Online: Karl, Shaul, Maurizio, Brendan

Agenda:
  * Upcoming workshop May 1-3; morning of May 3 will include Systematics section, afternoon of May 3 will be a systematics face to face
  * Maurizio: updates on gain stability:
      * Toast Bug: sudden jumps in pointing timeline 
      * While Andrea et al try to solve toast bugs, Maurizio is adapting a different sim code just to get an estimate of the dipole calibration.  Might be enough.
      * bug in the toast bug report system, Andrea and Ted K are aware of the bug, but no progress in ~ 1month [[https://github.com/hpc4cmb/toast/issues/224|See here for github discussion.]]
      * Andrea Z and Maurizio to meet in person next week: this is on the agenda for their meeting.
      * Another workaround: perhaps if this bug was introduced by a recent commit, then just revert toast version to non-buggy version.. maybe going back to the CORE version.
      * Maurizio to also check against CORE pointing.
      * Or possibly even just some brute force scripting to correct the problem.
  * Karl: GRASP
      * Plots prepped for TeamX, {{::grasp_results_20180318_karl.pdf| GRASP slides (Karl)}}
      * Basically ready with a 4pi sidelobe beam: Karl to produce a visualization
        * See plots below.  The first 2, with 2 circles per plot, are projected such that the forward 2*pi of the beam is shown in the left-hand plot, theta = 0 at the center, and the right hand plot shows the backward 2*pi, theta = 180 at the center.  The second 2 plots are the same simulation in a different projection.  Note on coordinates: co-pol is the E-field in the xz plane, cross-pol is the E-field in the yz plane.  Plots labeled pol X are using a beam from a feedhorn linearly polarized in the xz plane. Those labeled pol Y are from a feedhorn linearly polarized in the yz plane.
        *  {{:systematicswg:telecons:2018-04-04:polx_corrected_4pi.png?direct&100|Pol X}}  {{:systematicswg:telecons:2018-04-04:poly_corrected_4pi.png?direct&100|Pol Y}}  {{:systematicswg:telecons:2018-04-04:polx_corrected_4pi_flat_projection.png?direct&100|Pol X}}  {{:systematicswg:telecons:2018-04-04:poly_corrected_4pi_flat_projection.png?direct&100|Pol Y}} 
      * Brendan to ping Julian and Jacques about various code availability / sim plans for calculating pickup
  * Eric: beam angle
      * What is the noise at low ell?  he can assume white noise based on the instrumental sensitivity
      * Table of sims specify knee frequency in time domain, but sims need to be run
      * Angle errors: assumptions can be made that around 0.2 degrees 
      * What can you do if you don't try to null EB correlations?  How big a problem is it.
      * Check [[https://arxiv.org/abs/0912.3532|Yadav et al]]: they argue that S/N of EB correlation from a systematic will always be much larger than S/N on contamination in BB.
      *