A compact 500GHz SIS receiver developed for space observations

The submillimeter (submm) regime, ranging from 100 to 1000um, is an important frequency band for radio astronomy. A large number of astronomical spectral lines are located in this frequency region. Compared with ground-based observation, which is limited by the atmospheric absorption of signal, space borne platform provides perfect condition for submm observation. Here we introduce some preliminary results for a compact 500GHz SIS (Superconductor- Insulator-Superconductor) heterodyne receiver system developed for future space borne observation. Considering low power consumption requirement for space applications, we adopt a high critical temperature (Tc) NbN/AlN/NbN SIS tunnel junction for the mixer, a key component of the receiver system, which may work at relatively high temperature around 10 K. All the components, including the SIS mixer, HEMT low noise amplifier and optical lens, are assembled into a compact system. The whole system is cooled by a close-cycled 4K cryo-cooler in laboratory and test result shows a good noise performance, less than 250K at the 500GHz band. Detailed simulation and experimental results will be presented in this paper.