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Source
- Source Name: 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. Spaces are replaced by underscores.
- Resolve: Fill in source details by searching for the entered source name in SIMBAD or NED. SIMBAD is checked first and then NED if no match was found. Check the details very carefully! Note that the so-called IAU format e.g. B0218+357, is no longer allowed - an acronym must be placed before the coordinates e.g. JVAS B0218+357.
- Choose a Solar System Object: A number of solar system objects are recognised by the telescope control system and can be selected here. It is also possible to enter an ephemeris for any non-sidereal source. The source coordinates and velocity definitions are not displayed if a solar system object is selected as the system that controls the observations has detailed ephemeris information for each object.
- Name of Object: Recognised objects are:
- Stars: The Sun. This is a special target as it requires that an ephemeris be entered. This can be generated using the Solar Ephemeris Tool that is located within the Science Portal.
- Planets: Mercury, Venus, Mars, Jupiter, Saturn, Uranus and Neptune.
- Satellites: The Moon, Ganymede, Callisto, Io and Titan.
- Dwarf planets: Pluto and Ceres.
- Asteroids: Pallas, Juno and Vesta.
- Ephemeris: Load a JPL HORIZONS format ephemeris5.1. The source name will be extracted from the ephemeris and inserted into the appropriate field.
- Source Coordinates: Note that these fields do not appear for solar-system objects.
- System: Only ICRS or Galactic should be chosen. ICRS is effectively the only system that is supported by the telescope control system and all calibrator positions are measured within this frame. This means that even if FK5 were selected, the position will be interpreted as ICRS and the output image will be in this coordinate system. Given that all ALMA observations are implicitly made in the ICRS frame, the OT will simply change an FK5 label to ICRS during SB generation. The coordinates will not be transformed, but this is not a problem as the offset between ICRS and FK5 is so small (tens of mas). Therefore, the source may not appear at the expected location within the image, but the image coordinate axes will be correct. Any offset would in any case only be noticeable for very high angular resolution observations. If Galactic coordinates are entered, these will be properly converted to ICRS as part of SB generation.
- Sexagesimal display?: ICRS (and FK5) coordinates will be displayed in sexagesimal format if this is ticked (default). Unclicking this will allow input in degrees for these systems.
- RA: Source Right Ascension. Default input formats are sexagesimal for ICRS (or FK5) and degrees for everything else.
- DEC: Source Declination. Ditto.
- Parallax: Source parallax. Note that negative values are possible when resolving the source using an external server. This is due to the parallax being small compared to the measurement error.
- PM RA: Proper motion in the R.A. (cross-declination) direction. Units should be milliarcsec/yr. Proper motions are used to calculate the current source position assuming that the ICRS position refers to Epoch J2000.
- PM DEC: Proper motion in the declination direction. Units should be milliarcsec/yr.
- Source Radial Velocity: Note that these fields do not appear for solar-system objects. The radial velocity of the source can be entered as either a velocity or a redshift. It is used to convert source rest-frame frequencies to their observable (sky) equivalents. The full set of options are:
- Velocity: Upon entering this, the redshift will also be set according to the Doppler Type (velocity definition). For Single Continuum setups, automatic SB generation will set the velocity to zero (in the SB only).
- Doppler Frame: A number of options are available: barycentric, lsrk and topocentric. Heliocentric can also be chosen, but is not currently supported by the telescope control system and during SB generation will be converted to barycentric (these differ by a maximum of approximately 12 m/s). If the frame is changed, no conversion is performed of an already-entered velocity/redshift. If lsrk is selected, the user-entered spectral window frequencies are converted to the barycentric frame when calculating tuning solutions.
- z: Redshift. This is set automatically if a velocity is entered, but the redshift can also be entered and will set the velocity accordingly. For Single Continuum setups, automatic SB generation will set the redshift to zero (in the SB only).
- Doppler Type: This sets the velocity definition (radio, optical or relativistic). Changing this will make the velocity agree with the entered redshift.
- Target Type: The supported observing patterns: ``Individual pointing(s)'' and ``1 Rectangular Field''. All sources in a Science Goal must use the same Target Type.
Next: Expected Source Properties
Up: Field Setup
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The ALMA OT Team, 2018 Sep 25