Galileo, the European global navigation satellite\nsystem, is in its in-orbit validation phase and the four\nsatellites which have been available for some months now\nhave allowed a preliminary analysis of the system performance.\nPrevious studies have showed that Galileo will be\nable to provide pseudorange measurements more accurate\nthan those provided by GPS. However, a similar improvement\nwas not found for pseudorange rate observations\nin the velocity domain. This fact stimulated additional\nanalysis of the velocity domain, and, in particular, an unintended\noscillatory component was identified as the main\nerror source in the velocity solution. The magnitude of\nsuch oscillation is less than 10 cm/s, and its period is in the\norder of few minutes. A methodology was developed to\nidentify oscillatory components in the Galileo IOV pseudorange\nrate observables, and it was verified that the\nmeasurements from Galileo IOV PFM and Galileo IOV\nFM2 are affected by a small oscillatory disturbance. This\ndisturbance stems from the architecture adopted for combining\nthe frequency references provided by the two active\nclocks present in the Galileo satellites. The issue has been\nsolved in Galileo IOV FM3 and Galileo IOV FM4, and the\noscillatory component has been eliminated. We also propose\na methodology for removing this unwanted component\nfrom the final velocity solution and for determining\nthe performance that Galileo will be able to achieve. The\nanalysis shows that Galileo velocity solution will provide a\nroot-mean-square error of about 8 cm/s even in the limited\ngeometry conditions achieved using only four satellites.\nThis shows the potential of Galileo also in the determination\nof user velocity.
Loading....