Kinematic single-frequency relative positioning for LEO formation flying mission

A kinematic GPS-relative navigation estimator has been developed for LEO formation flying applications. In order to accelerate the double-difference integer ambiguity fixing, this estimator processes both the L1 single-frequency code and carrier phase measurements and uses a recursive least-squares approach for improving the float ambiguity accuracy. Actual flight data from SJ-9 formation flying mission performed by China in 2012 are used to assess the estimator performance. The receiver noise and ionospheric effects assessment, the ambiguity resolution as well as the relative positioning performance are investigated. Results show that the proposed algorithm can improve the convergence to the correct ambiguities by 2 or 3 measurement epochs with the local vertical ionospheric delay for each satellite included in the estimator state, and that millimeter level relative positioning precision can benefit from considering differential ionospheric effects.