In-flight measurement of Planck telescope emissivity


The Planck satellite in orbit mission ended in October 2013. Between the end of Low Frequency Instrument (LFI) routine mission operations and the satellite decommissioning, a dedicated test was also performed to measure the Planck telescope emissivity. The scope of the test was twofold: i) to provide, for the first time in flight, a direct measure of the telescope emissivity; and ii) to evaluate the possible degradation of the emissivity by comparing data taken in flight at the end of mission with those taken during the ground telescope characterization. The emissivity was determined by heating the Planck telescope and disentangling the system temperature excess measured by the LFI radiometers. Results show End of Life (EOL) performance in good agreement with the results from the ground optical tests and from in-flight indirect estimations measured during the Commissioning and Performance Verification (CPV) phase. Methods and results are presented and discussed.

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The Planck Collaboration acknowledges the support of: ESA; CNES, and CNRS/INSU-IN2P3-INP (France); ASI, CNR, and INAF (Italy); NASA and DoE (USA); STFC and UKSA (UK); CSIC, MICINN, and JA (Spain); Tekes, AoF, and CSC (Finland); DLR and MPG (Germany); CSA (Canada); DTU Space (Denmark); SER/SSO (Switzerland); RCN (Norway); SFI (Ireland); FCT/MCTES (Portugal); ERC and PRACE (EU). A description of the Planck Collaboration and a list of its members, indicating which technical or scientific activities they have been involved in, can be found at URL:

The Planck LFI project (including instrument development and operation, data processing and scientific analysis) is developed by an international consortium led by Italy and involving Canada, Finland, Germany, Norway, Spain, Switzerland, UK, and USA. The Italian contribution is funded by the Italian Space Agency (ASI) and INAF.

We want to give special thanks to the Planck Mission Operations Center (MOC) for the professionality and helpfulness shown during the whole Planck mission and, with respect to this work, during the LFI EOL Test Campaign.

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Correspondence to F. Cuttaia.



Table 4 Calibration constants (K/V)

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Cuttaia, F., Terenzi, L., Morgante, G. et al. In-flight measurement of Planck telescope emissivity. Exp Astron 47, 107–127 (2019).

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  • Planck satellite
  • Telescope
  • Emissivity
  • Reflection loss
  • CMB
  • Cosmic microwave background
  • Space instrumentation
  • Microwaves
  • LNA