2.4 Use of Available-but-Unsupported Capabilities

The set of core instrumental modes/capabilities of STIS described in this Handbook that will be supported for Cycle 30 enables an enormous range of scientific applications. 

There are, however, additional "Available-but-Unsupported" capabilities (e.g., additional slits and data-taking formats) that are not described in this Handbook and that are not supported for Cycle 30.  If you find that your science cannot be performed with the supported modes and parameters described in this Handbook, you may wish to consider use of an unsupported mode, which may be approved for use upon consultation with a STIS Instrument Scientist.  A general description of STIS available-but-unsupported echelle, first-order grating, and NUV_PRISM capabilities is given in Appendix A.  Complete lists of the supported and available-but-unsupported combinations of aperture, optical element, wavelength, and detector, for each type of observation (ACQ, ACQ/PEAK, ACCUM, TIME-TAG) are given in the various subsections of section 8 in the Phase II Proposal Instructions.

The use of unsupported modes comes at a price, and they should be used only if the technical requirement and scientific justification are particularly compelling. Proposers should be aware of the following caveats regarding unsupported modes:

  • STScI adopts a policy of shared risk with the observer for the use of unsupported capabilities. Requests to repeat failed observations taken with unsupported capabilities will not be honored if the failure is related to the use of the unsupported capability.
  • User support from STScI for observation planning, as well as data reduction and analysis, for unsupported capabilities will be limited and provided at a low priority. Users taking data with unsupported capabilities should be prepared to shoulder the increased burden of the planning, calibration, reduction, and analysis.
  • While enabling "available-but-unsupported" modes in the Phase II APT makes all of these options available in APT, observers must remember that they are allowed to use only those particular "available-but-unsupported" capabilities for which they have been specifically granted permission.
  • Some of the options that are accessible as "available" in the APT software may nonetheless be prohibited for a variety of technical or policy reasons, and their presence in APT does not necessarily mean that permission will be granted to use them, regardless of any scientific justification that may be supplied. Observers should specifically note any restrictions on allowed observational modes that are listed in the Cycle 30 Call for Proposals.
  • Calibrations for unsupported capabilities will not be provided by STScI. Either users must determine that they can create calibration files from data in the HST Archive or they must obtain calibrations as part of their observations. The STScI pipeline will not calibrate data taken in unsupported modes but will deliver uncalibrated FITS files (or in some cases partially calibrated FITS files) to the observer and the HST Archive.

Cycle 30 Phase I proposals that include use of unsupported STIS capabilities must include the following:

  1. Justification of why the science cannot be done with a supported configuration;
  2. A request for any observing time needed to perform calibrations;
  3. Justification for the added risk of using an unsupported mode in terms of the scientific payback;
  4. Demonstration that the observers are able to bear the increased burden of calibration, reduction, and analysis of their data.

During the Phase II proposal submission process, STScI must also formally approve the use of an available-but-unsupported mode. This allows STScI to evaluate the request and ensures that no problems associated with the request have come to light since the submission of the Phase I proposal. We require the PI to summarize the above four points in a brief email message requesting approval for use of an available-but-unsupported mode.

The increased burden of calibrating data taken using available-but-unsupported modes also makes the use of such data for archival research significantly more difficult. As a result, requests for use of unsupported modes which do not adequately address the above four points, or which will result in only marginal improvements in the quality of the data obtained, may be denied by STScI, even if the request was properly included in the Phase I proposal.