Release Notes for ETC 27.1

New Features

Welcome to ETC 27.1. This version of the ETC implements the following improvements, notably:


  • The ETC evaluation date was updated to 2020-Apr-01 (MJD 58940).
  • The Y-axis units on the “Observed Target Spectrum” plot have been updated for clarity.


  • Updated the ACS/WFC dark rate from 0.01058 to 0.0124 counts/s/pix.


  • Nothing additional to report


  • Updated the STIS/CCD dark rate from [0.021, 0.025, 0.030] to [0.021, 0.026, 0.031] counts/s/pix (low, medium high).
  • The STIS Synphot throughput files were updated to give the same default evaluation MJD as ETC calculations.


  • Updated the WFC3/UVIS dark rate from [0.0025, 0.0025] to [0.00264, 0.00256] e-/s/pix (UVIS1, UVIS2).


  • The wording of various sections of the user’s guide has been improved for clarity.

Under the hood

  • The ETC is using pysynphot 0.9.12, which is obtainable from the Astroconda channel, running under Python 2.7.

Resolved Issues


  • The ETC 26.1 underestimated the S/N obtained with the new G140L/800 mode, and conversely, overestimated the time required to achieve a certain S/N. This was subsequently corrected in ETC 26.2, and we strongly recommend that users recalculate their results using the most recent version of the ETC.

Known Issues

Please see the News and Known Issues page for known issues with this release.


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