A.3: Additional Available-but-Unsupported Options

There are a few additional available-but-unsupported capabilities that can be used (upon justification and approval) for certain applications:

  • Spatial scans, which are a supported mode for WFC3 observations (see WFC3 ISR 2012-08: Considerations for using Spatial Scans with WFC3), can also be used with the STIS CCD as an available-but-unsupported mode. For more information on the potential advantages of spatial scanning and instructions on its implementation, please refer to the dedicated section 12.12 Spatial Scans with the STIS CCD.
  • While the use of GO wavecals employing the default exposure times is supported, there are cases where longer exposure times may be needed. Some programs (e.g., where extremely precise wavelength zero points are required) or ones  using settings where the fading of the emission lines in the calibration lamps has been most severe (e.g., STIS ISR 2017-04) may benefit from somewhat longer wavecal exposures times.  Because the calibration lamps have limited lifetimes, the use of longer wavecal exposures requires adequate justification and approval.
  • POS TARGs (see Section 11.5) may be used to adjust the placement of targets behind the coronagraphic bars.
  • Some programs requiring very high photometric accuracy and reproducibility in first-order spectra obtained with the FUV and NUV MAMAs (e.g., in comparisons between data from multiple epochs) may benefit from disabling the default monthly positional offsets applied in executing such observations. Starting in Cycle 30, this previously restricted capability (using the MSMOFF mode) will become available-but-unsupported; users for whom this option may be beneficial should consult the Help Desk.
  • Due to lack of recent use and to significant uncertainties in its current sensitivity, use of the NUV PRISM will be considered as available-but-unsupported starting in Cycle 30.
  • Programs using G750L or G750M and need high signal-to-noise may ask for longer fringe flat exposure times.  Since the lamps have a limited lifetime, this is an available-but-unsupported mode (see Section 11.2.3).