Discussion items

TSO Timing PrecisionKevin
  • ISIM clock is not precise enough for TSO
  • Use FPE clock for relative time and S/C clock for reference point
    • Frequency of FPE clock has a slight temperature dependence (10 ppm variation in flux over 25 K variation in temperature)
    • John Stansberry has had success getting CV3 data to check temperature stability of FPE
    • Will discuss results next month
  • Duration of "second" isn't always constant during an observation
    • Offset may be applied during contact to correct drift in s/c clock
  • Use engineering telemetry data to determine timing offset correction
    • Current plan is to flag exposures in which an offset occurs
    • Users will need to access engineering data to determine which integrations were affected
    • Will need to write technical memo (TM) describing spacecraft clock correction, engineering mnemonic SCTA_OFFSET, and how to access engineering data to see where within the exposure the correction was applied
  • Working on generating simulated data for TSO MIRI Direct imaging Full Array mode, not high priority
  • Still reviewing results of passing simulated data through pipeline

Target fluence recommendations
    • Recommend ~35K ADU
    • Mean bias = 11.6k ADU
    • Mean soft saturation = 50.5 ADU above bias (range is 43k-59k)
    • Recommend ~35k ADU??? (~75% of saturation)

Data Segmentation
  • Files need to be segmented into chunks if they are too large
  • Baseline version of segmentation code works, but doesn't optimize for different values of NGROUPS
  • In some cases, the choice of 2GB per segment results in large level-2a products (e.g. 6 GB in size). The 2GB segment size is fine for a single level-1b FITS file.  In the case that NGROUPS=3 though, there's very little "compression" due to ramp fitting in the level-2a products, and because the level-2a products inflate the original raw data from int16 to float32, as well as add several more float32 data arrays of the same size (ERR, DQ, ...), resulting in the level-2a products that were ~6 GB in size.
    • Decision: Use size_level1b = size_level2a * ngroups / 10.  Pick what the size_level2a we want, and then L1b and segment size will follow from there via the equation
    • Work hasn't started on new version
  • Will need to briefly discuss file segments in JDox TSO strategy pages and link to more detailed discussion

Action items