Schemas

Correlated Dataset

The Measurement Set v4 schema defines a model of correlated data which can be of visibility (Correlated dataset: Visibility) or spectrum (Correlated dataset: Spectrum) type. These are xarray.Dataset s: collections of Data Arrays and Coordinates sharing the same dimensions, forming a comprehensive view of correlated data. Additional metadata is defined in several Sub-datasets and Info dictionaries. The visibility or spectrum datasets can have one or more visibility, flag, weight, etc. arrays as well as field_and_source_xds sub-datasets, as defined in the Data Groups dictionary.

Correlated dataset: Visibility

class VisibilityXds[source]

Main dataset for interferometric data

	Dimensions	Dtype	Model	Description
Coordinates:
`time`	`[time]`	`<f8`	`TimeCoordArray`	The time coordinate is the mid-point of the nominal sampling interval, as speciﬁed in the `ms_v4.time.attrs['integration_time']` (ms v2 interval). Default: `None`
`baseline_id`	`[baseline_id]`	`<i8` or `<i4`	`BaselineArray`	Baseline ID Default: `None`
`frequency`	`[frequency]`	`<f8`	`FrequencyArray`	Center frequencies for each channel. Default: `None`
`polarization`	`[polarization]`	`<U0`	`PolarizationArray`	Labels for polarization types, e.g. `['XX','XY','YX','YY']`, `['RR','RL','LR','LL']`. Default: `None`
`field_name`	`[time]`	`<U0`		Field name. Default: `None`
`scan_name`	`[time]`	`<U0`	`ScanArray`	Scan name to identify data taken in the same logical scan. Default: `None`
`baseline_antenna1_name`	`[baseline_id]`	`<U0`	`BaselineAntennaNameArray`	Antenna name for 1st antenna in baseline. Maps to `attrs['antenna_xds'].antenna_name` Default: `None`
`baseline_antenna2_name`	`[baseline_id]`	`<U0`	`BaselineAntennaNameArray`	Antenna name for 2nd antenna in baseline. Maps to `attrs['antenna_xds'].antenna_name` Default: `None`
(`polarization_mixed`)	`[baseline_id,polarization]`	`<U0`		If the polarizations are not constant over baseline. For mixed polarizations one would use [‘PP’, ‘PQ’, ‘QP’, ‘QQ’] as the polarization labels and then specify here the actual polarization basis for each baseline using labels from the set of all combinations of ‘X’, ‘Y’, ‘R’ and ‘L’. Default: `None`
(`uvw_label`)	`[uvw_label]`	`<U0`	`UvwLabelArray`	u,v,w Default: `None`
Data Variables:
`VISIBILITY`	`[time,baseline_id,frequency,polarization]`	`<c8` or `<c16`	`VisibilityArray`	Complex visibilities, either simulated or measured by interferometer. Default: `None`
`FLAG`	`[time,baseline_id,frequency,polarization]`	`\|b1` or `\|u1` or `<u2` or `<u4` or `<u8`	`FlagArray`	Flag value. Data is flagged as bad if the array element is `True` or nonzero. If integer, the value should be calculated as `(1 << X_BIT1) \| (1 << X_BIT2) \| ...` for all applying flag reasons as indicated by the `flag_bits` attribute (see also Flag Bits). Default: `None`
`WEIGHT`	`[time,baseline_id,frequency,polarization]`	`<f2` or `<f4` or `<f8`	`WeightArray`	Visibility weights Default: `None`
`UVW`	`[time,baseline_id,uvw_label]`	`<f2` or `<f4` or `<f8`	`UvwArray`	Baseline coordinates from `baseline_antenna2_id` to `baseline_antenna1_id` Default: `None`
(`EFFECTIVE_INTEGRATION_TIME`)	`[time,baseline_id]` or `[time,baseline_id,frequency,polarization]`	`<f8`	`QuantityInSecondsArray`	The integration time, including the effects of missing data, in contrast to `integration_time` attribute of the `time` coordinate, see `TimeArray`. (MS v2: `exposure`). Default: `None`
(`TIME_CENTROID`)	`[time,baseline_id]`	`<f8`	`TimeSamplingArray`	The time centroid of the visibility, includes the effects of missing data unlike the `time` coordinate, see `TimeArray`. Default: `None`
(`TIME_CENTROID_EXTRA_PRECISION`)	`[time,baseline_id]`	`<f8`	`TimeSamplingArray`	Additional precision for `TIME_CENTROID` Default: `None`
(`EFFECTIVE_CHANNEL_WIDTH`)	`[time,baseline_id,frequency,polarization]`	`<f8`	`EffectiveChannelWidthArray`	The channel bandwidth that includes the effects of missing data. Default: `None`
(`FREQUENCY_CENTROID`)	`[frequency]`	`<f8`	`FrequencyCentroidArray`	Includes the effects of missing data unlike `frequency`. Default: `None`
Attributes:
`observation_info`			`ObservationInfoDict`	Default: `None`
`processor_info`			`ProcessorInfoDict`	Default: `None`
`data_groups`			`DataGroupsDict`	Defines groups of correlated data + flag + weight + uvw variables. Default: `None`
`schema_version`			`str`	Semantic version of MSv4 data format. Default: `None`
`creator`			`CreatorDict`	Creator information (software, version). Default: `None`
`creation_date`			`str`	Date visibility dataset was created. Format: YYYY-MM-DDTHH:mm:ss.SSS (ISO 8601) Default: `None`
`type`			`'visibility'` or `'radiometer'`	Dataset type Default: `'visibility'`

Correlated dataset: Spectrum

class SpectrumXds[source]

Main dataset for single dish data

	Dimensions	Dtype	Model	Description
Coordinates:
`time`	`[time]`	`<f8`	`TimeCoordArray`	The time coordinate is the mid-point of the nominal sampling interval, as speciﬁed in the `ms_v4.time.attrs['integration_time']` (ms v2 interval). Default: `None`
`antenna_name`	`[antenna_name]`	`<U0`	`AntennaNameArray`	antenna_name Default: `None`
`frequency`	`[frequency]`	`<f8`	`FrequencyArray`	Center frequencies for each channel. Default: `None`
`polarization`	`[polarization]`	`<U0`	`PolarizationArray`	Labels for polarization types, e.g. `['XX','XY','YX','YY']`, `['RR','RL','LR','LL']`. Default: `None`
`field_name`	`[time]`	`<U0`		Field name. Default: `None`
`scan_name`	`[time]`	`<U0`	`ScanArray`	Arbitary scan name to identify data taken in the same logical scan. Default: `None`
(`polarization_mixed`)	`[antenna_name,polarization]`	`<U0`		If the polarizations are not constant over antennas. For mixed polarizations one would use [‘PP’, ‘PQ’, ‘QP’, ‘QQ’] as the polarization labels and then specify here the actual polarization basis for each antenna using labels from the set of combinations of ‘X’, ‘Y’, ‘R’ and ‘L’. Default: `None`
Data Variables:
`SPECTRUM`	`[time,antenna_name,frequency,polarization]`	`<f2` or `<f4` or `<f8`	`SpectrumArray`	Single dish data, either simulated or measured by an antenna. Default: `None`
`FLAG`	`[time,antenna_name,frequency,polarization]`	`\|b1` or `\|u1` or `<u2` or `<u4` or `<u8`	`FlagArray`	Flag value. Data is flagged as bad if the array element is `True` or nonzero. If integer, the value should be calculated as `(1 << X_BIT1) \| (1 << X_BIT2) \| ...` for all applying flag reasons as indicated by the `flag_bits` attribute (see also Flag Bits). Default: `None`
`WEIGHT`	`[time,antenna_name,frequency,polarization]`	`<f2` or `<f4` or `<f8`	`WeightArray`	Visibility weights Default: `None`
(`EFFECTIVE_INTEGRATION_TIME`)	`[time,antenna_name]` or `[time,antenna_name,frequency,polarization]`	`<f8`	`QuantityInSecondsArray`	The integration time, including the effects of missing data, in contrast to `integration_time` attribute of the `time` coordinate, see `TimeArray`. (MS v2: `exposure`). Default: `None`
(`TIME_CENTROID`)	`[time,antenna_name]`	`<f8`	`TimeSamplingArray`	The time centroid of the visibility, includes the effects of missing data unlike the `time` coordinate, see `TimeArray`. Default: `None`
(`TIME_CENTROID_EXTRA_PRECISION`)	`[time,antenna_name]`	`<f8`	`TimeSamplingArray`	Additional precision for `TIME_CENTROID` Default: `None`
(`EFFECTIVE_CHANNEL_WIDTH`)	`[time,antenna_name,frequency,polarization]`	`<f8`	`EffectiveChannelWidthArray`	The channel bandwidth that includes the effects of missing data. Default: `None`
(`FREQUENCY_CENTROID`)	`[frequency]`	`<f8`	`FrequencyCentroidArray`	Includes the effects of missing data unlike `frequency`. Default: `None`
Attributes:
`observation_info`			`ObservationInfoDict`	Default: `None`
`processor_info`			`ProcessorInfoDict`	Default: `None`
`data_groups`			`DataGroupsDict`	Defines groups of correlated data + flag + weight variables. Default: `None`
`schema_version`			`str`	Semantic version of MSv4 data format. Default: `None`
`creator`			`CreatorDict`	Creator information (software, version). Default: `None`
`creation_date`			`str`	Date spectrum dataset was created . Format: YYYY-MM-DDTHH:mm:ss.SSS (ISO 8601) Default: `None`
`type`			`'spectrum'`	Dataset type Default: `'spectrum'`

Sub-datasets

antenna_xds

class AntennaXds[source]

Antenna dataset: global antenna properties for each antenna.

