On-The-Fly Reprocessing

STIS has moved from the On-the-Fly Calibration (OTFC) processing system to the new On-the-Fly Reprocessing (OTFR) system.

What's the Difference?

OTFC repairs data headers and updates reference files and keyword values in existing uncalibrated files, then recalibrates the data. OTFR makes new uncalibrated FITS files, then recalibrates them. Data are reprocessed from an early telemetry product called a "pod" file. With OTFR, raw data headers are re-built from these pod files, enabling many changes and fixes to be done at this early step, which were impossible with OTFC.

Reasons for the change

Easier maintenance of the processing system. Current implementation requires development and maintenance of separate OTFC and pre-archive pipelines. With OTFR there will be one version of pipeline, and one header format produced. OTFR also allows for the correction of non-keyword problems, such as fixes to STIS time-tag data format.

How will this affect my data? What will I see that's different?

You will continue to get the best calibrated data available, using the most up to date, best reference files, with the addition of improvements to the headers and data formats. You will be given a new trailer file, consisting of the current reprocessing history. This replaces the trailer files you received with OTFC where new processing pre-pending the original processing.

Retrieving your Data through OTFR

The added processing time for OTFR is negligible, and so retrieval times should not be affected for any Archival request. You will, however see a new Reference File Retrieval screen for STIS in StarView. There will no longer be a column for Used and Best reference files, since you will by default receive the best reference files, and Used becomes meaningless under the OTFR system.

Also in StarView, on the Retrieval Configurations Options screen, please note that both the Used and Best Reference File buttons remain. This option will remain for the time being, but is not really useful for STIS retrievals. After "final" versions of the heritage data have been re-archived, this option will be dropped. Until such time, we recommend that you always choose the "Best" option from this screen when requesting STIS data.

On the same Retrieval Configurations Options screen you will see that your options for retrieving only Uncalibrated or only Calibrated has disappeared. Under the current scheme, and for the next several months, you will receive both Uncalibrated and Calibrated data with every request. The expectation is that, once the DADS software is upgraded, users will again be able to select whether to receive calibrated data.

Finally, when you make a request, you will temporarily still see an auto-reply message referring to OTFC, but you will receive data processed through OTFR.