In-flight calibration and verification of the Planck-LFI instrument

In this paper we discuss the Planck-LFI in-flight calibration campaign.
After a brief overview of the ground test campaigns, we describe in
detail the calibration and performance verification (CPV) phase, carried
out in space during and just after the cool-down of LFI. We discuss in
detail the functionality verification, the tuning of the front-end and
warm electronics, the preliminary performance assessment and the thermal
susceptibility tests. The logic, sequence, goals and results of the
in-flight tests are discussed. All the calibration activities were
successfully carried out and the instrument response was comparable to
the one observed on ground. For some channels the in-flight tuning
activity allowed us to improve significantly the noise performance.