	Dimensions	Dtype	Model	Description
Coordinates:
`antenna_name`	`[antenna_name]`	`<U0`	`AntennaNameArray`	Antenna name Default: `None`
`station_name`	`[antenna_name]`	`<U0`		Name of the station pad (relevant to arrays with moving antennas). Default: `None`
`mount`	`[antenna_name]`	`<U0`		Mount type of the antenna. Reserved keywords include: ”EQUATORIAL” - equatorial mount; ”ALT-AZ”: azimuth-elevation mount; “ALT-AZ+ROTATOR”: alt-az mount with feed rotator; introduced for ASKAP dishes; “ALT-AZ+NASMYTH-R”: Nasmyth mount with receivers at the right-hand side of the cabin. Many high-frequency antennas used for VLBI have such a mount typel; “ALT-AZ+NASMYTH-L”: Nasmyth mount with receivers at the left-hand side of the cabin. “ALT-AZ+BWG-R”: alt-az mount that uses a Beam Wave Guide to bring the focus down to the pedestal. The receivers are at the right-hand side of the cabin (-R). Compared to the Nasmyth mounts there is an extra correction term because there are now two rotating mirrors. See https://arxiv.org/abs/2210.13381 for more details. “ALT-AZ+BWG-L”: alt-az mount that uses a Beam Wave Guide, as above, but with receivers at the left-hand side of the cabin. ”X-Y”: x-y mount; ”SPACE-HALCA” - specific orientation model. Default: `None`
`telescope_name`	`[antenna_name]`	`<U0`		Useful when data is combined from mutiple arrays for example ACA + ALMA. Default: `None`
`receptor_label`	`[receptor_label]`	`<U0`		Names of receptors Default: `None`
`polarization_type`	`[antenna_name,receptor_label]`	`<U0`		Polarization type to which each receptor responds (e.g. ”R”,”L”,”X” or ”Y”). This is the receptor polarization type as recorded in the final correlated data (e.g. ”RR”); i.e. as measured after all polarization combiners. [‘X’,’Y’], [‘R’,’L’] Default: `None`
(`cartesian_pos_label`)	`[cartesian_pos_label]`	`<U0`		(x,y,z) - either cartesian or ellipsoid Default: `None`
(`ellipsoid_dir_label`)	`[ellipsoid_dir_label]`	`<U0`		(lon, lat, dist) - either cartesian or ellipsoid Default: `None`
(`ellipsoid_dis_label`)	`[ellipsoid_dis_label]`	`<U0`		(lon, lat, dist) - either cartesian or ellipsoid Default: `None`
Data Variables:
`ANTENNA_POSITION`	`[antenna_name,ellipsoid_dir_label]` or `[antenna_name,ellipsoid_dis_label]` or `[antenna_name,cartesian_pos_label]`	`<f8`	`LocationArray`	In a right-handed frame, X towards the intersection of the equator and the Greenwich meridian, Z towards the pole. Default: `None`
(`ANTENNA_DISH_DIAMETER`)	`[antenna_name]`	`<f8`	`QuantityInMetersArray`	The diameter of the main reflector (or the largest dimension for non-circular apertures). Default: `None`
(`ANTENNA_EFFECTIVE_DISH_DIAMETER`)	`[antenna_name]`	`<f8`	`QuantityInMetersArray`	Effective dish diameter used in computing beam model (such as airy disk). Default: `None`
(`ANTENNA_BLOCKAGE`)	`[antenna_name]`	`<f8`	`QuantityInMetersArray`	Blockage caused by secondary reflector used in computing beam model (such as airy disk). Default: `None`
(`ANTENNA_RECEPTOR_ANGLE`)	`[antenna_name,receptor_label]`	`<f8`	`QuantityInRadiansArray`	Polarization reference angle. Converts into parallactic angle in the sky domain. Default: `None`
(`ANTENNA_FOCUS_LENGTH`)	`[antenna_name]`	`<f8`	`QuantityInMetersArray`	Focus length. As defined along the optical axis of the antenna. Default: `None`
Attributes:
(`overall_telescope_name`)			`str`	The name of the collection of arrays and dishes that were used for the observation. In many instances this will only be a single array or dish. An example of a telescope consistening of mutiple arrays and dishes is the EHT. The coordinate telescope_name will give the names of the constituent arrays and dishes. From MSv2 observation table. Default: `None`
(`relocatable_antennas`)			`bool`	Can the antennas be moved (ALMA, VLA, NOEMA) Default: `None`
`type`			`'antenna'`	Type of dataset. Expected to be `antenna` Default: `'antenna'`

field_and_source_xds

class FieldSourceXds[source]

Field positions for each source.

Defines a field position on the sky. For interferometers, this is the correlated field position. For single dishes, this is the nominal pointing direction.

	Dimensions	Dtype	Model	Description
Coordinates:
`source_name`	`[field_name]`	`<U0`		Source name. Default: `None`
`field_name`	`[field_name]`	`<U0`		Field name. Default: `None`
`sky_dir_label`	`[sky_dir_label]`	`<U0`		Coordinate labels of sky directions (typically shape 2 and ‘ra’, ‘dec’) Default: `None`
(`cartesian_pos_label`)	`[cartesian_pos_label]`	`<U0`		Coordinate labels of geocentric earth location data (typically shape 3 and ‘x’, ‘y’, ‘z’) Default: `('x', 'y', 'z')`
(`line_label`)	`[line_label]`	`<U0`		Line labels (for line names and variables). Default: `()`
(`line_names`)	`[field_name,line_label]`	`<U0`		Line names (e.g. v=1, J=1-0, SiO). Default: `()`
Data Variables:
(`FIELD_PHASE_CENTER_DIRECTION`)	`[field_name,sky_dir_label]`	`<f8`	`SkyCoordArray`	Offset from the SOURCE_DIRECTION that gives the direction of phase center for which the fringes have been stopped-that is a point source in this direction will produce a constant measured phase (page 2 of https://articles.adsabs.harvard.edu/pdf/1999ASPC..180…79F). For conversion from MSv2, frame refers column keywords by default. If frame varies with field, it refers DelayDir_Ref column instead. Default: `None`
(`FIELD_REFERENCE_CENTER_DIRECTION`)	`[field_name,sky_dir_label]`	`<f8`	`SkyCoordArray`	Used in single-dish to record the associated reference direction if positionswitching been applied. For conversion from MSv2, frame refers column keywords by default. If frame varies with field, it refers DelayDir_Ref column instead. Default: `None`
(`SOURCE_DIRECTION`)	`[field_name,sky_dir_label]`	`<f8`	`SkyCoordArray`	CASA Table Cols: RA,DEC,Rho.”Astrometric RA and Dec and Geocentric distance with respect to the observer’s location (Geocentric). “Adjusted for light-time aberration only. With respect to the reference plane and equinox of the chosen system (ICRF or FK4/B1950). If the FK4/B1950 frame output is selected, elliptic aberration terms are added. Astrometric RA/DEC is generally used when comparing or reducing data against a star catalog.” https://ssd.jpl.nasa.gov/horizons/manual.html : 1. Astrometric RA & DEC Default: `None`
(`LINE_REST_FREQUENCY`)	`[field_name,line_label]`	`<f8`	`SpectralCoordArray`	Rest frequencies for the transitions. Default: `None`
(`LINE_SYSTEMIC_VELOCITY`)	`[field_name,line_label]`	`<f8`	`QuantityInMetersPerSecondArray`	Systemic velocity at reference Default: `None`
(`OBSERVER_POSITION`)	`[cartesian_pos_label]`	`<f8`	`LocationArray`	Observer location. Default: `None`
Attributes:
(`doppler_shift_velocity`)			`'ratio'` or `'m/s'`	Velocity definition of the Doppler shift, e.g., RADIO or OPTICAL velocity in m/s Default: `None`
(`source_model_url`)			`str`	URL to access source model Default: `None`
`type`			`'field_and_source'`	Type of dataset. Default: `'field_and_source'`

class FieldSourceEphemerisXds[source]

Field positions for each source, when the source have ephemeris information.

