Overview of the AP pipeline

lsst.ap.pipe is a data processing pipeline for Prompt Data Products. It is a Command-Line Task which operates on ingested raw data in a Butler repository. It also requires appropriate calibration products and templates. As it runs, ApPipeTask generates calibrated exposures, difference images, difference image source catalogs, and a source association database.

The initial motivation for lsst.ap.pipe, information about one of the original test datasets, and an outdated tutorial are available in DMTN-039.

The AP Pipeline calls three main tasks and their associated subtasks:

  1. ProcessCcdTask, which in turn calls lsst.ip.isr.IsrTask, lsst.pipe.tasks.CharacterizeImageTask, and lsst.pipe.tasks.CalibrateTask to perform image reduction as well as photometric and astrometric calibration;
  2. ImageDifferenceTask, which uses many utilities from lsst.ip.diffim; and
  3. AssociationTask, which makes a catalog of Difference Image Analysis (DIA) Objects from the DIASources created during image differencing.

In practice, lsst.ap.pipe is often discussed in the context of lsst.ap.verify. The former is responsible for running the AP Pipeline. The latter uses lsst.ap.pipe to verify the output.

ap_pipe is entirely written in Python. Key contents include: