Planck Early Results. V. The Low Frequency Instrument data processing
  We describe the processing of data from the Low Frequency Instrument (LFI)
used in production of the Planck Early Release Compact Source Catalogue
(ERCSC). In particular, we discuss the steps involved in reducing the data from
telemetry packets to cleaned, calibrated, time-ordered data (TOD) and frequency
maps. Data are continuously calibrated using the modulation of the temperature
of the cosmic microwave background radiation induced by the motion of the
spacecraft. Noise properties are estimated from TOD from which the sky signal
has been removed using a generalized least square map-making algorithm.
Measured 1/f noise knee-frequencies range from 100mHz at 30GHz to a few tens of
mHz at 70GHz. A destriping code (Madam) is employed to combine radiometric data
and pointing information into sky maps, minimizing the variance of correlated
noise. Noise covariance matrices required to compute statistical uncertainties
on LFI and Planck products are also produced. Main beams are estimated down to
the approx -10dB level using Jupiter transits, which are also used for
geometrical calibration of the focal plane.
