Next: HST Data Flow with On-The-Fly Reprocessing . ... While OTFC has performed well, a number of concerns about maintenance and flexibility have resulted in the evolution towards an On-The-Fly Re-Processing (OTFR) System. ... The pre-archive pipeline software is already implemented using OPUS, so it was straightforward to add OPUS pipeline stages to perform OTFR. ... The use of on-the-fly re-processing does have implications for the state of the archive catalog meta-data. ...