Program and Abstract Book - SRON

19 th International Symposium on Space Terahertz Technology
4-2
Performance of the superconducting mixers for the HIFI
instrument
Gert de Lange [a] , Jean-Michel Krieg [b] , Netty Honingh [c] ,
Alexandre Karpov [d] , Sergey Cherednichenko [e]
[a] SRON Netherlands Institute for Space Research, Groningen, The Netherlands
[b] LERMA, Paris, France
[c] KOSMA, Cologne, Germany
[d] Caltech, Pasadena, USA
[e] Chalmers, Gothenburg, Sweden
After several years of development and qualification, the HIFI instrument for
the Herschel Space Observatory (HSO) is now at the final stage of integration
and testing. The launch of HSO together with Planck is scheduled for Oct
2008. Once in orbit Herschel will provide a unique window to the submillimeter
and THz frequency range. This frequency range is largely obscured
for ground based astronomy due to the presence of water vapour in the
earth’s atmosphere. Herschel/HIFI will therefore make it possible to do
detailed spectroscopic studies of water lines in the star forming regions of our
galaxy.
The Herschel Space Observatory will fly two cameras/medium resolution
spectrometers (PACS and SPIRE) and the heterodyne instrument HIFI. An
international consortium led by the PI institute, SRON, is building HIFI.
Within HIFI, 7 heterodyne frequency bands cover the spectral range from
480-1250 GHz (SIS mixers) and 1.41-1.91 THz (HEB mixers). Each of these
bands contains two mixers to measure both signal polarizations
simultaneously. The mixer units are built by groups from LERMA (France),
KOSMA (Germany), SRON (Netherlands), Caltech/JPL (USA), and
Chalmers/JPL (Sweden/USA). For frequencies up to 1.1 THz, waveguides and
corrugated horns are used to couple the radiation to the superconducting
mixers. The higher frequency bands make use of planar antennas in
combination with silicon lenses.
For the SIS mixer bands combinations of Nb, NbTiN, ALOx, and AlN junction
technologies are used to optimize the performance within a specific
frequency band. The HEB bands use phonon cooled Nb bolometers that have
been optimized for noise performance, low LO-power consumption and
durability.
In the paper we discuss the design and performance of the HIFI Flight Model
mixer units. We will present the excellent state-of-the-art sensitivities and
the specific design issues that played a role in the development of the
satellite hardware.
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