Release Notes for ETC 25.2

Welcome to the Exposure Time Calculator (ETC). The ETC is a web-based application developed in python that assists Hubble astronomers and engineers in preparing Phase I and Phase II observing proposals for submission to the Space Telescope Science Institute (STScI). The ETC’s sole purpose is to calculate the following:

  • Signal-To-Noise (SNR) Ratio (for a given Exposure Time)
  • Exposure Time (given a desired SNR Ratio)

The ETC calculates SNR or Exposure Time for a simulated astronomical observation using one of Hubble’s primary instruments:

  • Advanced Camera for Surveys (ACS)
  • Cosmic Origins Spectrograph (COS)
  • Space Telescope Imaging Spectrograph (STIS)
  • Wide Field Camera 3 (WFC3)

Since each instrument on board Hubble is unique with its own image capturing modes, a separate ETC input web page has been created for every combination of instrument and science image modality. A single server shared by all of the instruments, however, handles all the SNR calculations and output pages. This common server uses pysynphot as its synthetic photometry calculating engine.


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Release Notes for ETC 25.2

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