Defines a field position on the sky. For interferometers, this is the correlated field position. For single dishes, this is the nominal pointing direction.

	Dimensions	Dtype	Model	Description
Coordinates:
`source_name`	`[time]`	`<U0`		Source name. Default: `None`
`field_name`	`[time]`	`<U0`		Field name. Default: `None`
`time`	`[time]`	`<f8`	`TimeInterpolatedCoordArray`	Midpoint of time for which this set of parameters is accurate. Labeled ‘time’ when interpolated to main time Default: `None`
(`sky_dir_label`)	`[sky_dir_label]`	`<U0`		Coordinate labels of sky directions (typically shape 2 and ‘ra’, ‘dec’) Default: `('ra', 'dec')`
(`sky_dis_label`)	`[sky_dis_label]`	`<U0`		Coordinate lables of sky distance (typically shape 1 and ‘dist’) Default: `'dist'`
(`ellipsoid_dir_label`)	`[ellipsoid_dir_label]`	`<U0`		Default: `('lon', 'lat')`
(`ellipsoid_dis_label`)	`[ellipsoid_dis_label]`	`<U0`		Coordinate labels of geodetic earth location data (typically shape 3 and ‘lon’, ‘lat’, ‘height’) Default: `'height'`
(`cartesian_pos_label`)	`[cartesian_pos_label]`	`<U0`		Coordinate labels of geocentric earth location data (typically shape 3 and ‘x’, ‘y’, ‘z’) Default: `('x', 'y', 'z')`
(`line_label`)	`[line_label]`	`<U0`		Line labels (for line names and variables). Default: `()`
(`line_names`)	`[field_name,line_label]`	`<U0`		Line names (e.g. v=1, J=1-0, SiO). Default: `()`
(`time_ephemeris`)	`[time_ephemeris]`	`<f8`	`TimeEphemerisCoordArray`	Midpoint of time for which this set of parameters is accurate. Labeled ‘time_ephemeris’ when not interpolating to main time Default: `()`
Data Variables:
(`FIELD_PHASE_CENTER_DIRECTION`)	`[time,sky_dir_label]` or `[time,sky_dis_label]`	`<f8`	`SkyCoordArray`	Offset from the SOURCE_DIRECTION that gives the direction of phase center for which the fringes have been stopped-that is a point source in this direction will produce a constant measured phase (page 2 of https://articles.adsabs.harvard.edu/pdf/1999ASPC..180…79F). For conversion from MSv2, frame refers column keywords by default. If frame varies with field, it refers DelayDir_Ref column instead. Default: `None`
(`FIELD_PHASE_CENTER_DISTANCE`)	`[time,sky_dir_label]` or `[time,sky_dis_label]`	`<f8`	`SkyCoordArray`	Offset from the SOURCE_DIRECTION that gives the direction of phase center for which the fringes have been stopped-that is a point source in this direction will produce a constant measured phase (page 2 of https://articles.adsabs.harvard.edu/pdf/1999ASPC..180…79F). For conversion from MSv2, frame refers column keywords by default. If frame varies with field, it refers DelayDir_Ref column instead. Default: `None`
(`FIELD_REFERENCE_CENTER_DIRECTION`)	`[time,sky_dir_label]` or `[time,sky_dis_label]`	`<f8`	`SkyCoordArray`	Used in single-dish to record the associated reference direction if positionswitching been applied. For conversion from MSv2, frame refers column keywords by default. If frame varies with field, it refers DelayDir_Ref column instead. Default: `None`
(`FIELD_REFERENCE_CENTER_DISTANCE`)	`[time,sky_dir_label]` or `[time,sky_dis_label]`	`<f8`	`SkyCoordArray`	Used in single-dish to record the associated reference direction if positionswitching been applied. For conversion from MSv2, frame refers column keywords by default. If frame varies with field, it refers DelayDir_Ref column instead. Default: `None`
(`LINE_REST_FREQUENCY`)	`[time,line_label]`	`<f8`	`SpectralCoordArray`	Rest frequencies for the transitions. Default: `None`
(`LINE_SYSTEMIC_VELOCITY`)	`[time,line_label]`	`<f8`	`QuantityInMetersPerSecondArray`	Systemic velocity at reference Default: `None`
(`SOURCE_LOCATION`)	`[time,sky_dir_label]` or `[time,sky_dis_label]` or `[time_ephemeris,sky_dir_label]` or `[time_ephemeris,sky_dis_label]`	`<f8`	`SkyCoordArray`	CASA Table Cols: RA,DEC,Rho.”Astrometric RA and Dec and Geocentric distance with respect to the observer’s location (Geocentric). “Adjusted for light-time aberration only. With respect to the reference plane and equinox of the chosen system (ICRF or FK4/B1950). If the FK4/B1950 frame output is selected, elliptic aberration terms are added. Astrometric RA/DEC is generally used when comparing or reducing data against a star catalog.” https://ssd.jpl.nasa.gov/horizons/manual.html : 1. Astrometric RA & DEC Default: `None`
(`SOURCE_RADIAL_VELOCITY`)	`[time]` or `[time_ephemeris]`	`<f8`	`QuantityInMetersPerSecondArray`	CASA Table Cols: RadVel. Geocentric distance rate Default: `None`
(`NORTH_POLE_POSITION_ANGLE`)	`[time]` or `[time_ephemeris]`	`<f8`	`QuantityInRadiansArray`	CASA Table cols: NP_ang, “Targets’ apparent north-pole position angle (counter-clockwise with respect to direction of true-of-date reference-frame north pole) and angular distance from the sub-observer point (center of disc) at print time. A negative distance indicates the north-pole is on the hidden hemisphere.” https://ssd.jpl.nasa.gov/horizons/manual.html : 17. North pole position angle & distance from disc center. Default: `None`
(`NORTH_POLE_ANGULAR_DISTANCE`)	`[time]` or `[time_ephemeris]`	`<f8`	`QuantityInRadiansArray`	CASA Table cols: NP_dist, “Targets’ apparent north-pole position angle (counter-clockwise with respect to direction of true-of date reference-frame north pole) and angular distance from the sub-observer point (center of disc) at print time. A negative distance indicates the north-pole is on the hidden hemisphere.”https://ssd.jpl.nasa.gov/horizons/manual.html : 17. North pole position angle & distance from disc center. Default: `None`
(`SUB_OBSERVER_DIRECTION`)	`[time,ellipsoid_dir_label]` or `[time,ellipsoid_dis_label]` or `[time,cartesian_pos_label]` or `[time_ephemeris,ellipsoid_dir_label]` or `[time_ephemeris,ellipsoid_dis_label]` or `[time_ephemeris,cartesian_pos_label]`	`<f8`	`LocationArray`	CASA Table cols: DiskLong, DiskLat. “Apparent planetodetic longitude and latitude of the center of the target disc seen by the OBSERVER at print-time. This is not exactly the same as the “nearest point” for a non-spherical target shape (since the center of the disc might not be the point closest to the observer), but is generally very close if not a very irregular body shape. The IAU2009 rotation models are used except for Earth and MOON, which use higher-precision models. For the gas giants Jupiter, Saturn, Uranus and Neptune, IAU2009 longitude is based on the “System III” prime meridian rotation angle of the magnetic field. By contrast, pole direction (thus latitude) is relative to the body dynamical equator. There can be an offset between the magnetic pole and the dynamical pole of rotation. Down-leg light travel-time from target to observer is taken into account. Latitude is the angle between the equatorial plane and perpendicular to the reference ellipsoid of the body and body oblateness thereby included. The reference ellipsoid is an oblate spheroid with a single flatness coefficient in which the y-axis body radius is taken to be the same value as the x-axis radius. Whether longitude is positive to the east or west for the target will be indicated at the end of the output ephemeris.” https://ssd.jpl.nasa.gov/horizons/manual.html : 14. Observer sub-longitude & sub-latitude Default: `None`
(`SUB_SOLAR_POSITION`)	`[time,ellipsoid_dir_label]` or `[time,ellipsoid_dis_label]` or `[time,cartesian_pos_label]` or `[time_ephemeris,ellipsoid_dir_label]` or `[time_ephemeris,ellipsoid_dis_label]` or `[time_ephemeris,cartesian_pos_label]`	`<f8`	`LocationArray`	CASA Table cols: Sl_lon, Sl_lat, r. “Heliocentric distance along with “Apparent sub-solar longitude and latitude of the Sun on the target. The apparent planetodetic longitude and latitude of the center of the target disc as seen from the Sun, as seen by the observer at print-time. This is _NOT_ exactly the same as the “sub-solar” (nearest) point for a non-spherical target shape (since the center of the disc seen from the Sun might not be the closest point to the Sun), but is very close if not a highly irregular body shape. Light travel-time from Sun to target and from target to observer is taken into account. Latitude is the angle between the equatorial plane and the line perpendicular to the reference ellipsoid of the body. The reference ellipsoid is an oblate spheroid with a single flatness coefficient in which the y-axis body radius is taken to be the same value as the x-axis radius. Uses IAU2009 rotation models except for Earth and Moon, which uses a higher precision models. Values for Jupiter, Saturn, Uranus and Neptune are Set III, referring to rotation of their magnetic fields. Whether longitude is positive to the east or west for the target will be indicated at the end of the output ephemeris.” https://ssd.jpl.nasa.gov/horizons/manual.html : 15. Solar sub-longitude & sub-latitude Default: `None`
(`HELIOCENTRIC_RADIAL_VELOCITY`)	`[time]` or `[time_ephemeris]`	`<f8`	`QuantityInMetersPerSecondArray`	CASA Table cols: rdot.”The Sun’s apparent range-rate relative to the target, as seen by the observer. A positive “rdot” means the target was moving away from the Sun, negative indicates movement toward the Sun.” https://ssd.jpl.nasa.gov/horizons/manual.html : 19. Solar range & range-rate (relative to target) Default: `None`
(`OBSERVER_PHASE_ANGLE`)	`[time]` or `[time_ephemeris]`	`<f8`	`QuantityInRadiansArray`	CASA Table cols: phang.””phi” is the true PHASE ANGLE at the observers’ location at print time. “PAB-LON” and “PAB-LAT” are the FK4/B1950 or ICRF/J2000 ecliptic longitude and latitude of the phase angle bisector direction; the outward directed angle bisecting the arc created by the apparent vector from Sun to target center and the astrometric vector from observer to target center. For an otherwise uniform ellipsoid, the time when its long-axis is perpendicular to the PAB direction approximately corresponds to lightcurve maximum (or maximum brightness) of the body. PAB is discussed in Harris et al., Icarus 57, 251-258 (1984).” https://ssd.jpl.nasa.gov/horizons/manual.html : Phase angle and bisector Default: `None`
(`OBSERVER_POSITION`)	`[ellipsoid_dir_label]` or `[ellipsoid_dis_label]` or `[cartesian_pos_label]`	`<f8`	`LocationArray`	Observer location. Default: `None`
Attributes:
(`doppler_shift_velocity`)			`'ratio'` or `'m/s'`	Velocity definition of the Doppler shift, e.g., RADIO or OPTICAL velocity in m/s Default: `None`
(`source_model_url`)			`str`	URL to access source model Default: `None`
(`ephemeris_name`)			`str`	The name of the ephemeris. For example DE430. This can be used with Astropy solar_system_ephemeris.set(‘DE430’), see https://docs.astropy.org/en/stable/coordinates/solarsystem.html. Default: `None`
`type`			`'field_and_source_ephemeris'`	Type of dataset. Default: `'field_and_source_ephemeris'`

