The Calibration Setup page allows a user to choose between user-defined and system-defined calibrators. It is STRONGLY recommended to choose the system-defined option; the observatory will ensure that suitable calibrators are used.
When user-defined calibration is specified, a table appears (Figure 5.8) in which the calibration sources can be added, deleted or edited. The initial list of calibrators describes the default calibration scheme for ALMA projects and appear in the approximate order in which they will be executed. There are three pointing observations and these are associated with the calibration that appears below them i.e. the first pointing is for the amplitude calibrator. Atmospheric calibrators (
) are not shown, but do comprise part of the default calibration scheme.
Two types of calibrator are available: fixed and dynamic. Fixed calibrators request a specific source whilst the dynamic variant consists of criteria (position, search radius, flux limits) that are used to choose a source from the ALMA calibrator database at the time that the SB is executed. Dynamic queries can be tested during Phase 1, but the database is likely to change between proposal submission and program execution.
The main use of user-defined calibration is probably to change some of the default dynamic queries to fixed calibrators. It is also possible to define additional calibrations and even to remove some of the defaults, but this is strongly discouraged. Doing so will change the time estimates for a project and must be justified in the Technical Justification. Simply choosing user-defined calibration will alert the Technical Assessor via the TA Flag Sheet and deleting or adding calibrations will trigger a validation warning.