The structure and step-by-step algorithms for the JWST calibration pipeline are documented along with the process that is used for deciding the pipeline algorithms as well as any updates.
The calibration pipeline consists of three stages. Each stage consists of many steps. Where practical, calibration pipeline stages and steps are shared across instruments and observing modes. For example, the near-infrared instruments use similar detectors, allowing similar calibration steps in the initial detector processing stage. In later stages of the calibration pipeline, significantly different steps are needed leading to an increasing divergence in the steps used to process the data (e.g., imaging versus spectroscopy).
The algorithms for use in the calibration pipeline are the result of input from the instrument teams and a few mode specific working groups. These inputs are reviewed and discussed in the JWST Calibration Working Group (CalWG) to ensure that the best possible algorithms. The overall goal of the CalWG is to adopt the best possible algorithms based on experience from previous missions and observatories (Hubble, Spitzer, ground-based) and experience from the ground-testing of the JWST instruments. The membership of the JWST CalWG is composed of all members of the instrument and community that are interested in contributing to the effort of defining the best possible algorithms for JWST. After acceptance by the JWST Cal WG, they are implemented in code by the Science Software Branch with the JWST Data Management Systems WG (DMSWG) ensuring that the requested algorithms are implemented through extensive testing of the as-built pipeline.
The goal of the baseline version of the calibration pipeline is to produce data reduction for all instruments and observing modes prior to launch. This focused the efforts of the JWST CalWG to find algorithms for each step in the pipeline that will produce good quality science at launch while at the same time requiring reasonable computational resources.
The optimal version of the calibration pipeline will produce the best quality data reductions. The optimal algorithms for each step start with the baseline and are updated if and when there is a better algorithm proposed. As a result, the optimal version of the pipeline is a never ending goal only approached asymptotically. In other words, the "optimal" name describes the continuing development of the pipeline through the JWST mission.
Published July 11, 2017