1.1 New for Cycle 29

We have made the following updates to the WFC3 Instrument Handbook for this cycle:

  • We have provided updated plots of dark current vs date using darks with (Fig 5.8) and without (Fig 5.7) software correction for CTE losses (Section 5.4.8).

  • We have provided updated plots of hot pixel percentage vs date using darks with (Fig 5.13) and without (Fig 5.12) software correction for CTE losses (Section 5.4.9).

  • We have explained pixels categorized as hot or cold, stable or unstable, on the UVIS detector and plotted the percentage of pixels in these categories vs date (Fig 5.14) (Section 5.4.9).

  • We have created a new plot (Fig 5.16) showing how the EPER method complements stellar imaging measurements to reveal the decline in CTE over time for several illumination levels, and to reveal the relationship between CTE evolution and solar activity (Section 5.4.11).

  • We have explained pixels categorized as hot or cold, stable or unstable, on the WFC3/IR detector and plotted the percentage of pixels in these categories vs date (Fig 5.30) (Section 5.7.7).

  • We call attention to the Quicklook database, which displays information about instrument performance (Section 6.1, Section 7.1) and optical anomalies (Section 6.11.6, Section 7.9.7).
  • We have changed the recommended level of Flash needed in UVIS exposures with low background to bring the total background level to 20 e-/pixel instead of 12 e-/pixel (depending somewhat on trade-offs between S/N and CTE losses in different science programs), explaining why this increase is critical now that CTE losses are so much greater than in earlier cycles (Section 6.9.2).

  • We have presented a new set of plots (Fig 6.20) to show how substantially CTE losses have increased over time, especially for faint stellar images on low background, and how even flc images, created with pixel-based CTE correction software, have had increasingly limited ability to recover flux correctly (Section 6.9.3).

  • We are announcing modification of the IMPHTTAB for the UVIS detector to account for changes in inverse sensitivity ~ 0.1 - 0.2% per year according to filter over 10 years, with consequent corrections and improvements in the keyword PHOTFLAM, in the sensitivity ratio PHTRATIO in FLT/FLC data, and in the encircled energy (EE) correction (Section 6.10).
  • We are announcing the creation of dither patterns of up to 9 steps for WFC3/UVIS phase II proposals, designed to preserve sub-pixel sampling as much as possible over the face of the detector (Section 6.12.1, Appendix C Section C.2).
  • We have revised the discussion of Drift and Shift (DASH) observing strategy, with particular attention to aspects of planning that depend on gyroscope performance (Section 7.10.6).
  • We have presented new calibrations of the G280 grism (Section 8.2)
  • We have discussed the use of the hstaxe software to analyze grism exposures (Section 8.2, Section 8.5).
  • We have provided new references concerning the modeling and removal of background components from WFC3/IR grism exposures (Section 8.5).
  • We are introducing the Exoplanet Catalog ExoCat to help observers optimize target selection and prevent target duplications in spatial scans of exoplanets (Section 8.6).
  • We have provided overhead times for Small Angle Maneuvers for a greater range of offsets in Table 10.1 (Section 10.2).
  • We have discussed the relationship between synphot, stsynphot, and pysynphot, described the creation of new science datafile extensions related to the WCS, and described the hstaxe software that replaced the aXe software package for analysis of grism exposures in Appendix E (Section E.1).
  • We have added a summary of the WFC3 calibration plan for the upcoming cycle in Appendix E (Section E.14)