Developing RIM to Validate the Space Observation

1
Developing RIM to Validate the Space Observation
2004.03.4-5, Tsukuba, Ibaraki

• J. Ping K. Matsumoto
• National Astronomical Observatory
• Saito
• Kyoto University

2
What Kinds of Models We Have ?
Knowledge of the ionospheric electron density is
essential for a wide range of applications,
e.g., radio and telecommunications, satellite
tracking, and Earth observation from space.
TEC Models (Quite, Stable, Large Scale, Seasonal
average) Phenomenological Chiu model, the Bent
mode (for satellite tracking), the
semi-empirical SLIM model (theoretically obtained
grid values), FAIM model (Chiu formalism SLIM
results). The Empirical International Reference
Ionosphere (IRI) model, which having undergone
gt20 decades of scrutiny and improvement.
3
IRI Profile TEC Global Map
IRI90?IRI95?IRI2001 (2003 version) http//nssdc.g
sfc.nasa.gov/space /model/ionos/iri.html
Zenith direction Maximum 200TECu (Fixed to the
direction Of the Sun) Minimum 1TECu
1TECu 1016 m-2
F2
F1
E
D
4
Ionosphere Observation methods Non-coherent
disperser radar Ionosonder optical camera
particle counter Multi frequency obs. by space
methods Faradii Rotation by observing
geo-stationary s/c Very Long Baseline
Interferometry GPS !!!!!! Sea Surface
Altimetry Satellite (T/P, Jason-1 !!!)
5
Why using space methods? High precision, high
time and spatial resolution to monitor the fast
variation storm, TID, scintillation other
events to look for precursor for earthquake?
Space weather forecast ?
S/C Pass
6
How Does GPS Do IT
Thin Shell Ionosphere Model with GPS
VTEC(?,d,H)TEC(?,d,H)/Mapping Function
Slant
Ht600km
Hb300km
GPS Code P, C/A, Phase Slant TEC(?,d,H)Phase
Delay 40.3-1(1/f22-1/f12) 1 )(L1-L2) Or
Group Delay 40.3-1(1/f22-1/f12) 1 )(P2-P1)
7
Who is modeling TEC by using GPS methods

• Global TEC model IGS ionospheric TEC
  working group
• CODE, JPL, EMRG, ESAG
• http//www.aiub.unibe.ch/ionosphere.html
• Regional TEC model
• North America, Europe, Japan
• http//www.nwra-az.com/ionoscint/sp_main.html
• Local model DSN of JPL, TECmeter site,
• independent institutes researchers

8
Modeling Global VTEC (GIM)

• Models spherical harmonic function, IONEX
• thin shell, 1model/2hr 8x8?12x8?15x15

ß-- the geocentric latitude of the intersection
point of the line receiver-satellite with the
ionospheric layer,
s -- the sun-fixed longitude of the ionospheric
pierce point,
LT--the local solar time, UT --Universal Time.
FTP//
ftp.unibe.ch/CODE
9
GPS P1/C1-C2 Code Biases
Key Point on this work To solve the differential
code biases reasonably and precisely, and to
remove it clearly from the observation
data,various algorithms are developed.
GPS PCB of JPL From 0 differential obs.
GNSS PCB of CODE
From double differential observable
10
Modeling GEONET TEC
Step 1, Estimating relative/absolute TEC from GPS
dual frequency phase and code observable
Independent method to estimate DCB. Step 2,
Making the GEONET TEC map with various time
scale, and estimating regional TEC model based
on GIM of the same dat Step 3, Expanding it to
spherical function 60x60 (or higher) orders and
degrees (Ping, et al., 2002) for 10 (or shorter)
minutes obs.
Merge RIM into GIM
A. Saito
11
Regional Ionosphere Map (RIM) based on GEONET TEC

• Models spherical harmonic function, 60x60
• Time and spatial resolution 10min, 3o
• Time and spatial coverage 24hr/day, belt
• Errors 0.5-1 TECU (5-10cm_at_S-Band)
• Advantage Large and Medium Scale Variation
• Short comes 1. Limited instantaneous spatial
  coverage. about 20x20 square degree

12
T/P Jason-1 Nadir TEC vs GIM/RIM
Topex/Poseidon is launched on August 10, 1992.
It was designed to fly for three to five years,
but have flied for 11 years.
As T/P following on SSH Mission, Jason-1
Launched on 12/07/02. Dual frequency
Altimetry C- Ku- Bands Nadir TEC being
measured point by point.
13
T/PJason Nadir TEC
Eccentricity 0.00080 Inclination 66.0440 Mean
Height 1,335 km
All Nadir TEC over sea !!! One Cycle10days
TEC in Geographical in Solar
Geomagnetic Frame It needs 80-120 days TEC data
to cover the solar-geomagnetic frame globally.
14
Along Track Point by Point TEC??
GIM - Jason
???????
GIM vs T/P
GIM - T/P
15
Validate T/P-Jason by RIM
T/P-GIM 4TECu Jason-T/P 1.42 TECu Jason-RIM
0.73TECu
16
GIM/RIM vs VLBI
Differential TEC at QSO directions can be
obtained by VLBI dual frequency S/X-bands
observation. However, the biases and drifts of
VLBI TEC are too large compare with GIM/RIM,
i.e. 4.7 TECu for KSP Kashima-Koganei Baseline,
and gt150TECu for JADE Tsukuba-Aira
Baseline. This biases can be corrected by
GIM/RIM.
17
Summary By using GPS GIM/RIM method, not
only the ionosphere delay for space techniques
can be corrected, but the delay biases due to
instruments at different frequencies are also
highly possible to be validated, if the
received duel- or multi-frequency radio signals
pass through the Earth ionosphere. For the
future research of this topic, global VLBI,
CHAMP SST, the gravity mission of Japan,
RISE/SELENE s/c VLBI Tracking, as well as other
space techniques will be involved into
calibration program using GIM/RIM TEC.
Thank you for join in !