pointing_xds

class PointingXds[source]

Pointing dataset: antenna pointing information.

In the past the relationship and definition of the pointing information has not been clear. Here we attempt to clarify it by explaining the relationship between the ASDM, MSv2 and MSv4 pointing information.

The following abreviations are used:

M2: Measurement Set version 2
M4: Measurement Set version 4
A : ASDM

The following definitions come from the ASDM’s SDM Tables Short Description page 97-99:

A_encoder: The values measured from the antenna. They may be however affected by metrology, if applied. Note that for ALMA this column will contain positions obtained using the AZ POSN RSP and EL POSN RSP monitor points of the ACU and not the GET AZ ENC and GET EL ENC monitor points (as these do not include the metrology corrections). It is agreed that the the vendor pointing model will never be applied. AZELNOWAntenna.position
A_pointingDirection: This is the commanded direction of the antenna. It is obtained by adding the target and offset columns, and then applying the pointing model referenced by PointingModelId. The pointing model can be the composition of the absolute pointing model and of a local pointing model. In that case their coefficients will both be in the PointingModel table.
A_target: This is the field center direction (as given in the Field Table), possibly affected by the optional antenna-based sourceOffset. This column is in horizontal coordinates. AZELNOWAntenna.position
A_offset: Additional offsets in horizontal coordinates (usually meant for measuring the pointing corrections, mapping the antenna beam, …). AZELNOWAntenna.positiontarget
A_sourceOffset : Optionally, the antenna-based mapping offsets in the field. These are in the equatorial system, and used, for instance, in on-the-fly mapping when the antennas are driven independently across the field.

M2_DIRECTION = rotate(A_target,A_offset) #A_target is rotated to by A_offset

if withPointingCorrection : M2_DIRECTION = rotate(A_target,A_offset) + (A_encoder - A_pointingDirection)

M2_TARGET = A_target M2_POINTING_OFFSET = A_offset M2_ENCODER = A_encoder

It should be noted that definition of M2_direction is not consistent, it depends if withPointingCorrection is set to True or False (see the importasdm documenation and code for details).

M4_DIRECTION = M2_DIRECTION (withPointingCorrection=True) M4_ENCODER = M2_ENCODER

	Dimensions	Dtype	Model	Description
Coordinates:
`antenna_name`	`[antenna_name]`	`<U0`	`AntennaNameArray`	Antenna name, as specified by baseline_antenna1/2_name in visibility dataset Default: `None`
`local_sky_dir_label`	`[local_sky_dir_label]`	`<U0`		Direction labels. Default: `None`
(`time`)	`[time]`	`<f8`	`TimeInterpolatedCoordArray`	Mid-point of the time interval for which the information in this row is valid. Required to use the same time measure reference as in visibility dataset. Labeled ‘time’ when interpolating to main time axis. Default: `None`
(`time_pointing`)	`[time_pointing]`	`<f8`	`TimePointingCoordArray`	Midpoint of time for which this set of parameters is accurate. Labeled ‘time_pointing’ when not interpolating to main time axis Default: `None`
(`n_polynomial`)	`[n_polynomial]`	`<i8`		Polynomial index, when using polynomial coefficients to specify POINTING_BEAM Default: `None`
Data Variables:
`POINTING_BEAM`	`[time,antenna_name,local_sky_dir_label]` or `[time_pointing,antenna_name,local_sky_dir_label]` or `[time,antenna_name,local_sky_dir_label,n_polynomial]` or `[time_pointing,antenna_name,local_sky_dir_label,n_polynomial]`	`<f8`	`PointingBeamArray`	The direction of the peak response of the beam and is equavalent to the MSv2 DIRECTION (M2_direction) with_pointing_correction=True, optionally expressed as polynomial coefficients. Default: `None`
(`POINTING_DISH_MEASURED`)	`[time,antenna_name,local_sky_dir_label]` or `[time_pointing,antenna_name,local_sky_dir_label]`	`<f8`	`LocalSkyCoordArray`	The current encoder values on the primary axes of the mount type for the antenna. ENCODER in MSv2 (M2_encoder). Default: `None`
(`POINTING_OVER_THE_TOP`)	`[time,antenna_name]` or `[time_pointing,antenna_name]`	`\|b1`		True if the antenna was driven to this position ”over the top” (az-el mount). Default: `None`
Attributes:
`type`			`'pointing'`	Type of dataset. Default: `'pointing'`

weather_xds

class WeatherXds[source]

Weather dataset: station positions and time-dependent mean external atmosphere and weather information

