CAD drawing (with the fiberglass spacer rings omitted) and photograph of the assembled receiver. The optics assembly contains the top part (M4/5), bottom part (M3), beam splitter (BS), polarizing grid (GR) and the mixers (MX). Further down on the 4 K level are the bias network boxes (BN), isolators (ISO), and LNAs (LNA). On the 15 K level are the LO infrared blocking filters (F3). The 110 K level contains the LO multipliers (LO) with associated mirrors (M6). Finally, on the 300 K level (the vacuum flange) reside the ESD protection board (ESD) on top of the DC feedthroughs (DC-FT), and the LO feedthroughs (LO-FT) and IF feedthroughs (IF-FT). The LO waveguide (WG) contains a stainless-steel thermal break.