We used EutelSat W2 which is seen, at Effelsberg, at azimuth 168 degrees, elevation 32 degrees.
The beacon frequency is 11.7 GHz, with 9 dBW EIRP. It sits in a narrow hole,
10 MHz wide, in the EutelSat spectrum. A 10 MHz bandpass filter
therefore provides a stable environment, independent of the satellite traffic.
The beacon drifted by a few KHz over the course of the experiment.
Eutelsat provided us with very precise satellite ephemerides: the offsets found in our hourly pointing checks were all small. This precision is a serious matter for the holography process, as our imaging is predicated on precise registration of the visibilities on a sky grid centred on the satellite. The EutelSat ephemerides, together with the Effelsberg ability to lock the telescope's coordinate frame to a moving target kept the registration accurate to within a few arcseconds.