	Dimensions	Dtype	Model	Description
Coordinates:
`station_name`	`[station_name]`	`<U0`		Station name Default: `None`
(`time`)	`[time]`	`<f8`	`TimeInterpolatedCoordArray`	Mid-point of the time interval. Labeled ‘time’ when interpolated to main time axis Default: `None`
(`time_weather`)	`[time_weather]`	`<f8`	`TimeWeatherCoordArray`	Mid-point of the time interval. Labeled ‘time_weather’ when not interpolated to main time axis Default: `None`
(`ellipsoid_dir_label`)	`[ellipsoid_dir_label]`	`<U0`		Coordinate labels of geodetic earth location data (typically shape 2 and ‘lon’, ‘lat’) Default: `('lon', 'lat')`
(`ellipsoid_dis_label`)	`[ellipsoid_dis_label]`	`<U0`		Coordinate labels of geodetic earth height data (typically shape 1 and ‘height’) Default: `('height',)`
(`cartesian_pos_label`)	`[cartesian_pos_label]`	`<U0`		Coordinate labels of geocentric earth location data (typically shape 3 and ‘x’, ‘y’, ‘z’) Default: `('x', 'y', 'z')`
Data Variables:
`STATION_POSITION`	`[station_name,ellipsoid_dir_label]` or `[station_name,ellipsoid_dis_label]` or `[station_name,cartesian_pos_label]`	`<f8`	`LocationArray`	Position of the weather station Default: `None`
(`H2O`)	`[station_name,time]` or `[station_name,time_weather]`	`<f8`	`QuantityInPerSquareMetersArray`	Average column density of water, in zenith direction (rather than line of sight) Default: `None`
(`IONOS_ELECTRON`)	`[station_name,time]` or `[station_name,time_weather]`	`<f8`	`QuantityInPerSquareMetersArray`	Average column density of electrons, in zenith direction (rather than line of sight) Default: `None`
(`PRESSURE`)	`[station_name,time]` or `[station_name,time_weather]`	`<f8`	`QuantityInPascalArray`	Ambient atmospheric pressure Default: `None`
(`REL_HUMIDITY`)	`[station_name,time]` or `[station_name,time_weather]`	`<f8`		Ambient relative humidity Default: `None`
(`TEMPERATURE`)	`[station_name,time]` or `[station_name,time_weather]`	`<f8`	`QuantityInKelvinArray`	Ambient air temperature for an antenna Default: `None`
(`DEW_POINT`)	`[station_name,time]` or `[station_name,time_weather]`	`<f8`	`QuantityInKelvinArray`	Dew point Default: `None`
(`WIND_DIRECTION`)	`[station_name,time]` or `[station_name,time_weather]`	`<f8`	`QuantityInRadiansArray`	Average wind direction Default: `None`
(`WIND_SPEED`)	`[station_name,time]` or `[station_name,time_weather]`	`<f8`	`QuantityInMetersPerSecondArray`	Average wind speed Default: `None`
Attributes:
`type`			`'weather'`	Type of dataset. Default: `'weather'`

system_calibration_xds

class SystemCalibrationXds[source]

System calibration dataset: time- and frequency- variable calibration measurements for each antenna, as indexed on receptor

	Dimensions	Dtype	Model	Description
Coordinates:
`antenna_name`	`[antenna_name]`	`<U0`	`AntennaNameArray`	Antenna name Default: `None`
`station_name`	`[antenna_name]`	`<U0`		Name of the station pad (relevant to arrays with moving antennas). Default: `None`
`receptor_label`	`[receptor_label]`	`<U0`		Names of receptors Default: `None`
`polarization_type`	`[antenna_name,receptor_label]`	`<U0`		Polarization type to which each receptor responds (e.g. ”R”,”L”,”X” or ”Y”). This is the receptor polarization type as recorded in the final correlated data (e.g. ”RR”); i.e. as measured after all polarization combiners. [‘X’,’Y’], [‘R’,’L’] Default: `None`
(`time`)	`[time]`	`<f8`	`TimeInterpolatedCoordArray`	Midpoint of time for which this set of parameters is accurate. Labeled ‘time’ when interpolating to main time axis Default: `None`
(`time_system_cal`)	`[time_system_cal]`	`<f8`	`TimeSystemCalCoordArray`	Midpoint of time for which this set of parameters is accurate. Labeled ‘time_system_cal’ when not interpolating to main time axis Default: `None`
(`frequency`)	`[frequency]`	`<f8`	`FrequencyArray`	Center frequencies for each channel. Default: `None`
(`frequency_system_cal`)	`[frequency_system_cal]`	`<i8`		TODO: What is this? Default: `None`
Data Variables:
(`PHASE_DIFFERENCE`)	`[antenna_name,time_system_cal]` or `[antenna_name,time]`	`<f8`	`QuantityInRadiansArray`	Phase difference between receptor 0 and receptor 1 Default: `None`
(`TCAL`)	`[antenna_name,time_system_cal,receptor_label,frequency_system_cal]` or `[antenna_name,time_system_cal,receptor_label,frequency]` or `[antenna_name,time_system_cal,receptor_label]` or `[antenna_name,time,receptor_label,frequency_system_cal]` or `[antenna_name,time,receptor_label,frequency]` or `[antenna_name,time,receptor_label]`	`<f8`	`QuantityInKelvinArray`	Calibration temp Default: `None`
(`TRX`)	`[antenna_name,time_system_cal,receptor_label,frequency_system_cal]` or `[antenna_name,time_system_cal,receptor_label,frequency]` or `[antenna_name,time_system_cal,receptor_label]` or `[antenna_name,time,receptor_label,frequency_system_cal]` or `[antenna_name,time,receptor_label,frequency]` or `[antenna_name,time,receptor_label]`	`<f8`	`QuantityInKelvinArray`	Receiver temperature Default: `None`
(`TSKY`)	`[antenna_name,time_system_cal,receptor_label,frequency_system_cal]` or `[antenna_name,time_system_cal,receptor_label,frequency]` or `[antenna_name,time_system_cal,receptor_label]` or `[antenna_name,time,receptor_label,frequency_system_cal]` or `[antenna_name,time,receptor_label,frequency]` or `[antenna_name,time,receptor_label]`	`<f8`	`QuantityInKelvinArray`	Sky temperature Default: `None`
(`TSYS`)	`[antenna_name,time_system_cal,receptor_label,frequency_system_cal]` or `[antenna_name,time_system_cal,receptor_label,frequency]` or `[antenna_name,time_system_cal,receptor_label]` or `[antenna_name,time,receptor_label,frequency_system_cal]` or `[antenna_name,time,receptor_label,frequency]` or `[antenna_name,time,receptor_label]`	`<f8`	`QuantityInKelvinArray`	System temperature Default: `None`
(`TANT`)	`[antenna_name,time_system_cal,receptor_label,frequency_system_cal]` or `[antenna_name,time_system_cal,receptor_label,frequency]` or `[antenna_name,time_system_cal,receptor_label]` or `[antenna_name,time,receptor_label,frequency_system_cal]` or `[antenna_name,time,receptor_label,frequency]` or `[antenna_name,time,receptor_label]`	`<f8`	`QuantityInKelvinArray`	Antenna temperature Default: `None`
(`TANT_SYS`)	`[antenna_name,time_system_cal,receptor_label,frequency_system_cal]` or `[antenna_name,time_system_cal,receptor_label,frequency]` or `[antenna_name,time_system_cal,receptor_label]` or `[antenna_name,time,receptor_label,frequency_system_cal]` or `[antenna_name,time,receptor_label,frequency]` or `[antenna_name,time,receptor_label]`	`<f8`	`QuantityInKelvinArray`	TANT/TSYS Default: `None`
Attributes:
`type`			`'system_calibration'`	Type of dataset. Default: `'system_calibration'`

gain_curve_xds

class GainCurveXds[source]

Gain curve dataset. See See https://casacore.github.io/casacore-notes/265.pdf for a full description.

