GipsyX/RTGx, A New Tool Set for Space Geodetic Operations and Research

GipsyX/RTGx is the Jet Propulsion Laboratory’s (JPL) next generationsoftware package for positioning, navigation, timing, and Earth science usingmeasurements from three geodetic techniques: Global Navigation Satellite Systems (GNSS), Satellite Laser Ranging (SLR), and Doppler Orbitography andRadiopositioning Integrated by Satellite (DORIS); with Very Long BaselineInterferometry (VLBI) under development. The software facilitates combinedestimation of geodetic and geophysical parameters using a Kalman filter approach on real or simulated data in both post-processing and in real-time. Theestimated parameters include station coordinates and velocities, satellite orbitsand clocks, Earth orientation, ionospheric and tropospheric delays. The software is also capable of full realization of a dynamic terrestrial reference throughanalysis and combination of time series of ground station coordinates.Applying lessons learned from its predecessors, GIPSY-OASIS and RealTime GIPSY (RTG), GipsyX/RTGx was re-designed from the ground up tooffer improved precision, accuracy, usability, and operational flexibility. Wepresent some key aspects of its new architecture, and describe some of its major applications, including Real-time orbit determination and ephemeris predictions in the U.S. Air Force Next Generation GPS Operational Control Segment(OCX), as well as in JPL’s Global Differential GPS (GDGPS) System, supporting User Range Error (URE) of < 5 cm RMS; precision post-processingGNSS orbit determination, including JPL’s contributions to the InternationalGNSS Service (IGS) with URE in the 2 cm RMS range; Precise point positioning(PPP) with ambiguity resolution, both statically and kinematically, for geodeticapplications with 2 mm horizontal, and 6.5 mm vertical repeatability for staticpositioning; Operational orbit and clock determination for Low Earth Orbiting(LEO) satellites, such as NASA’s Gravity Recovery and Climate Experiment(GRACE) mission with GRACE relative clock alignment at the 20 ps level; calibration of radio occultation data from LEO satellites for weather forecastingand climate studies; Satellite Laser Ranging (SLR) to GNSS and LEO satellites,DORIS-based and multi-technique orbit determination for LEO; production ofterrestrial reference frames and Earth rotation parameters in support of JPL’scontribution to the International Terrestrial Reference Frame (ITRF).Keywords: Multi-technique space geodesy, orbit determination andsatellite clocks, Precise Point Positioning (PPP), GNSS, SLR, DORIS2010 MSC: 00-01, 99-00