Presentation Information
[U06-05]Japanese Precise Orbit Determination for GNSS satellites and its Contributions for High Precision Positioning Society★Invited Papers
*Satoshi Abe1, Takayuki Miyazaki1, Koki Yoshinaga1, Masanori Yokokawa1, Kyohei Akiyama2, Emi Imada2 (1.Geospatial Information Authority of Japan, 2.Japan Aerospace Exploration Agency)
Keywords:
JGX,IGS Analysis Center,GNSS,QZSS,Precise Orbit Determination
GNSS (Global Navigation Satellite System) is an indispensable infrastructure for modern society to secure stable access to globally consistent geocentric coordinates. In the past, centimeter-level precise positioning by multiple-GNSS including GPS, GLONASS, Galileo, QZSS was mainly utilized by the scientific or land survey community since the Double Difference (DD) processing method is too complicated for the most of non-experts. Now, however, newly emerging techniques such as Precise Point Positioning (PPP) allow more people to access precise position through GNSS positioning.
Precise Orbit Determination (POD) is a key enabler to realize precise positioning, especially for PPP. Unlike DD-solutions, PPP cannot cancel out errors of satellites’ orbits and clocks. These errors must be estimated prior to PPP processing independently.
The IGS (International GNSS Service) provides the most reliable orbit and clock error(ephemeris) information of GNSS satellites. Academic and government organizations in eight countries voluntarily estimate precise ephemeris of GNSS satellites in parallel and provide their products to IGS. These organizations are called Analysis Centers (ACs). IGS ACC (AC Coordinator) combines the individual precise ephemeris products to generate the IGS combined products and the IGS publishes them via online IGS Data Centers.
IGS adopted a joint body of GSI (GeoSpatial Information Authority of Japan) and JAXA (Japan Aerospace eXploration Agency) as the new IGS AC identified by JGX in December 2023. JAXA has started development of fully original POD software MADOCA since 2011. GSI has operated Japanese CORS (Continuous Observing Reference Station) network, GEONET and processed the data to generate daily solutions since 1990s.
JAXA shares MADOCA and related POD expertise to GSI, and GSI takes the role of daily operation of processing to generates JGX ephemeris products and share findings obtained through the daily operation with JAXA. JGX products are submitted to IGS and integrated into the IGS combined products. JGX products are processed with fully original POD software and thus could contribute to the IGS as fully independent solution with is valuable for validation of the IGS products. On the other hand, JGX products have been evaluated through comparison with IGS products and the evaluation helps JGX to identify error sources of inconsistency.
Many of processing functions in MADOCA have been improved to achieve higher POD performance. For example, functions newly implemented in MADOCA are: physical models of GNSS satellites (solar radiation pressure, albedo, and antenna thrust), minimum constraints to reference coordinates, more consistent Earth Rotation Parameter (ERP) model (sub-daily parameter, zonal-tide model), advanced observation model (higher order ionospheric delay of GNSS signal, Shapiro delay caused by general relativity effect) and widely supported data ( multi GNSS, and frequency, latest data format for SINEX). We will review impacts of these recent improvements in this presentation.
As a results of the efforts described above, JGX products achieve quite comparable performance to the IGS combined products.
The priority of JGX team is improvement of performance of JGX products. In addition, QZSS precise ephemeris as IGS official product is another priority. Monitoring of performance and quality of the products are critical to achieve these priorities, and further collaboration with related stakeholders in and outside of Japan is also a key to move forward.
Precise Orbit Determination (POD) is a key enabler to realize precise positioning, especially for PPP. Unlike DD-solutions, PPP cannot cancel out errors of satellites’ orbits and clocks. These errors must be estimated prior to PPP processing independently.
The IGS (International GNSS Service) provides the most reliable orbit and clock error(ephemeris) information of GNSS satellites. Academic and government organizations in eight countries voluntarily estimate precise ephemeris of GNSS satellites in parallel and provide their products to IGS. These organizations are called Analysis Centers (ACs). IGS ACC (AC Coordinator) combines the individual precise ephemeris products to generate the IGS combined products and the IGS publishes them via online IGS Data Centers.
IGS adopted a joint body of GSI (GeoSpatial Information Authority of Japan) and JAXA (Japan Aerospace eXploration Agency) as the new IGS AC identified by JGX in December 2023. JAXA has started development of fully original POD software MADOCA since 2011. GSI has operated Japanese CORS (Continuous Observing Reference Station) network, GEONET and processed the data to generate daily solutions since 1990s.
JAXA shares MADOCA and related POD expertise to GSI, and GSI takes the role of daily operation of processing to generates JGX ephemeris products and share findings obtained through the daily operation with JAXA. JGX products are submitted to IGS and integrated into the IGS combined products. JGX products are processed with fully original POD software and thus could contribute to the IGS as fully independent solution with is valuable for validation of the IGS products. On the other hand, JGX products have been evaluated through comparison with IGS products and the evaluation helps JGX to identify error sources of inconsistency.
Many of processing functions in MADOCA have been improved to achieve higher POD performance. For example, functions newly implemented in MADOCA are: physical models of GNSS satellites (solar radiation pressure, albedo, and antenna thrust), minimum constraints to reference coordinates, more consistent Earth Rotation Parameter (ERP) model (sub-daily parameter, zonal-tide model), advanced observation model (higher order ionospheric delay of GNSS signal, Shapiro delay caused by general relativity effect) and widely supported data ( multi GNSS, and frequency, latest data format for SINEX). We will review impacts of these recent improvements in this presentation.
As a results of the efforts described above, JGX products achieve quite comparable performance to the IGS combined products.
The priority of JGX team is improvement of performance of JGX products. In addition, QZSS precise ephemeris as IGS official product is another priority. Monitoring of performance and quality of the products are critical to achieve these priorities, and further collaboration with related stakeholders in and outside of Japan is also a key to move forward.