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Space Telescope Imaging Spectrograph
Update on STIS Close-out Calibration (January 2007)

After the STIS failure on 2004-Aug-03, the STIS team put together a close-out plan for STIS re-calibration support.

The majority of the calibrations that were detailed in this plan and which affect the standard pipeline calibration of STIS data have been completed, and a re-calibration of all existing STIS data is well underway. When finished, this re-calibration will allow uniformly calibrated STIS data to be obtained from the HST archive without the need to re-create and re-calibrate the data files via the HST archive's OTFR (On-The-Fly-Recalibration) procedure each time they are requested. This should dramatically improve delivery times and render STIS data readily usable by the Virtual Observatory and related projects. As of 2007-Jan-30, 76,450 STIS datasets, or about 60% of the total, have been re-processed and re-archived.

While these re-processed raw and calibrated data files are not yet directly accessible to the user, apart from a few exceptions detailed below, the calibration enhancements that have been done are already available and are automatically applied whenever data is requested via OTFR through the current archive interface.

Currently available pipeline calibration enhancements include:


Pending enhancements include:

In addition to these improvements to the raw and calibrated data files, a few new post-analysis tasks are now available in the STIS package of the STSDAS distribution.


Remaining close-out items:

Work on the documentation describing many of the above items is ongoing, and several new instrument science reports (ISRs) should appear over the next few months. Many of the archive enhancements described in the original close-out plans, such as better previews and PSF libraries, will also be worked on over the next year.

The schedule for a few of the originally planned enhancements is less certain and is dependant on internal resource assignments. We still hope to make available a spectroscopic version of MultiDrizzle, which would enhance the combination of spectra that have been dithered in the cross-dispersion direction.

In the future, we also hope to take advantage of two improvements in STIS wavelength calibration that are currently being developed by the Space Telescope-European Coordinating Facility (ST-ECF):

  1. The ST-ECF has made new line-lamp measurements that have significantly improved the accuracy of the wavelengths for the lines of Platinum, Chromium, and Neon used in the STIS lamps. The far UV part of this line list (< 1700 A; Sansonetti et al., 2004, ApJS, 153, 555) has been published, and we have verified that the wavelength calibration of the first-order far-UV modes as currently implemented in the CALSTIS pipeline is not affected by the new line wavelengths to within the uncertainties quoted in the STIS Instrument Handbook. Once the near-UV part of the new Pt/Cr-Ne line list has been made available, we plan to evaluate the need for a revised wavelength calibration for the near-UV first-order modes.

  2. The ST-ECF is also developing a physical model of the wavelength solution for the high-resolution echelle modes that should be more accurate than the currently advertised dispersion solution uncertainties. When ready, we plan to make their software compatible within the CALSTIS structure and turn it into a post-observation task within STSDAS.


STIS Repair?

It should also be noted that the current plan for SM4, the next servicing mission to HST, includes time for an attempt to repair STIS. Some details of NASA's plan for a possible STIS repair can be found at
http://sm4.gsfc.nasa.gov/technology/instruments.php#stis

Completion of a final summary document, giving an overview of the impact of STIS, may be deferred until it is clear whether or not STIS will indeed be revived.