Welcome to the Exposure Time Calculator (ETC)

ETC 19.1 Bugs and Special Notices

The Following Pages are for ETC 18 Restricted Version

Bugs and Special Notices for ETC 18.2 (restricted version)

Release notes for ETC 18 (Restricted Version)

ETC Cycle 18 User Guide

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:

1. Signal-To-Noise (SNR) Ratio (for a given Exposure Time)

2. 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)

• Near Infrared Camera and Multi Object Spectrometer (NICMOS)

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.