Space Telescope Imaging Spectrograph
ETC 18.0 Known Issues and Features

ETC 18.0 (formerly 18.1) was released on 10/24/2009.

The following changes were made:

• The CALSPEC files that ETC uses were updated to the preferred spectra. The current list of HST Calibration Spectra used by the ETC was updated with the preferred set as listed in the CALSPEC website
• Dark Current and Read Noise values were updated The Dark current and read noise changed after the repair of STIS. The new values are as follows:
  

  STIS CCD:

  Read noise:
  Gain = 1 5.6 e-
  Gain = 4 8.3 e- (~2.05DN)

  Dark current: 0.015 e-/pixel/s

  STIS NUV MAMA:

  Dark current: 0.005 counts/pixel/s

  STIS FUV MAMA:

  Dark current: 0.00015 counts/pixel/s

• Added GALEX passband normalization option GALEX passbands were added to the normalization menu for STIS. These filter choices are:

  GALEX FUV (1350 - 1750 Å)

  GALEX NUV (1750 - 2800 Å)

  which are normalized to AB magnitudes.
• A separate report is now given for global count rates and total count rates

  For all STIS ETCs, a separate sub-section was added to the detailed information output section with the following format:

  --------------------------------------------------
  Global Count Rates
  Source only             xxxx       xxxxx
  Background             xxxx       xxxxx
  --------------------------------------------------
  

  where the x's mark the place where the numbers will be. The left set of numbers gives the "count rates", integrated over the entire detector, due to just the source and just the background, and the right set gives the total counts in the exposure from the source or background (i.e., the first column times the exposure time).

  For extended sources in the STIS Imaging ETC and STIS ACQ ETC the following subsection was also added:

  --------------------------------------------------
  Background per unit area
  Sky Background (arcsec^-2)       xxx       xxxxx
  Dark Current (arcsec^-2)           xxx       xxxxx
  --------------------------------------------------
  

  where the left column of numbers gives the rate per second per square arcsec and the right column of numbers gives the total over the exposure.

  In the case of the STIS imaging and ACQ ETCs, the new output subsections described above replaced the following sub-section:

  --------------------------------------------------
  Count rate
  Source (infinitely large region)      36,175.21
  Sky Background (arcsec^-2)        34.51
  --------------------------------------------------
  
• ETC now uses PySYNPHOT