GNSS Receive Antennas on Satellites for Precision Orbit Determination

This paper presents GNSS (Global Navigation Satellite System) antennas developed for different earth observation missions. Such missions often require Precise Orbit Determination (POD). The largest error contribution to POD measurements is usually local multipath, i.e. signals reflected in the satellite structure. Antenna radiation in the back direction must hence be suppressed, while at the same time keep a good coverage at low elevation angles. This is normally achieved by using a standard antenna element placed in a larger choke ring structure. The disadvantage with this arrangement is that the antenna becomes large and relatively heavy. The objective has hence been to develop small and lightweight antennas with low back radiation in combination with good coverage. We have worked with both low profile Patch Excited Cup (PEC), as well as helix antennas. Two of the described antennas are PEC antennas. One smaller, suitable on satellites without large flat mounting areas, and one design where the low elevation gain was traded against the back radiation and a good compromise was achieved using only two narrow choke rings to facilitate mounting on larger flat surfaces. A high-performance conical quadrifilar helix antenna has earlier been developed for applications where a taller antenna can be accommodated