Simultaneous estimation of GPS P1P2 differential code biases using low earth orbit satellites data from two different orbit heights
Abstract
Global navigation satellite system (GNSS) differential code bias (DCB) is a significant error source in ionosphere modeling that uses GNSS observation data. Given that the orbit altitudes of low earth orbit (LEO) satellites are above the F layer of ionosphere, ionized electrons come from the upper ionosphere or plasmasphere, so observations suffer from small signal delays. DCBs can be estimated using LEO data instead of that from ground stations. In most studies, LEObased DCB estimation employs onboard data from either a single LEO or from two that are at the same orbit height. In our study, we applied four LEO satellites data from two different orbit heights to estimate GPS satellite DCBs, receiver DCBs and LEObased vertical total electron content (VTEC) parameters simultaneously. Before DCB estimation, a data preprocessing strategy suitable for LEO onboard data was applied to obtain clear pseudorange data. We developed a processing method for the upper ionosphere using LEO onboard data from different orbit heights, by introducing LEObased VTEC models in advance to remove its effects; two introduced VTEC models were derived from modeling results using paired data from the same orbital height, respectively. We draw some conclusions as follows. For the LEO satellites at different orbit heights, the more the number of LEO satellites involved, the more stable estimation results achieved. We also noted that the GPS satellite DCBs stability and accuracy with established LEObased VTEC models, using multiLEOs data from different orbit heights, were better than the achievable results using onboard data from the same orbital height or using single LEO satellite schemes. Compared with the estimation results of single LEO solutions, the monthly stabilities and accuracies for multiLEOs solutions from different orbit heights are improved by 2535% approximately. Among all the tested schemes, superior stability derived from simultaneous estimation using four LEO data at different orbit heights is 0.064 ns; the optimal accuracies for DCB estimation for different GPS satellites are the scheme GRACEA and JASON2 (two LEOs) of 0.146 ns, approximately, compared with Center of Orbit Determination of Europe products, respectively. The stability and accuracy of LEObased DCB estimations were approximately similar to those achieved using ground solutions.
 Publication:

Journal of Geodesy
 Pub Date:
 December 2020
 DOI:
 10.1007/s00190020014585
 Bibcode:
 2020JGeod..94..121L
 Keywords:

 Low earth orbit satellite (LEO);
 Onboard GNSS/GPS data;
 GPS satellite differential code bias (DCB);
 Onboard receiver differential code biases (DCB);
 Different orbit heights;
 LEObased vertical total electron content (VTEC);
 Stability and accuracy