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The effect of sideband ratio on line intensity for Herschel/HIFI


The Heterodyne Instrument for the Far Infrared (HIFI) on board the Herschel Space Observatory is composed of a set of fourteen double sideband mixers. We discuss the general problem of the sideband ratio (SBR) determination and the impact of an imbalanced sideband ratio on the line calibration in double sideband heterodyne receivers. The HIFI SBR is determined from a combination of data taken during pre-launch gas cell tests and in-flight. The results and some of the calibration artefacts discovered in the gas cell test data are presented here along with some examples of how these effects appear in science data taken in orbit.

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We would like to thank Mihkel Kama from the CHESS team for his help in investigating the sideband ratio effect around the 557 GHz water line. Ronan Higgins would like to thank Netty Honingh for useful discussions on the origins of the sideband ratio imbalance in bands 1 and 2. The authors are grateful to the anonymous referee for valuable comments.

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Correspondence to Ronan Higgins.

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Higgins, R., Teyssier, D., Borys, C. et al. The effect of sideband ratio on line intensity for Herschel/HIFI. Exp Astron 37, 433–452 (2014).

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  • HIFI
  • Herschel
  • Heterodyne
  • Calibration
  • Sideband ratio