h, t ,U JG ,U p )
Finally, LPIM uses the Least Square method to daily estimate the
parameters aforementioned together with the satellite and receivers DCBs:
N
N
d   U p  
d   B s  BR  
 U JG 0
 U p
L4  sTEC0  U JG  
0
Second LISN Workshop, São José dos Campos, Brasil, November 7-11, 2011
Conte et al. 6
Current version of La Plata Ionospheric
Model
Brunini et al., 2011a
Second LISN Workshop, São José dos Campos, Brasil, November 7-11, 2011
Conte et al. 7
FORMOSAT-3/COSMIC
 Constellation Observing System for Meteorology,
Ionosphere, and Climate.
 Joint Taiwan-US constellation of six satellites
orbiting at around 800 km of altitude.
 Payload consisting of three instruments:
I. GPS occultation experiment (GOX).
II. Ionospheric photometer to study
nighttime airglow emission.
III. Tri-band beacon (TBB) to
tomographically estimate ionospheric
fine structures.
 GPS occultation experiment: two POD antennas,
and two Occultation antennas distributed in a
diamond configuration.
Second LISN Workshop, São José dos Campos, Brasil, November 7-11, 2011
Conte et al. 8
Work in progress
At present, we are adapting
our model so it can
process, together with
ground-based GPS
measurements, the dualfrequency raw data
obtained from the GPS
receivers onboard the
FORMOSAT-3/COSMIC
mission.
Second LISN Workshop, São José dos Campos, Brasil, November 7-11, 2011
Conte et al. 9
References
-Azpilicueta F, Brunini C, Radicella SM (2006) Global ionospheric maps from GPS observations using
modip latitude. Adv Space Res, 38(11): 2324-2331. doi:10.1016/j.asr.2005.07.069.
- Bilitza D, Sheik NM, Eyfrig R (1979) A global model for the height of the F2-peak using M3000 values
from CCIR. Telecommunication Journal, 46: 549-553.
-Bilitza D (2002) Ionospheric Models for Radio Propagation Studies. In: Review of Radio Science 19992002, 625-679, Oxford University Press.
-Brunini, Claudio: Global Ionospheric Model from GPS measurements. Tesis Doctoral. Facultad de
Ciencias Astronómicas y Geofísicas de La Plata, 1998.
- Brunini C, Azpilicueta F, Gende M, Aragón-Ángel A, Hernández-Pajares M, Juan JM, Sanz J (2011a)
Toward a SIRGAS service for mapping the ionosphere’s electron density distribution. In Pacino et al.
(eds): Geodesy for Planet Earth, IAG Symposia, 135:575-580.
-Brunini C, Azpilicueta F, Gende M, Camilión E, Aragón-Ángel A, Hernández-Pajares M, Juan M, Sanz J,
Salazar D (2011b) Ground- and space-based GPS data ingestion into the NeQuick model. J Geod (in
press).
- CCIR (1991) Report 340-6. Comité Consultatif International des Radio communications, Genève,
Switzerland.
- Chapman S (1931) The absorption and dissociative or ionizing effect of monochromatic radiation in an
atmosphere on a rotating Earth. Proceedings of the Physical Society, 43: 483-501.
- Dudeney JR (1974) A simple empirical method for estimating the height of the F2-layer at the
Argentine Islands Graham Land. Science Report Nº 88, London, UK, British Antarctic Survey.
- Jones WB, Gallet RM (1962) Representation of diurnal and geographical variations of Ionospheric data
by numerical methods. Telecommunication Journal, 29: 129-149.
- Reinisch BW, Huang X (2001) Deducing top-side profiles and total electron content from bottom-side
ionograms. Adv Space Res, 27(1): 23-30.
Second LISN Workshop, São José dos Campos, Brasil, November 7-11, 2011
Conte et al. 10