Release Notes for ETC 34.1.1

New Features

Welcome to ETC 34.1.1, released in December 2025.

34.1 includes data updates, ACS/SBC empirical backgrounds, Gaia normalization, a new supernova template, and some small bugfixes.

34.1.1 fixes the ACS/SBC empirical background scaling levels.

General

• The ETC evaluation date was updated to 2027-Apr-01 (MJD 61496).

• Gaia bandpasses added to SED normalization options. (HETC-993, REDCAT-201, RFD-2084)

• Type Ia Supernova template added. (HETC-891, REDCAT-180)

ACS

• 34.1.1: The 34.1 empirical background levels were increased by a factor of 1.62. (HETC-1006)

• ACS/SBC imaging has a new empirical background option that can be used instead of the ETC estimates for zodiacal light, earth shine, air glow, and dark current. (HETC-992)

• The ACS/WFC dark rate has been changed from 0.0169 to 0.0176 cts/s/pix. (HETC-966)

COS

• COS/FUV throughputs were updated based on new HV Dependent Sensitivity. (HETC-967, RFD-2115)

• The COS/FUV dark rates for spectroscopic modes have changed for [FUVA, FUVB] from [3.93e-6, 4.91e-6] to [3.15e-6, 3.81e-6] cts/s/pix. (HETC-967)

• The COS/FUV dark rates for target acquisition modes have changed for [FUVA, FUVB] from [7.51e-6, 8.18e-6] to [6.00e-6, 6.45e-6] cts/s/pix. (HETC-967)

• A warning was added to some COS/FUV G130M cenwaves in the spectroscopic acquisition ETC for modes not supported in the COS2025 policy. (HETC-949)

STIS

• The CCD dark rates for [low, medium, high] were updated from [0.028, 0.033, 0.040] to [0.029, 0.034, 0.041] cts/s/pix, respectively. (HETC-968)

• The NUV dark rate was changed from 0.00094 to 0.00071 cts/s/pix. (HETC-968)

WFC3

• The WFC3/UVIS dark rates for [UVIS1, UVIS2] were updated from [0.00213, 0.00222] to [0.00285, 0.00301] ADU/s/pix. (HETC-969)

• WFC3/IR imaging filter throughputs were updated with time-dependent sensitivity loss. (RFD-2075)

Documentation

• Updated dark rates and other scalars in the User’s Guide. (HETC-983)

Under the Hood

• No change

Resolved Issues

• No change

Known Issues

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