In the Field Setup page, the user is asked for source parameters, the most important of which are the name, coordinates and velocity. The source names should only contain the following characters: a-z, A-Z, 0-9, -,+, _ or a . (full stop). Characters other than these will be removed or replaced when the project is validated.
Apart from Galactic coordinates, the only system that should be used is ICRS. FK5 can be entered, but the observations will be performed as if the coordinates were ICRS. This has very little impact as the difference is small, amounting to a maximum of some tens of mas. The two components of the source proper motion, Dec. and R.A. (cross declination), are both true angles on the sky and are used to convert the given source position to an observable one assuming that it refers to epoch J2000.0.
The ALMA telescope control system recognises a limited number of solar system objects that can be selected from a drop-down list. This same list also allows the use of an ephemeris for any object for which the coordinates as a function of time can be provided. This is loaded as a text file from the local disk and must be in the JPL HORIZONS format. For details on how to generate HORIZONS ephemeris files, please check Appendix A. When using an ephemeris at Phase 1, it is recommended that only a skeletal example be attached to the Science Goal, using a time interval of one day to cover the period over which the observations are likely to take place. An ephemeris is also required for Solar observing and a tool is available in the Science Portal for generating these.
The velocity can be specified using the optical, radio, or relativistic convention. A number of different frames are available and the must useful of these are barycentric, heliocentric5.1, topocentric and lsrk. The velocity is used to convert the rest frequencies of the spectral windows to the observed equivalent and for barycentric and heliocentric, this is done in the same frame i.e. the ``observed'' velocity will remain in that frame. In the case of lsrk though, the OT performs an additional conversion to the barycentric frame. When changing the source velocity reference system between the available options of heliocentric, barycentric, topocentric and lsrk, the OT is not able to convert the velocity and you will be reminded of this via a pop-up dialogue.
The velocities must be sufficiently similar such that all the sources can be observed in a single band. In addition, a maximum of five tunings per Scheduling Block are allowed and thus the sources must be grouped in velocity space in such a way that this limit is not exceeded. The OT will issue an error if this is the case. This issue is explained more in Section 5.3.3.9.