Release Notes for ETC 34.2

New Features

Welcome to ETC 34.2, released in May 2026.

34.2 includes data updates, improved COS brightest pixel values, some CALSPEC SED updates, and some small bugfixes.

General

• The ETC evaluation date remains at 2027-Apr-01 (MJD 61496).

• CALSPEC model updates for Vega, GD50, LDS749B, P330E, WD1657+343, WD0308-565, and WD1057+719. (HETC-1014)

• Added text suggesting Gaia normalization be performed in the Vega magnitude system. (HETC-1037)

ACS

• ACS/SBC throughputs were updated to reflect the changing sensitivity of the detector, as measured on 2026-Mar-15. (HETC-1010, INSACS-158, RFD-2223)

• The ACS/WFC dark rate has been changed from 0.0176 to 0.0175 cts/s/pix. (HETC-1010)

COS

• COS/FUV G130M and G160M throughputs were updated based on the COS lifetime position usage plan for Cycle 34. (HETC-1011, RFD-2230)

• The COS/FUV dark rates for spectroscopic modes have changed for [FUVA, FUVB] from [3.15e-6, 3.81e-6] to [2.61e-6, 2.66e-6] cts/s/pix. (HETC-1011)

• The COS/FUV dark rates for target acquisition modes have changed for [FUVA, FUVB] from [6.00e-6, 6.45e-6] to [4.60e-6, 4.57e-6] cts/s/pix. (HETC-1011)

• The COS/NUV dark rate has changed from 1.17e-3 to 1.04e-3. (HETC-1011).

• The COS/FUV enclosed energy tables were updated to improve the 1-pixel full height used to calculate brightest pixel values. New cenwave- and wavelength-dependent updates were based on current profile tables. (HETC-1011)

STIS

• The CCD dark rates for [low, medium, high] were updated from [0.029, 0.034, 0.041] to [0.028, 0.035, 0.042] cts/s/pix, respectively. (HETC-1012)

• The NUV dark rate was changed from 0.00071 to 0.00076 cts/s/pix. (HETC-1012)

WFC3

• No change (HETC-1013)

Documentation

• Updated dark rates and other scalars in the User’s Guide. (HETC-1028)

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.