Date

Slides & Recording

Attendees

Agenda 

  • News & Announcements
  • TSO upcoming observations + TTRB highlights (Carter)
  • SOSS Multistripe Update (Carter)
  • SOSS Background Subtraction (Baines)
  • FGS Timestamps (Espinoza)
  • DHS Status Updates (Stansberry)  
  • Closing remarks

Discussion items

TimeItemWhoNotes
2 minNews & AnnouncementsAll


  • Nestor Espinozashares that the HSTMO approved 4 orbits to obtain contemporaneous WFC3 observations of WASP-18b with the DHS observations for cross-calibration of systematics 


8 min  TSO upcoming observations + TTRB highlightsCarter
  • A few KELT-8 observations were executed and are scheduled in the coming days
  • No TTRBs to report!
5 min SOSS Multistripe UpdateCarter


  • Aarynn Carter shares that SOSS is fully supporting MULTISTRIPE in Cycle 5 for targets down to J mag of 3.5 (details/info in JDox)
    • Another parameter for number of exposures per observation will be added in the coming weeks
    • Aarynn Carterwill be giving a JWebbinar on MULTISTRIPE on Sept 4th 
  • Nestor Espinoza mentions that MULTISTRIPE will be also be useful beyond transiting exoplanets and BDs, like folks interested in Cepheids grinning face 
  • Everett Schlawin asks what the testing status is
    • Aarynn Carter mentions that for now the plans are to do standard wavelength flux cal programs 
  • Next up: Nestor Espinoza mentions that we should start thinking about how NIRSpec (and PRISM in particular) can implement MULTISTRIPE - need to notify/convince the managers 
    • Munazza Alam will ping Jeff about getting the ball rolling on this 


15 min SOSS Background SubtractionBaines


  • Tyler Baines shares work on improving SOSS data reduction background subtraction since current implementation uses a generic model background template which is scaled to match an individual exposure - but this is mis-scaled for some observations!
  • Simulations of the zodiacal background take a seed image of the trace and shift it across the FOV of the pick off mirrors, summing all flux for permitted target positions
  • cal program to acquire 10 exposures per sky position with data acquired above, below, and along ecliptic plane (+ Cycle 4 obs coming soon)
    • derived empirical background template by combining pixel masks 
    • applied to all obs to derive a library of backgrounds, which shows how the bkg changes as a function of ecliptic latitude 
      • brighter along ecliptic and fainter as we move away from it 
  • zodiacal light drives the modulation of the SOSS background, with offsets and amplitude modulations at different sky positions  
    • dust properties become more relevant >3 microns  and could explain the modulation that we see 
  • the background also changes across seasons
    • used cal observations of BD + 60 as a proxy of these seasonal variations, even at high ecliptic latitudes
    • background varies as much as ~40% (~1 DN/s) over the course of the year  
  • PID 2113 to benchmark background exposures alongside science observations 
    • ~17% of pixels are background 
    • contemporaneous background-subtract shows bias of ~0.46 counts due to the wings of the traces in the orders 
    • applied empirical background to compare no scaling, global 1-component scaling, and 2-component split scaling 
      • no scaling does not do a good job 
      • 1-component does better, but over-subtracts in some cases
      • 2-component does even better capturing the background variations
  • split 2-component background scaling method implemented in JWST pipeline! 
  • Everett Schlawin asks if you can do a scaling by all of the orders vs the components - not at the moment, the toy model currently used is for illustrative purposes of the background
  • Aarynn Carter shows that applying this background subtraction method pulls out water features for a test data set compared to not applying the background subtraction! 


10 minFGS TimestampsEspinoza


  • Nestor Espinoza mentions that folks are using the FGS data to compare their data for detrending, handling tilt events, etc. - but the cadence and time stamps do not match the observations 
    • telemetry data is time stamped directly from the ICDH (which assigns time stamps on board), but on the ground it gets corrected by Julian date, etc 
      • these corrections are described in Jira ticket JSDP-2267 (see packet_time.py code in this ticket)
    • certain groups are time stamped with these corrections, but FGS data does not have this processing
  • Nestor Espinoza bumped some help desk tickets to the FGS folks so that they can think about processing these time stamp corrections for the FGS data as well 
  • Aarynn Carter and Munazza Alam discussed whether this is applied for all instruments such that all instruments have consistent time stamps with each other
    • Nestor Espinoza notes that all the instruments should be consistent with each other for the science  data, but the ground time stamp corrections are only applied to all science data (not telemetry) 
  • Everett Schlawin asks if Nestor recalls how the tilt event seen in the first TSO data set was corrected - it was a fudge factor to account for the timing offset


5 minDHS UpdatesStansberry


  • John Stansberrymentions that there isn't much to update, but the Arizona lab can reproduce the anomaly warm and they will do the tests cold again 
  • some analysis is also underway to look into ASIC micro dumps, but no real progress in figuring root cause based on what is going on with the ASICs (it was not the ASIC sync that caused this)
    • NIRISS would also be subject to this issue even though there is no ASIC sync for SOSS
  • flight ops and testing folks would like to have a larger discussion with other folks from the TSO CT about the current status 
    • and sharing the status with the community as well 
  • Goddard has the leftover FPE from Lockheed, but they need to find that to reproduce the most similar flight-like conditions
    • but Arizona already has this setup working, so what is the benefit of having two set ups to help with this?
    • need to figure out the best way to add resources in a useful way 
  • some urgency to describe accurately and in detail the issues with MULTISTRIPE for NIRCam in the Sept 4th JWebbinar 


5 minClosing remarks All 


  • Hannah Diamond-Lowe shares that the MIRI subarrays are uploaded to SIAF and won't be available for Cycle 5 - but are on their way to being available 


Action items

  • Munazza Alam will ping Jeff about getting the ball rolling on implementing MULTISTRIPE for NIRSpec