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Date

Attendees

  • Kevin Stevenson

  • Stephan Birkman

  • John Stansberry
  • Bryan Hilbert
  • Nikole Lewis
  • Sarah Kendrew
  • Jonathan Fraine
  • Online attendees

Acronyms

  • TA = target acquisition
  • TSO = time-series observations
  • FoV = field of view
  • ETC = JWST exposure time calculator

Discussion items

TimeItemWhoNotes
General UpdateKevin
  • See slides titled ""
  • TA was recently brought up as a concern for TSOs of bright targets and how STScI would handle proposals/targets for which TA was not feasible
  • WG performed study of TA limits for all four instruments
    • NIRISS: no concerns, can always perform TA on science target
    • NIRCam: can achieve 0.1 pixel pointing accuracy with 4 partially and 1 fully saturated pixels (K = 6.1), brighter objects may need to use offset TA or saturate additional pixels with a decrease in pointing accuracy (~1 pixel)
    • NIRSpec: most objects will need to use offset TA, but brightness range is 11 < K < 25 therefore finding a suitable offset target should not be an issue
    • MIRI LRS: no concerns with LRS mode, can always perform TA on science target
    • MIRI Photometry: no TA for MIRI photometry, blind pointing accuracy (4 pixels at 1 sigma) is well within FoV for smallest subarray (SUB64)
  • Conclusion from TA study is that all science targets should have a viable means to perform TA
  • Potential improvements for Cycle 2
    • Narrow filter for NIRCam, fewer groups for NIRSpec, improved TA on saturated targets (software), micro-shutter assembly TA for NIRSpec
  • Other highlights include...
    • MIRI TSO photometry enabled for Cycle 1, includes full array and all subarray modes
    • Developed strategy to provide timestamps for each integration since time is recorded once every science (full frame) image, will create FITS extension with BJD_TDB times
    • Finalized "chunking" strategy for large datasets, exposures will be evenly divided into segments of <= 2 GB each; will enable faster processing of data and easier sharing on MAST
  • Everyone should update their local version of PandExo
 NIRCam TA with saturated pixelsBryan
  • See slides titled ""

ETC vs PandExoJonathan
  • See slides titled ""
  • ETC and PandExo produce consistent results (SNR) when the # of integrations is 1
  • ETC produces a significantly lower SNR (compared to PandExo) when the # of integrations is large
  • The is because the ETC includes the flat field uncertainty for every integration, which is correct for non-TSO data, whereas TSOs are a relative measurement that don't depend on a precise flat fielding, so long as the pointing jitter is small
  • ETC and PandExo do agree when we use the ETC SNR for 1 integration and then bin down assuming "root N" statistics
  • CONCLUSION: We should encourage people to use PandExo for their TSO planning

APTSarah
  • See slides titled ""
  • APT has gone through a series of updates over the past few months
  • Ran out of time to discuss JDox

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