	Dimensions	Dtype	Model	Description
Coordinates:
`antenna_name`	`[antenna_name]`	`<U0`	`AntennaNameArray`	Antenna name Default: `None`
`station_name`	`[antenna_name]`	`<U0`		Name of the station pad (relevant to arrays with moving antennas). Default: `None`
`mount`	`[antenna_name]`	`<U0`		Mount type of the antenna. Reserved keywords include: ”EQUATORIAL” - equatorial mount; ”ALT-AZ”: azimuth-elevation mount; “ALT-AZ+ROTATOR”: alt-az mount with feed rotator; introduced for ASKAP dishes; “ALT-AZ+NASMYTH-R”: Nasmyth mount with receivers at the right-hand side of the cabin. Many high-frequency antennas used for VLBI have such a mount typel; “ALT-AZ+NASMYTH-L”: Nasmyth mount with receivers at the left-hand side of the cabin. “ALT-AZ+BWG-R”: alt-az mount that uses a Beam Wave Guide to bring the focus down to the pedestal. The receivers are at the right-hand side of the cabin (-R). Compared to the Nasmyth mounts there is an extra correction term because there are now two rotating mirrors. See https://arxiv.org/abs/2210.13381 for more details. “ALT-AZ+BWG-L”: alt-az mount that uses a Beam Wave Guide, as above, but with receivers at the left-hand side of the cabin. ”X-Y”: x-y mount; ”SPACE-HALCA” - specific orientation model. Default: `None`
`telescope_name`	`[antenna_name]`	`<U0`		Useful when data is combined from mutiple arrays for example ACA + ALMA. Default: `None`
`receptor_label`	`[receptor_label]`	`<U0`		Names of receptors Default: `None`
`polarization_type`	`[antenna_name,receptor_label]`	`<U0`		Polarization type to which each receptor responds (e.g. ”R”,”L”,”X” or ”Y”). This is the receptor polarization type as recorded in the final correlated data (e.g. ”RR”); i.e. as measured after all polarization combiners. [‘X’,’Y’], [‘R’,’L’] Default: `None`
(`gain_curve_type`)	`[antenna_name]`	`<U0`		Gain curve type. Reserved keywords include: (”POWER(EL)” - Power as a function of elevation; ”POWER(ZA)” - Power as a function of zenith angle; ”VOLTAGE(EL)” - Voltage as a function of elevation; ”VOLTAGE(ZA)” - Voltage as a function of zenith angle). See https://casacore.github.io/casacore-notes/265.pdf Default: `None`
`poly_term`	`[poly_term]`	`<i8`		Term orders in gain curve polynomial Default: `None`
Data Variables:
`GAIN_CURVE`	`[antenna_name,poly_term,receptor_label]`	`<f8`		Coeﬃcients of the polynomial that describes the (power or voltage) gain. Default: `None`
`GAIN_CURVE_INTERVAL`	`[antenna_name]`	`<f8`	`QuantityInSecondsArray`	Time interval. Default: `None`
`GAIN_CURVE_SENSITIVITY`	`[antenna_name,receptor_label]`	`<f8`	`QuantityInKelvinPerJanskyArray`	Sensitivity of the antenna expressed in K/Jy. This is what AIPS calls “DPFU”. Default: `None`
Attributes:
`measured_date`			`str`	Date gain curve was measured. Format: YYYY-MM-DDTHH:mm:ss.SSS (ISO 8601) Default: `None`
`type`			`'gain_curve'`	Type of dataset. Expected to be `gain_curve` Default: `'gain_curve'`

phase_calibration_xds

class PhaseCalibrationXds[source]

Phase calibration dataset: signal chain phase calibration measurements.

	Dimensions	Dtype	Model	Description
Coordinates:
`antenna_name`	`[antenna_name]`	`<U0`	`AntennaNameArray`	Antenna name Default: `None`
`station_name`	`[antenna_name]`	`<U0`		Name of the station pad (relevant to arrays with moving antennas). Default: `None`
`mount`	`[antenna_name]`	`<U0`		Mount type of the antenna. Reserved keywords include: ”EQUATORIAL” - equatorial mount; ”ALT-AZ”: azimuth-elevation mount; “ALT-AZ+ROTATOR”: alt-az mount with feed rotator; introduced for ASKAP dishes; “ALT-AZ+NASMYTH-R”: Nasmyth mount with receivers at the right-hand side of the cabin. Many high-frequency antennas used for VLBI have such a mount typel; “ALT-AZ+NASMYTH-L”: Nasmyth mount with receivers at the left-hand side of the cabin. “ALT-AZ+BWG-R”: alt-az mount that uses a Beam Wave Guide to bring the focus down to the pedestal. The receivers are at the right-hand side of the cabin (-R). Compared to the Nasmyth mounts there is an extra correction term because there are now two rotating mirrors. See https://arxiv.org/abs/2210.13381 for more details. “ALT-AZ+BWG-L”: alt-az mount that uses a Beam Wave Guide, as above, but with receivers at the left-hand side of the cabin. ”X-Y”: x-y mount; ”SPACE-HALCA”: specific orientation model. Default: `None`
`telescope_name`	`[antenna_name]`	`<U0`		Useful when data is combined from mutiple arrays for example ACA + ALMA. Default: `None`
`receptor_label`	`[receptor_label]`	`<U0`		Names of receptors Default: `None`
`polarization_type`	`[antenna_name,receptor_label]`	`<U0`		Polarization type to which each receptor responds (e.g. ”R”,”L”,”X” or ”Y”). This is the receptor polarization type as recorded in the final correlated data (e.g. ”RR”); i.e. as measured after all polarization combiners. [‘X’,’Y’], [‘R’,’L’] Default: `None`
(`time`)	`[time]`	`<f8`	`TimeInterpolatedCoordArray`	Time for VLBI phase cal Default: `None`
(`time_phase_cal`)	`[time_phase_cal]`	`<f8`		Time for VLBI phase cal Default: `None`
(`tone_label`)	`[tone_label]`	`<U0`		Phase-cal tones that are measured. This number may vary by antenna, and may vary by spectral window as well, especially if spectral windows of varying widths are supported Default: `None`
Data Variables:
`PHASE_CAL`	`[antenna_name,time,receptor_label,tone_label]` or `[antenna_name,time_phase_cal,receptor_label,tone_label]`	`<c8` or `<c16`		Phase calibration measurements. These are provided as complex values that represent both the phase and amplitude for a measured phase-cal tone. Measurements are provided as a two-dimensional array such that separate measurements can be provided for each receptor of a feed (so separate values for each polarization) for each of the measured tones. See https://casacore.github.io/casacore-notes/265.pdf Default: `None`
`PHASE_CAL_CABLE_CAL`	`[antenna_name,time]` or `[antenna_name,time_phase_cal]`	`<f8`	`QuantityInSecondsArray`	Cable calibration measurement. This is a measurement of the delay in the cable that provides the reference signal to the receiver. There should be only a single reference signal per feed (even if that feed has multiple receptors) so this is provided as a simple scalar. See https://casacore.github.io/casacore-notes/265.pdf Default: `None`
`PHASE_CAL_INTERVAL`	`[antenna_name,time]` or `[antenna_name,time_phase_cal]`	`<f8`	`QuantityInSecondsArray`	Time interval. See https://casacore.github.io/casacore-notes/265.pdf Default: `None`
`PHASE_CAL_TONE_FREQUENCY`	`[antenna_name,time,receptor_label,tone_label]` or `[antenna_name,time_phase_cal,receptor_label,tone_label]`	`<f8`	`QuantityInHertzArray`	The sky frequencies of each measured phase-cal tone. See https://casacore.github.io/casacore-notes/265.pdf Default: `None`
Attributes:
`type`			`'phase_calibration'`	Type of dataset. Expected to be `phase_calibration` Default: `'phase_calibration'`

phased_array_xds

class PhasedArrayXds[source]

Phased array dataset: define stations made of multiple receiver elements.

	Dimensions	Dtype	Model	Description
Coordinates:
`antenna_name`	`[antenna_name]`	`<U0`	`AntennaNameArray`	Antenna name Default: `None`
`element_id`	`[element_id]`	`<i8` or `<i4`		Element Id within a station/antenna Default: `None`
`receptor_label`	`[receptor_label]`	`<U0`		Names of receptors, i.e. polarization hands. Default: `None`
`polarization_type`	`[antenna_name,receptor_label]`	`<U0`		Polarization type to which each receptor responds (e.g. ”R”,”L”,”X” or ”Y”). This is the receptor polarization type as recorded in the final correlated data (e.g. ”RR”); i.e. as measured after all polarization combiners. [‘X’,’Y’], [‘R’,’L’] Default: `None`
`cartesian_pos_label`	`[cartesian_pos_label]`	`<U0`		(x,y,z) - either cartesian or ellipsoid Default: `None`
`cartesian_pos_label_local`	`[cartesian_pos_label_local]`	`<U0`		(p,q,r) - cartesian station-local frame of reference Default: `None`
Data Variables:
`PHASED_ARRAY_COORDINATE_AXES`	`[antenna_name,cartesian_pos_label_local,cartesian_pos_label]`	`<f8`	`PhasedArrayCoordinateAxesArray`	3x3 Rotation M such that X_geo = M X_local. Used to convert PHASED_ARRAY_ELEMENT_OFFSET coordinates from a station-local frame to a geocentric frame. Default: `None`
`PHASED_ARRAY_ELEMENT_OFFSET`	`[antenna_name,cartesian_pos_label_local,element_id]`	`<f8`	`PhasedArrayElementOffsetArray`	Offsets of each array element from its parent station position, expressed in a station-local frame. Station positions are stored in antenna_xds.ANTENNA_POSITION. Default: `None`
`PHASED_ARRAY_ELEMENT_FLAG`	`[antenna_name,receptor_label,element_id]`	`\|b1`		Boolean flag set to True if the data from a given polarisation receptor of a station element should be ignored. Default: `None`
Attributes:
`type`			`'phased_array'`	Type of dataset. Expected to be `phased_array` Default: `None`

