2023-03-XX: lbti-*wfs: ncpa threshold phase 1: apply NCPA only if the difference is greater than a threshold applied in NCPA FITS files

  • Software versions used:
    • sxadsec and/or dxadsec: stable
    • lbti-sxwfs and/or lbti-dxwfs: test.202303XX.ncpa-threshold-phase1
  • Software versions after test:
    • sxadsec and/or dxadsec: stable
    • lbti-sxwfs and/or lbti-dxwfs: stable
  • SW: Brandon


This test is for phase "1.5" of the proposed NCPA changes. I say "1.5" because this change also updates the minimum interval of phase 2. As a reminder, here are the phases we discussed in the AOSW meeting:
  1. Phase 1: Add threshold for NCPA.
  2. Phase 2:
    1. Do not update if the time elapsed since the last update is less than the minimum interval between updates (10s).
    2. Add a safety check for the amplitudes requested.
  3. Elevation-dependent calculation for iLocater.
# subsystem(s) pull request link description / reason for upgrade
1 adsec + wfs WfsArbitrator: NCPA threshold phase 1
Interprets the first row of the NCPA calibration files as a threshold. If the difference between the current NCPA offsets and the requested NCPA offsets is less than the threshold or if the amount of time since the previous successful NCPA update was less than wfsarb.conf's "ncpaTrackInterval" setting, the NCPA won't be applied.


  1. The daytime test checklist is here: https://docs.google.com/spreadsheets/d/1jjr8oyWWlJs5v0xp1_9LHLynhbMaVjfZDHVC2gEC7sQ/edit?usp=sharing
    The test is to verify that turning on and off NCPA works, that sub-threshold requests are ignored, and that the minimum interval is used. The test can be done using LBTI or LUCI on either side, but since the request is highest priority for LBTI, it makes sense to do the test with LBTI.
-- BrandonMechtley - 28 Feb 2023
Topic revision: r2 - 01 Mar 2023, BrandonMechtley
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