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Fig. 1 | Experimental Astronomy

Fig. 1

From: In-flight calibration of the HIFI diplexers

Fig. 1

Sketch of the optical path of a HIFI diplexer band. Radiation enters from the upper left corner (sky signal: black circle; LO: stylized horn antenna) and is directed to the two mixers at polarizations H and V (depicted as horn antennas on the right-hand side of the Figure). A polarizing grid combines sky and LO and sends two beams to the two diplexers (upper and lower corner of the Figure), each consisting of a polarizing grid and two rooftop mirrors. Before entering the diplexers, the beams are a combination of linearly polarized sky (H and V) and linearly polarized LO (V and H). The goal is to align their polarizations by properly tuning the diplexers. The diplexer layout is depicted in Fig. 2

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