Agenda/Notes from Systematics WG telecon July 19 2017

on the call: Brendan, Paolo, Colin, Julian, Shaul, Maurizio, Joy

  - S4 tools (Colin)
      * S4 doesn't yet have an instrument design, so at this point, they are considering generic "additive systematics" == something that adds additional B-mode power and could bias a measurment of "r"
      *  A generic noise-like systematic (not rolled off by beam) is considered
      * Looked at an "uncorrelated" systematic (i.e. uncorrelated from band to band) such as residual beam mismatch: a white and a 1/ell version
      * Also looked at a correlated systematic which can bias cross-spectra, same amplitude (in CMB units) in all bands (i.e. looks like a CMB fluctuation)
      * Going back to Fischer forecast, including foreground separation in frequency space: can write down what level of systematic corresponds to as a bias in "r" of 1e-4 (target of sigma_r in 5e-4)
      * Colin is now applying this to the S4 data challenge.  
      * Longer term this is meant to provide a benchmark to judge systematics against as a real instrument design takes shape.
      * What do we need in order to perform this type of analysis for the CMB probe Imager, given our set of bands and noise levels?
        * Can be done just with map noise and frequency bands: though of course it assumes an analysis method  based on BICEP/Kick which may or may not be applicable to a full-sky analysis.
        * Also noise shape for a full-sky mission is likely to be quite different.  Atmosphere enters in as an ell_knee
        * Simple parameterization for foreground estimation: probably fine for ~3% sky, but for Probe would use a full-sky template fit.
        * Julian points out that there will be a map-based analysis within S4 that will perhaps test this applicability.  The more pixels that are available for a full-sky map, a maximum likelihood starts to become computationally expensive.
  - Planck low ell polarization paper [[https://www.aanda.org/articles/aa/full_html/2016/12/aa28890-16/aa28890-16.html|Planck intermediate results XLVI. Reduction of large-scale systematic effects in HFI polarization maps and estimation of the reionization optical depth]] (Brendan)
      * Summary plots
        * Fig 17: estimates of HFI systematic errors in EE auto-spectra vs. projected noise
        * Fig 18: null tests of HFI detectors
        * Fig 23: LFI systematic errors
      * Specific plots
        * Fig 2: noise PSDs and CSDs: correlated cosmic ray hits; Fig A.1 shows this propagated to TT/EE/BB residuals.
        * Fig 4: HFI far sidelobe pickup: propagated physical optics models.  (note: Physical optics models were not incredibly accurate)
        * Fig 9: residual ADC nonlinearity with gain correction leaves low ell polarization residuals: see Fig B.13 for what it looks like on the sky
        * Fig 10: "Empirical transfer function" unknown systematic
        * Fig 13: relative (detector to detector) gain measured from dipole to better than 1e-5 level
        * Fig 14: ground-based vs. sky-based bandpass leakage correction
        * Fig 30: estimated foreground residuals in HFI
        * Fig A.2: HFI warm readout drifts propagated to residual power spectra
        *     
  -   [[preliminary_list_of_systematic_effects_to_consider|Systematics List]] (Ranajoy, Joy) {{::types_of_systematics.pdf|}}
  - CORE systematics paper  [[https://arxiv.org/pdf/1707.04224.pdf|hit the arxiv last week]] (Paolo)
  - Any other business