Planck pre-launch status : HFI ground calibration

Context. The Planck satellite was successfully launched on May 14th 2009. The pre-launch calibration measurements of the High Frequency Instrument (HFI) on board Planck and their processing have been completed. Aims. The pre-launch calibration of HFI has multiple objectives. First, it determines instrumental parameters that cannot be measured in-flight and predicts parameters that can be measured in-flight. Second, it is a unique opportunity to operate and understand the instrument under an wide range of anticipated operating conditions. Finally, it provides an estimate of the performance of the instrument as built. Methods. The pre-launch calibration results from characterisations at the component and subsystem levels, from the focal plane calibrations carried out at IAS (Orsay) in the Saturne simulator, and from the tests at the satellite level carried out in the CSL (Liege) cryogenic vacuum chamber. Models allow an estimate the instrument pre-launch parameters when no measurement can be performed. Results. The Planck-HFI instrument characteristics and behavior are now well measured and the flight nominal setting of all parameters has been determined. The expected in-flight performance exceeds the requirements and is close to or better than the goal specifications.