The optical system is shown in Figure 2a and 2b. The telescope beam emerges
from the elevation flange and passes through a wire grid.
The beam is then reflected down by a flat mirror and comes to a focus
on an offset parabola. The parabola directs the re-focused beam
through a Mylar beamsplitter into the dewar where it is focused into
the mixer feedhorn by a polyethylene lens.
During the receiver commissioning, we measured a main beam efficiency
( 
) of 
on Jupiter.