1D A Software Package Development for Estimating Atmospheric Path Delay based on Numerical Weather Prediction Model Ryuichi ICHIKAWA, Mamoru SEKIDO, and Yasuhiro KOYAMA (KASHIMA SPACE RESEARCH CENTER, NICT) Key words: GNSS, VLBI, atmospheric path delay, numerical weather prediction model, mapping function Abstract Space geodetic positioning systems based on microwave signals, such as the Global Navigation Satellite System (GNSS) and Very Long Baseline Interferometry (VLBI), need to carefully model or cancel the atmospheric path delays in order that these propagation effects do not undermine positioning accuracy. Recently, the development of atmospheric model based on data from numerical weather prediction models have progressed to remove the delays. To apply such atmospheric model for the real correction around Asia monsoon region we have to take account for the highly variable mesoscale disturbances. We have started the development of the software package for estimating the path delays by ray tracing through the output fields of a numerical weather prediction model by Japan Meteorological Agency (JMA). In this paper we describe the preliminary results using the package. 1. GPS GLONASS Galileo (GNSS: Global Satellite Navigation System) 1000km VLBI (Atmospheric Path Delay) GNSS VLBI 1 1 1000 [1] GNSS VLBI EU 1 1 1.2 3 10m
O 1 S G Earth GNSS satellite or Quasar Atmosphere [2] 2. 2. 1 (ray bending) 1 S L L = [n(s) 1]ds + [S G] (1) L G GPS n(s) L s S L ds L c atm c 0 1cm 10m [3] (n 1) 10 6 = K 1(P d /T )+K 2(P v/t )+K 3(P v/t 2 ),(2) P d P v T (hpa) (hpa) (K) K 1 K 2 K 3 [4] [3] (2) (2) (n 1) 10 6 = K 1(P/T ) + K 2(P v/t 2 ) (3) K 2 = (K 2 mk 1)T + K 3. (4) (3) P (hpa) (4) m (4) T (4) mean temperature T m T m = [ (P v/t )dz]/[ (P v/t 2 )dz]. (5) T [5] T m [6] (3) (3) 2. 2 GNSS VLBI
wet delay 5~40cm hydrostatic delay 210~230cm zenith direction 2 Earth mapping function GNSS satellite or Quasar Atmosphere (mapping function) θ L L = L z hm h (θ) + L z wm w(θ), (6) L z h L z w M h (θ) M w(θ) 2 sin(θ) [7] [8] [9] 3. 3. 1 3 ( ) ( 4 ) 2 3. 2 GNSS VLBI [11], [12], [13] 1 m(θ) = a sin θ + b sin θ(or tan θ) + c sin θ + sin θ +... (7) θ a b c GNSS VLBI GNSS VLBI 1300 GPS (GEONET: GPS Earth Observation Network System) 3 [10] 2
4 [10] 1 [10] 5 km 8 / km 2 2 / 60 km 9 4 / 24 km 3.5 4 / 110 km 9 1 / 1 110 km 1 1 / 3 3. 3 10km ( 10km ) [2] 3 2km 00km GNSS VLBI 5 06 9 1 5 km [14] [] ( ) 02 5 6
10 35N km 0 100 0 25 135E 140E 1mm gradient vector cm 5 10 25 30 35 40 Zenith Wet Delay 5 1989 6 29 0 UTC 10km 60 5km 361 289 Fortran MATLAB 4. GPS GLONASS Galileo GNSS 5km 3
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