Effect of Higher-Order Ionospheric Delay on Precise Orbit Determination of GRACE-FO Based on Satellite-Borne GPS Technique

Ionospheric delay is one of the main errors in precise orbit determination (POD) Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) with satellite-borne GPS technique. Effective elimination or reduction ionospheric can improve POD precision. For dual-frequency data, ionospheric-free linear combination generally used to eliminate first-order term, while igoring influence higher-order terms. To precision GRACE-FO, this paper presents an effective method calculate GRACE-FO observation. Dual-frequency receiver observation total electron content on signal propagation path. The magnetic field strength calculated according international geomagnetic reference model, angle between path calculated. Finally, delays second-order third-order terms are introduced into reduced-dynamic POD. effect analyzed detail. results show that term centimeter level. be improved by adding delay, improvement order sub-millimeter