This drawing shows an overview of the Odin radiometer quasioptics. The diplexer tower is at the top right of the drawing and the mixers are below. The cold box is not shown in this drawing.

In the foreground at the bottom is the mirror F2CAL. It's the one with the bite taken out of it. The calibration switch mirror, also called F3CAL, is the circular one seen to the upper left of F2CAL. The load is the box sitting on the plate next to F2CAL.

The big yellow thing in the middle at the bottom of the drawing is one of the star trackers.

The chopper blade is positioned in the beam path. In this configuration, The B and C mixers (555, 572 and 119) are receiving signal from the main beam. The A mixers are on the reference beam (either the calibration load or one of the sky beams).