Facility heterodyne receiver for the Atacama Pathfinder Experiment Telescope

APEX, the Atacama PAthfinder Experiment (APEX) Telescope, is a partnership between Max Planck Institut fur Radioastronomie (in collaboration with Astronomisches Institut Ruhr Universitat Bochum (AIRUB)), Onsala Space Observatory and the European Southern Observatory. The telescope antenna, supplied by VERTEX Antennentechnik, is a 12 m antenna with a 17 mu m rms surface accuracy operating at the Atacama Desert in the Chilean Andes at a 5100 m altitude. The APEX heterodyne facility receiver is placed in the telescope Nasmyth Cabin A. The receivers are coupled to the antenna via relay optics allowing the operation of two different PI-type instruments and a 6-channel facility heterodyne receiver to cover approximately 210-1500 GHz frequency range while providing frequency independent illumination of the secondary. In this report, we present details on the optics for the APEX facility heterodyne receiver and details of its design. The report includes a very brief review of the APEX Band 1, 211-270 GHz, Band 2, 270-370 GHz, Band 3, 385-500 GHz, all based on sideband separation SIS mixer technology and Band T2, 1250 - 1390 GHz, a balanced waveguide HEB mixer, all developed by GARD.