Info dictionaries

Observation info

class ObservationInfoDict[source]

ObservationInfoDict(observer: ‘list[str]’, release_date: ‘str’, project_UID: ‘str’, execution_block_UID: ‘Optional[str]’, session_reference_UID: ‘Optional[str]’, observing_log: ‘Optional[str]’, scheduling_block_UID: ‘Optional[str]’)

	Dtype	Description
Fields:
`observer`	`list[str]`	List of observer names. Default: `None`
`release_date`	`str`	Project release date. This is the date on which the data may become public. Format: YYYY-MM-DDTHH:mm:ss.SSS (ISO 8601) Default: `None`
`project_UID`	`str`	Project UID/code. When populated from an ASDM, the entityId string of the projectUID attribute of the ExecBlock table. Default: `None`
(`execution_block_UID`)	`str`	From ASDM: The archive’s UID of the execution block. Intended to be populated with the entityId string of the execBlockUID attribute of the ExecBlock table. Default: `None`
(`session_reference_UID`)	`str`	From ASDM: The observing session reference. Intended to be populated with the entityId string of the sessionReference attribute of the ExecBlock table Default: `None`
(`observing_log`)	`str`	The observing log, as supplied by the telescope or instrument. Or also from ASDM: Logs of the observation during this execution block. When taken from an ASDM, it is intended to be populated with the values of the observingLog attribute of the ExecBlock table. Default: `None`
(`scheduling_block_UID`)	`str`	From ASDM: The scheduling block archive’s UID. Intended to be populated with the entityId string of the sbSummaryUID attribute of the SBSummary table. Default: `None`

Processor info

class ProcessorInfoDict[source]

ProcessorInfoDict(type: ‘str’, sub_type: ‘str’)

Dimensions

Dtype

Model

Description

Fields:

type

str

Processor type; reserved keywords include (”CORRELATOR” - interferometric correlator; ”SPECTROMETER” - single-dish correlator; ”RADIOMETER” - generic detector/integrator).

Default: None

sub_type

str

Processor sub-type, e.g. ”GBT” or ”JIVE”.

Default: None

Data Groups dictionary

class DataGroupsDict[source]

Dictionary of data group dictionaries. A ‘base’ data group is mandatory. Additional data groups can be added with different names.

	Dimensions	Dtype	Model	Description
Fields:
`base`		`dict`		Default: `None`

Data Group dictionary

class DataGroupDict[source]

Defines a group of correlated data + flag + weight + uvw variables.

	Dtype	Description
Fields:
`correlated_data`	`str`	Name of the correlated data variable, for example ‘VISIBILITY’ or ‘VISIBILITY_MODEL’. Default: `None`
`flag`	`str`	Name of the flag variable, for example ‘FLAG’. Default: `None`
`weight`	`str`	Name of the weight variable of the group, for example ‘WEIGHT’. Default: `None`
(`uvw`)	`str`	Name of the UVW variable of the group, for example ‘UVW’. Default: `None`
`field_and_source`	`str`	Name of the field_and_source_xds, for example field_and_source_base_xds. Default: `None`
`description`	`str`	More details about the data group. Default: `None`
`date`	`str`	Creation date-time, in ISO 8601 format: ‘YYYY-MM-DDTHH:mm:ss.SSS’. Default: `None`

Creator dictionary

class CreatorDict[source]

CreatorDict(software_name: ‘str’, version: ‘str’)

Dimensions

Dtype

Model

Description

Fields:

software_name

str

Software that created the Measurement Set (XRadio, etc.).

Default: None

version

str

Version of the software.

Default: None

Data Arrays

Models of correlated data xarray.DataArray s. Bulk data gathered into Correlated Dataset.

class VisibilityArray[source]

Visibility data array in main dataset (interferometric data, VisibilityXds)

	Dimensions	Dtype	Model	Description
`data`	`[time,baseline_id,frequency,polarization]`	`<c8` or `<c16`	`VisibilityArray`
Coordinates:
`time`	`[time]`	`<f8`	`TimeCoordArray`	Time, expressed in seconds since the epoch (see `scale` & `format`), see also see `TimeArray`. Default: `None`
`baseline_id`	`[baseline_id]`	`<i8` or `<i4`	`BaselineArray`	Unique id for each baseline. Default: `None`
`polarization`	`[polarization]`	`<U0`	`PolarizationArray`	Polarization names. Default: `None`
`frequency`	`[frequency]`	`<f8`	`FrequencyArray`	Center frequencies for each channel. Default: `None`
Attributes:
(`long_name`)			`str`	Long-form name to use for axis. Should be `"Visibility values"` Default: `'Visibility values'`
`units`			`str`	Default: `'Jy'`
(`allow_multiple_versions`)			`bool`	Default: `True`

class SpectrumArray[source]

Definition of xr.DataArray for SPECTRUM data (single dish)

	Dimensions	Dtype	Model	Description
`data`	`[time,antenna_name,frequency,polarization]`	`<f2` or `<f4` or `<f8`	`SpectrumArray`
Coordinates:
`time`	`[time]`	`<f8`	`TimeCoordArray`	Time, expressed in seconds since the epoch (see `scale` & `format`), see also see `TimeArray`. Default: `None`
`antenna_name`	`[antenna_name]`	`<U0`	`AntennaNameArray`	Unique name for each antenna(_station). Default: `None`
`frequency`	`[frequency]`	`<f8`	`FrequencyArray`	Center frequencies for each channel. Default: `None`
`polarization`	`[polarization]`	`<U0`	`PolarizationArray`	Polarization names. Default: `None`
Attributes:
(`long_name`)			`str`	Long-form name to use for axis. Should be `"Spectrum values"` Default: `'Spectrum values'`
`units`			`str`	Default: `'Jy'`

class FlagArray[source]

An array of Boolean or integer values with the same shape as VISIBILITY or SPECTRUM, representing the cumulative flags applying to this data matrix.

	Dimensions	Dtype	Model	Description
`data`	`[time,baseline_id,frequency,polarization]` or `[time,antenna_name,frequency,polarization]`	`\|b1` or `\|u1` or `<u2` or `<u4` or `<u8`	`FlagArray`	Flag value. Data is flagged as bad if the array element is `True` or nonzero. If integer, the value should be calculated as `(1 << X_BIT1) \| (1 << X_BIT2) \| ...` for all applying flag reasons as indicated by the `flag_bits` attribute (see also Flag Bits).
Coordinates:
`time`	`[time]`	`<f8`	`TimeCoordArray`	Time, expressed in seconds since the epoch (see `scale` & `format`), see also see `TimeArray`. Default: `None`
(`baseline_id`)	`[baseline_id]`	`<i8` or `<i4`	`BaselineArray`	Unique id for each baseline. Default: `None`
(`antenna_name`)	`[antenna_name]`	`<U0`	`AntennaNameArray`	Unique name for each antenna(_station). Default: `None`
`frequency`	`[frequency]`	`<f8`	`FrequencyArray`	Center frequencies for each channel. Default: `None`
(`polarization`)	`[polarization]`	`<U0`	`PolarizationArray`	Polarization names. Default: `None`
Attributes:
(`flag_bits`)			`list[str]`	Labels associated with bits used in `FlagArray` data. See Flag Bits for suggested semantics. Default: `('UNSPECIFIED_BIT', 'STATIC_BIT', 'CAM_BIT', 'DATA_LOST_BIT', 'INGEST_RFI_BIT', 'PREDICTED_RFI_BIT', 'CAL_RFI_BIT', 'POSTPROC_BIT')`
(`long_name`)			`str`	Default: `'Visibility flags'`
(`allow_multiple_versions`)			`bool`	Default: `True`

class WeightArray[source]

The weight for each channel, with the same shape as the associated VisibilityArray or SpectrumArray, as assigned by the correlator or processor.

Weights are channel-dependent in MSv4, and therefore equivalent to the WEIGHT_SPECTRUM column from MSv2. Should be calculated as 1/sigma^2 (sigma root mean square noise).

