Preliminary evaluation of the impact of temperature fluctuations in the HFI 4K stage on LFI

Abstract

In this technical note we provide a preliminary analysis of the effect of temperature fluctuations at the level of the HFI 4K stage on the scientific performances of the Planck-LFI instrument. The stability of this stage is of crucial importance for the LFI, as it impact directly the stability of the measured signal through its reference load. The availability of the first simulations of the 4K temperature stability from the HFI team has prompted a quick assessment of the expected effect, which is found to be large enough to require the application of software removal algorithms to maintain the residual effect in the final maps within the required levels. Clearly it is of crucial importance the availability in a short time of measurements from the HFI 4K cooler in order to be able to perform robust estimates of the final expected systematic effect.