The calibration and cross-calibration of the Herschel instruments is the responsibility of the observatory, in particular of the ICCs and the HSC. The pointing calibration is the responsibility of the HSC and the MOC. Therefore, the preparation and scheduling of calibration observations has been an exclusive duty of these groups. The calibration data required for the reduction and analysis of the Herschel observations is provided to the astronomer in the form of products in the Herschel Science Archive, and is integrated in the Data Processing software.

Calibration and engineering observations were the main components of the schedule during the Commissioning and Performance Verification phases. Their aim was to achieve the necessary understanding of the instruments and spacecraft, and attain the required calibration and pointing accuracies to ensure a proper execution and data reduction of the science observations during the Science Demonstration and Routine phases. Over the duration of the routine phase, up to 15% of the available observatory time has been used for calibration, with the amount of calibration time decreasing towards the end of the mission, as instrument characterisation was completed and only routine trend analysis and health checks became essential. Calibration observations may be based on non-AOT observing modes defined by the instrument specialists at the ICCs and HSC, but in general they have been defined using the AOTs available to the community for science observations.

Calibration observations are in principle public and have been made available throughout the mission to PIs, if justified, sometimes by "buying" the observation against time awarded by HOTAC, which transferred it to the PI along with the corresponding proprietary rights, often "free of charge", by making the observation public and available to all users. However, if a calibration observation is a duplicate of a scientific observation (see the "Herschel Space Observatory Call for Proposals: Policies and Procedures" document for a definition of "duplication"), the corresponding proprietary rights have been applied.

Note

Neither calibration nor engineering observations appeared in the listing of observations that were scheduled for observation and delivered to MOC, but not yet executed (http://herschel.esac.esa.int/observing/ScheduleReport.html), or the observing log of executed observations (http://herschel.esac.esa.int/observing/LogReport.html). The observing log constitutes the official record of executed science observations during the Herschel mission.