In a nutshell, Phase 3 denotes the process in which principal investigators of ESO observing programmes return their reduced data products to ESO for storage in the ESO archive and subsequent data publication to the scientific community. ESO’s policies governing Phase 3 are specific to the type of observing programme. Phase 3 is mandatory for ESO Public Surveys and for ESO Large Programmes since period 75. For other ESO programmes there is no obligation but PIs are invited to take advantage of the Phase 3.

To ensure the successful integration of External Data Products (EDPs) into the archive, ESO supports the users in carrying out the Phase 3 process by defining ESO/EDP data standards, by devising procedures and providing the infrastructure for the delivery of EDPs, and by supplying tools for the data preparation.

The description of the policies, the data standard and the procedure for the submission of reduced data products applicable to the ESO Phase 3 process given here is intended to provide the information for the preparation and successful completion of the ESO Phase 3 process. The target audience consists of the principal investigators and their collaborators who return reduced data products resulting from ESO observations for public release to the astronomical community through the ESO archive.

In March 2011, Phase 3 operations have started to support the validation, transfer and publication of the first data products from ESO public surveys. Other ESO observing programmes will be handled through the Phase 3 system as soon as the underlying data products standard and infrastructure have been extended to cover the respective instruments and data product types.