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| Titel |
PHOCUS radiometer |
| VerfasserIn |
O. Nyström, D. Murtagh, V. Belitsky |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 5, no. 6 ; Nr. 5, no. 6 (2012-06-15), S.1359-1373 |
| Datensatznummer |
250002970
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| Publikation (Nr.) |
 copernicus.org/amt-5-1359-2012.pdf |
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| Zusammenfassung |
PHOCUS – Particles, Hydrogen and Oxygen Chemistry in the Upper Summer Mesosphere
is a Swedish sounding rocket experiment, launched in
July 2011, with the main goal of investigating the upper atmosphere in the
altitude range 50–110 km. This paper describes the SondRad instrument in the
PHOCUS payload, a radiometer comprising two frequency channels (183 GHz
and 557 GHz) aimed at exploring the water vapour concentration distribution
in connection with the appearance of noctilucent (night shining) clouds. The
design of the radiometer system has been done in a collaboration between
Omnisys Instruments AB and the Group for Advanced Receiver Development
(GARD) at Chalmers University of Technology where Omnisys was responsible
for the overall design, implementation, and verification of the radiometers
and backend, whereas GARD was responsible for the radiometer optics and
calibration systems.
The SondRad instrument covers the water absorption lines at 183 GHz and 557 GHz.
The 183 GHz channel is a side-looking radiometer, while the 557 GHz
radiometer is placed along the rocket axis looking in the forward direction.
Both channels employ sub-harmonically pumped Schottky mixers and Fast
Fourier Transform Spectrometers (FFTS) backends with 67 kHz resolution.
The radiometers include novel calibration systems specifically adjusted for
use with each frequency channel. The 183 GHz channel employs a continuous
wave CW pilot signal calibrating the entire receiving chain, while the
intermediate frequency chain (the IF-chain) of the 557 GHz channel is
calibrated by injecting a signal from a reference noise source through a
directional coupler.
The instrument collected complete spectra for both the 183 GHz and the 557 GHz
with 300 Hz data rate for the 183 GHz channel and 10 Hz data rate for
the 557 GHz channel for about 60 s reaching the apogee of the flight
trajectory and 100 s after that. With lossless data compression using
variable resolution over the spectrum, the data set was reduced to 2 × 12
MByte.
The first results indicate that the instrument successfully performed
measurements of the mesospheric water profile as planned. However, the
temperature environment for the instruments showed more extreme behaviour
than expected and accounted for. Consequently, the results of the calibration
and the final data reduction will need careful treatment. Further,
simulations through finite element method (FEM), modelling and direct
measurements of the simulated thermal environment and its impact on the
instrument performance are described, as well as suggestions for
improvements in the design for future flights. |
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