Recent trackings have shown that EL could be offseted easily . We added a simple patch to the tracking algorithm updating the EL position of the target as a function of AZ.
The following picture shows the signal level (dB) received during a standard Moon tracking, (05/06 2015):
The next pictures zoom some parts of the curve:
A perfect system would have exhibit a constant line with random noise, we are far from that. We can observe different plateaus and valleys, some of t hem show a 1-1.5dB loss. We still have unusual right after the apogee. A closer investigation in the logs shows a gap occurring when the reflector changes its direction (up/down). We’ve already seen this on 2D sun tracking pictures (abrupt 0.1° EL changes at the apogee). Periodic oscillations on the signal are related to the tracking mechanism: the antenna stands at a position and sees the target moving across its pointing area. Then it moves to be always slightly ahead. The deeper are these oscillations the larger is the offset. If the radiation pattern of PB8 was exactly aligned to the center of the Moon, the incoming signal should exhibit randomness rather periodic patterns.