SHeFI

The Swedish Heterodyne Facility Instrument (SHeFI) was built by the GARD group at the Chalmers University, Sweden, with the Onsala Space Observatory and mounted on the Atacama Pathfinder Experiment (APEX) telescope on the Chajnantor plateau, in Chile’s Atacama region in 2008.

The SHeFI instrument was set up at the Nasmyth-A focus of APEX and consists of four wideband heterodyne receiver channels for 1.30 mm (230 GHz — APEX–1), 0.87 mm (345 GHz — APEX–2), 0.65 mm (460 GHz — APEX–3), and 0.23 mm (1300 GHz — APEX–T2). All the bands were located inside a single closed-cycle cryostat which maintained the coldest part at a temperature close to -269 °C. APEX–1, APEX–2 and APEX–3 employed superconductor-insulator-superconductor (SIS) mixers and behaved as single sideband receivers (SSB). APEX–T2 was built using hot bolometer (HEB) mixer technology and was a double sideband receiver (DSB).

The receiver was built to replace APEX–2A and was based on an integrated design concept where no plugged modules or cartridges are used. Instead, the receiver provided tight integration of all components, which saved space and reduced the mass. All receiver channels were connected to the antenna via an optical switch, a mirror in the centre of the SHeFI top cover rotated by a step motor.

The SHeFI instrument was decommissioned in October 2017.