2006A&A...454L..17R

The new APEX telescope, located on Llano Chajnantor in Northern Chile, will have high resolution spectroscopic instruments covering the wavelength region from 0.20 to 1.30mm (210-1500GHz). In May 2005, the first facility receiver for the band 0.79-1.07mm (279-381GHz) was installed together with backends providing down to 60kHz spectral resolution. This instrument that operates in double sideband mode uses superconducting tunnel junctions (SIS) as mixing elements operating at 4K to achieve close to quantum-limited noise performances. The receiver is cooled by a closed-cycle cooling machine that allows continuous operation. The receiver design minimizes moving parts and is fully operated by remote to improve its reliability and the ease of use. The double sideband (DSB) receiver temperatures are in the range 50-70K, which typically results in a DSB system noise temperature of about 100K in excellent weather conditions and between 100-200K in good weather conditions.