Release Notes for ETC 31.2

New Features

Welcome to ETC 31.2, released in August 2023.

This version includes a few small bugfixes along with data updates.


  • The ETC evaluation date remains at 2024-Apr-01 (MJD 60401).
  • The versions of some HST standard star spectra (CALSPEC) were incremented. (HETC-689)


  • No change


  • The COS/NUV dark rate updated from 1.03e-3 cts/s/pix to 1.25e-3 cts/s/pix. (HETC-686)
  • The COS/FUV dark rates for spectroscopic modes have changed for [FUVA, FUVB] from [2.20e-6, 2.75e-6] to [3.83e-6, 4.93e-6] cts/s/pix. (HETC-686)
  • The COS/FUV dark rates for target acquisition modes have changed for [FUVA, FUVB] from [3.56e-6, 4.73e-6] to [7.10e-6, 7.88e-6] cts/s/pix. (HETC-686)
  • The pull-down display string for COS Spectroscopy Target Acquisition NUV/G225M/c2373 was updated with the correct wavelength ranges. (HETC-683)


  • STIS NUV throughputs (except PRISM) were updated based on recent time-dependent sensitivity monitoring data from program 16960. (HETC-687, RFD-1509)
  • The CCD dark rate for [low, medium, high] changed from [0.025, 0.030, 0.036] to [0.026, 0.031, 0.037] cts/s/pix. (HETC-687)
  • The NUV dark rate updated from 0.0022 cts/s/pix to 0.0020 cts/s/pix. (HETC-687)


  • The WFC3/UVIS postflash limit was increased from 25 e- to 40 e-. (HETC-626)


  • Updated dark rates and other scalars in the User’s Guide. (HETC-702)
  • Updated postflash references.

Under the Hood

  • Updated internal location of Phoenix model files. (HETC-707)

Resolved Issues

  • No change

Known Issues

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


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