Welcome to the Exposure Time Calculator. The ETC is a web-based application developed in Java 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)

ETC 18.0 uses pysynphot to derive these values for all the instruments.

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 Origions Spectro (COS)
Near Infrared Camera and Multi Object Spectrometer (NICMOS)
Space Telescope Imaging Spectrograph (STIS)
Wide Field Camera 3 (WFC3)

Since each instrument onboard Hubble is unique with its own image capturing modes, a separate ETC input web page must be 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.

Shortcuts

Pysynphot

ETC


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