Planck 2013 results
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Fig. 9


Compilation of planet and bright point-source positions versus time since the start of the mission. We mark the REBA thermal control adjustment on day 540 with a dashed grey line and the end of the nominal mission (day 563) with a solid grey line. Note the two discontinuities added to the pointing correction model at days 455 and 818. The dashed green line denotes the spline fit to the planet positions used to correct the long-term pointing variations. Left: compilation of measured planet position offsets across the Planck frequencies. Usable planets change by frequency: the blue spectral energy distribution of the planets renders all but Jupiter too dim for required positioning in the LFI frequencies and Jupiter and Saturn positions above 217GHz are compromised due to the nonlinear bolometer response. Right: debiased bright source position offsets in Planck 100217GHz data compared to a trend line fitted to the planet position offsets. Each source was fitted for an apparent position rather than using the catalogued position to measure pointing offset. Two successive observations of the same source have opposite scanning directions, so having the wrong apparent position produces opposite pointing errors that we have corrected.

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