3.5 OTFR - On The Fly Reprocessing
In section 3.1, we learned how "on the fly reprocessing" (OTFR) solves the problem of archiving large ACS datasets. Several other important OTFR features become apparent at this stage.
The most current ACS reference files are used by CALACS each time OTFR is run. Since reference files such as CCD biases and darks are frequently updated, OTFR may use different reference files depending on the date of reprocessing. Previously, the archived data from DADS had to be re-calibrated by manually running the calibration software on the user's home workstation with the updated reference files. OTFR replaces this step by automatically re-calibrating with the most current reference data available. The user simply waits until the contemporaneous reference files are in place and requests the data via StarView or the HST web-based archive request form. The image header keywords are then updated with the names of the reference files used during that specific OTFR run. The PROCTIME keyword reflects the pipeline processing date and time in MJD.
OTFR allows the user to avoid downloading archived data which is outdated because of software changes made for bug fixes, improved algorithms, new capabilities, or header keyword changes. An archive request for calibrated data will result in OTFR reprocessing and distributing the corrected data using the latest software versions available.
Currently OTFR will distribute all files associated with an ACS observation, including both uncalibrated and calibrated files. Future versions will enable users to select certain parts of the dataset, for example only the final calibrated image. Future versions of OTFR could also enable users to set calibration parameters for a particular OTFR run. Until then, OTFR will process with default values. Of course, the option of re-calibrating aside from OTFR still exists.
