CoAuthors

Cédric Tourain (CNES, France); Albert Auriol (CNES, France)

The DORIS system measures distances between phase centers of onboard and ground antennas to determine the position of the satellites and their orbits. To this end, the ground antenna phase center position must be known in a terrestrial reference frame. Its position is linked and defined with respect to the Antenna Reference Point (ARP), a conventional physical point for which we assign coordinates.

If the determination of the ARP coordinates is well mastered by IGN, on the other hand, the link with the actual measurement point (phase center) is far more difficult to determine.

Regardless of the need for a good antenna characterization, CNES and IGN jointly worked to initialize an error budget of the ground antenna position subject to uncertainty. With this aim in view, each component was clearly identified to have a separate entry in the budget.

It appeared that the knowledge of the antenna geometry and the guarantee of a good reproducibility in the manufacturing process are essential.

Based on this assumption (today guaranteed by the manufacturer), we decided on new definitions of points, new device and new method to determine the tie vectors.