EMCOR: Development of a european ground-based microwave radiometer to measure stratospheric minor constituents

• Research unit: EU RFP
• Project number: 95.0433

Key words (English)

Microwave radiometry; SIS-Receiver; atmosphere; chlorinemonoxyde

Alternative project number (English)

EU project number: ENV4-CT95-0137

Research programs (English)

EU-programme: 4. Frame Research Programme - 3.1 Environment

Short description (English)

See abstract

Partners and International Organizations (English)

Observatoire de Bordeaux (F), Observatoire de Paris (F),
Observatono Astronómico Nacional and Centro Astronómico de Yebes (E), Rutherford Appleton Laboratory (UK), University of Bremen (D), Helsinki University of Technology (FIN), Institut de Radio Astronomie Millimétrique (F)

Abstract (English)

EMCOR (European Minor Constituent Radiometer) is a heterodyne receiver for the frequency range of 201-210 GHz, whose aim is to measure the emission lines of some stratospheric minor constituents involved in ozone chemistry.
In order to obtain a receiver with a high sensitivity an SIS (Superconductor-Insulator-Superconductor) tunnel junction has been chosen as mixer element. These devices show better mixer performance than Schoffky diodes resulting in a receiver with better signal-to-noise ratio and higher sensitivity. The mixer element is cooled together with the intermediate frequency (IF) amplifier consisting of a high electron mobility transistor (HEMT) in a LHe cryostat down to 4.2 K. Another important aspect for the sensitivity of the system is the calibration. For the measurement of faint spectral lines the balancing mode has been chosen and three different balancing methods have been installed. The quasi optics employ a Gaussian telescope to ensure proper operation over the whole frequency range. A Martin-Pupleff interferometer serves as a side band filter and a baseline wobbler reduces standing waves. The local oscillator (LO) system consists of two Gunn oscillators and a doubler covering a frequency range of 201 to 210 GHz. The LO signal is coupled to the atmospheric signal via a thin Mylar foil serving as a beamsplitter. In the back-end the amplified IF signal is analyzed using an acousto-optical spectrometer (AOS) with 1728 channels and a bandwidth of 1 GHz.
The system has been installed at the International Scientific Station Jungfraujoch (ISSJ) in the Swiss Alps and is currently under testing.

References in databases (English)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 95.0433