Planck intermediate results. LVII. Joint Planck LFI and HFI data
  processing
  We present the NPIPE processing pipeline, which produces calibrated frequency
maps in temperature and polarization from data from the Planck Low Frequency
Instrument (LFI) and High Frequency Instrument (HFI) using high-performance
computers. NPIPE represents a natural evolution of previous Planck analysis
efforts, and combines some of the most powerful features of the separate LFI
and HFI analysis pipelines. The net effect of the improvements is lower levels
of noise and systematics in both frequency and component maps at essentially
all angular scales, as well as notably improved internal consistency between
the various frequency channels. Based on the NPIPE maps, we present the first
estimate of the Solar dipole determined through component separation across all
nine Planck frequencies. The amplitude is ($3366.6 \pm 2.7$)$\mu$K, consistent
with, albeit slightly higher than, earlier estimates. From the large-scale
polarization data, we derive an updated estimate of the optical depth of
reionization of $\tau = 0.051 \pm 0.006$, which appears robust with respect to
data and sky cuts. There are 600 complete signal, noise and systematics
simulations of the full-frequency and detector-set maps. As a Planck first,
these simulations include full time-domain processing of the beam-convolved CMB
anisotropies. The release of NPIPE maps and simulations is accompanied with a
complete suite of raw and processed time-ordered data and the software,
scripts, auxiliary data, and parameter files needed to improve further on the
analysis and to run matching simulations.
