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Expected Source Properties

Once the source position and velocity information has been completed, details of the source brightness, polarization (linear and/or circular) and line widths should be added. These numbers are used mostly for technical assessment of the proposal and as such are used extensively in the information presented to the user in the Technical Justification node (Section 5.3.6).

All the relevant values should be filled in, even if exact quantities are not known - reasonable estimates should be entered. Which fields should be filled in depends on the type of observation being created and the OT will issue a validation error if, for example, a line width is not entered for a spectral line project or a polarization percentage is not given, or is below the instrumental limits, when full polarization has been selected. For spectral-line projects, a spectral line flux is mandatory and this should always be entered relative to the continuum (if any). If the line is in absorption, the depth of the line relative to the continuum should be entered as a positive flux density.

For solar observing, the source property panel looks very different. Here, all that is requested is an assesment of whether the solar feature being observed corresponds to an ``active'' or a ``quiet'' Sun. This will be used to select the corect debiasing mode when observing.

VLBI is another special case - more information is required than for solar, but still much less than for a regular ALMA project. An important VLBI-only feature is the ability to request that ``passive phasing'' be used during VLBI-type observing. It was initially only possible to use the science target as the phasing calibrator and thus VLBI was restricted to relatively bright sources ($>$0.5 Jy). However, it is now possible to request that another source be used for this purpose i.e. the phasing solutions found on the calibrator are used during the scan on the science target - VLBI users of the VLA will be familiar with this mode. If the appropriate checkbox is ticked, a nearby (phase) calibrator should be defined in the Calibration Setup node and justified in the TJ node. Note that passive phasing must be used in Phased Array mode.


next up previous contents
Next: Field definitions Up: Field Setup Previous: Resolving source information   Contents
The ALMA OT Team, 2021 Feb 03