EMCOR radiometer: calibration and first tests

The objective of the European project EMCOR was the development of a heterodyne receiver for the frequency range of 201 to 210 GHz for the measurement of the amounts of various minor constituents of the stratosphere involved in ozone chemistry. In order to be able to measure even very faint spectral lines a superconducting tunnel junction has been chosen as mixer element. Additionally, special care has been taken in developing the calibration unit of the system. Besides the classical hot-cold calibration three different balancing methods can be employed: a beam-switch technique with an atmospheric reference signal, a beam switch technique with a reference signal from a variable reference load or a frequency switch technique. The system has been integrated and is currently under testing. It will be installed at the International Scientific Station Jungfraujoch in he Swiss Alps and operated within the framework of the European Alpine stations of the Network for the Detection of Stratospheric Change.