MCS Zero Age of Data Measurement Techniques

摘要

Advances in 1999 provided Boeing GPS navigation support contractors the ability to transfer, archive, and manipulate Master Control Station (MCS) Kalman filter data. Since then, these data have been reported in the System Performance Measurement and Analysis (SPMA) quarterly report, and used to assess GPS performance through a variety of metrics, including Zero Age of Data error. This error, in part a byproduct of the real-time, predictive nature of the MCS Kalman filter, affects many navigation and time transfer users. This paper describes the methodology by which the MCS Kalman filter states are compared to truth sources such as NIMA and IGS to calculate Zero Age of Data error. Results show that typical Zero Age of Data errors vary from spacecraft to spacecraft and over time. Also examined are on-orbit frequency standard, ephemeris, and solar events and their associated impacts on Zero Age of Data error. Future efforts to improve Zero Age of Data error are explored. Conclusions reveal that considerable insight is gained by calculating and observing Zero Age of Data characteristics in the effort to understand and reduce this error source in the future.