	Dimensions	Dtype	Model	Description
`data`	`[time,baseline_id,frequency,polarization]` or `[time,antenna_name,frequency,polarization]`	`<f2` or `<f4` or `<f8`	`WeightArray`	Visibility weights
Coordinates:
`time`	`[time]`	`<f8`	`TimeCoordArray`	Time, expressed in seconds since the epoch (see `scale` & `format`), see also see `TimeArray`. Default: `None`
(`baseline_id`)	`[baseline_id]`	`<i8` or `<i4`	`BaselineArray`	Unique id for each baseline. Default: `None`
(`antenna_name`)	`[antenna_name]`	`<U0`	`AntennaNameArray`	Unique name for each antenna(_station). Default: `None`
`frequency`	`[frequency]`	`<f8`	`FrequencyArray`	Center frequencies for each channel. Default: `None`
(`polarization`)	`[polarization]`	`<U0`	`PolarizationArray`	Polarization names. Default: `None`
Attributes:
(`long_name`)			`str`	Default: `'Visibility weights'`
(`allow_multiple_versions`)			`bool`	Default: `True`

class UvwArray[source]

Coordinates for the baseline from baseline_antenna2_id to baseline_antenna1_id, i.e. the baseline is equal to the difference POSITION2 - POSITION1. The UVW given are for the TIME_CENTROID, and correspond in general to the reference type for the field_info.phase_dir.

The baseline direction should be: W towards source direction; V in plane through source and system’s pole; U in direction of increasing longitude coordinate. So citing http://casa.nrao.edu/Memos/CoordConvention.pdf: Consider an XYZ Celestial coordinate system centered at the location of the interferometer, with \(X\) towards the East, \(Z\) towards the NCP and \(Y\) to complete a right-handed system. The UVW coordinate system is then defined by the hour-angle and declination of the phase-reference direction such that

when the direction of observation is the NCP (ha=0,dec=90), the UVW coordinates are aligned with XYZ,
V, W and the NCP are always on a Great circle,
when W is on the local meridian, U points East
when the direction of observation is at zero declination, an hour-angle of -6 hours makes W point due East.

This definition also determines the sign of the phase of VISIBILITY.

	Dimensions	Dtype	Model	Description
`data`	`[time,baseline_id,uvw_label]`	`<f2` or `<f4` or `<f8`	`UvwArray`	Baseline coordinates from `baseline_antenna2_id` to `baseline_antenna1_id`
Coordinates:
`time`	`[time]`	`<f8`	`TimeCoordArray`	Time, expressed in seconds since the epoch (see `scale` & `format`), see also see `TimeArray`. Default: `None`
(`baseline_id`)	`[baseline_id]`	`<i8` or `<i4`	`BaselineArray`	Unique id for each baseline. Default: `None`
`uvw_label`	`[uvw_label]`	`<U0`	`UvwLabelArray`	Should be `('u','v','w')`, used by `UvwArray` Default: `('u', 'v', 'w')`
Attributes:
(`long_name`)			`str`	Long-form name to use for axis. Should be `"Baseline coordinates` Default: `'Baseline coordinates'`
`type`			`'uvw'`	Default: `'uvw'`
`frame`			`'fk5'`, `'icrs'` or `'APP'`	To be defined in astropy (see for example https://github.com/astropy/astropy/issues/7766) Default: `'icrs'`
`units`			`'m'`	Default: `'m'`
(`allow_multiple_versions`)			`bool`	Default: `True`

class TimeSamplingArray[source]

Model of arrays of measures used in the main dataset for data variables such as TIME_CENTROID and TIME_CENTROID_EXTRA_PRECISION.

	Dimensions	Dtype	Model	Description
`data`	`[time,baseline_id]` or `[time,antenna_name]`	`<f8`	`TimeSamplingArray`
Coordinates:
`time`	`[time]`	`<f8`	`TimeCoordArray`	Time, expressed in seconds since the epoch (see `scale` & `format`), see also see `TimeArray`. Default: `None`
(`baseline_id`)	`[baseline_id]`	`<i8` or `<i4`	`BaselineArray`	Unique id for each baseline. Default: `None`
(`antenna_name`)	`[antenna_name]`	`<U0`	`AntennaNameArray`	Unique name for each antenna(_station). Default: `None`
Attributes:
`scale`			`'tai'`, `'tcb'`, `'tcg'`, `'tdb'`, `'tt'`, `'ut1'` or `'utc'`	Astropy time scales, see `astropy.time.Time` Default: `'utc'`
`format`			`'unix'`, `'mjd'`, `'cxcsec'` or `'gps'`	Astropy format, see `astropy.time.Time`. Default seconds from 1970-01-01 00:00:00 UTC Default: `'unix'`
(`long_name`)			`str`	Default: `'Time sampling data'`
`units`			`'s'`	Default: `'s'`

class EffectiveChannelWidthArray[source]

Model of frequency related data variables of the main dataset, such as EFFECTIVE_CHANNEL_WIDTH.

	Dimensions	Dtype	Model	Description
`data`	`[time,baseline_id,frequency,polarization]` or `[time,antenna_name,frequency,polarization]`	`<f8`	`EffectiveChannelWidthArray`	Data about frequency sampling, such as centroid or integration time. Concrete function depends on concrete data array within `VisibilityXds` or `SpectrumXds`.
Coordinates:
`frequency`	`[frequency]`	`<f8`	`FrequencyArray`	Center frequencies for each channel. Default: `None`
(`time`)	`[time]`	`<f8`	`TimeCoordArray`	Time, expressed in seconds since the epoch (see `scale` & `format`), see also see `TimeArray`. Default: `None`
(`baseline_id`)	`[baseline_id]`	`<i8` or `<i4`	`BaselineArray`	Unique id for each baseline. Default: `None`
(`polarization`)	`[polarization]`	`<U0`	`PolarizationArray`	Polarization names. Default: `None`
Attributes:
(`long_name`)			`str`	Default: `'Frequency sampling data'`
`units`			`'Hz'`	Default: `'Hz'`
`observer`			`'REST'`, `'BARY'`, `'TOPO'`, `'gcrs'`, `'icrs'`, `'hcrs'`, `'lsrk'`, `'lsrd'` or `'lsr'`	Astropy velocity reference frames (see Using the SpectralCoord Class). Note that Astropy does not use the name ‘topo’ (telescope centric) velocity frame, rather it assumes if no velocity frame is given that this is the default. Default: `'icrs'`

class FrequencyCentroidArray[source]

Model of frequency related data variables of the main dataset, such as FREQUENCY_CENTROID.

	Dimensions	Dtype	Model	Description
`data`	`[frequency]`	`<f8`	`FrequencyCentroidArray`	Data about frequency sampling, such as centroid or integration time. Concrete function depends on concrete data array within `VisibilityXds` or `SpectrumXds`.
Coordinates:
`frequency`	`[frequency]`	`<f8`	`FrequencyArray`	Center frequencies for each channel. Default: `None`
Attributes:
(`long_name`)			`str`	Default: `'Frequency sampling data'`
`units`			`'Hz'`	Default: `'Hz'`
`observer`			`'REST'`, `'BARY'`, `'TOPO'`, `'gcrs'`, `'icrs'`, `'hcrs'`, `'lsrk'`, `'lsrd'` or `'lsr'`	Astropy velocity reference frames (see Using the SpectralCoord Class). Note that Astropy does not use the name ‘topo’ (telescope centric) velocity frame, rather it assumes if no velocity frame is given that this is the default. Default: `'icrs'`

class PointingBeamArray[source]

Pointing beam data array in PointingXds.

	Dimensions	Dtype	Model	Description
`data`	`[time,antenna_name,local_sky_dir_label]` or `[time_pointing,antenna_name,local_sky_dir_label]` or `[time,antenna_name,local_sky_dir_label,n_polynomial]` or `[time_pointing,antenna_name,local_sky_dir_label,n_polynomial]`	`<f8`	`PointingBeamArray`
Attributes:
`type`			`'sky_coord'`	Default: `'sky_coord'`
`units`			`'m'` or `'rad'`	Default: `'rad'`
`frame`			`'icrs'`, `'fk5'`, `'fk4'`, `'fk4noterms'`, `'galactic'`, `'galactocentric'`, `'supergalactic'`, `'altaz'`, `'hadec'`, `'gcrs'`, `'cirs'`, `'itrs'`, `'hcrs'`, `'teme'`, `'tete'`, `'precessedgeocentric'`, `'geocentricmeanecliptic'`, `'barycentricmeanecliptic'`, `'heliocentricmeanecliptic'`, `'geocentrictrueecliptic'`, `'barycentrictrueecliptic'`, `'heliocentrictrueecliptic'`, `'heliocentriceclipticiau76'`, `'custombarycentricecliptic'`, `'lsr'`, `'lsrk'`, `'lsrd'` or `'galacticlsr'`	Blank = use the phase tracking frame of vis. Default: `'icrs'`

class LocalSkyCoordArray[source]

Measures array for the arrays that have coordinate local_sky_dir_label in PointingXds

	Dimensions	Dtype	Model	Description
`data`	`[local_sky_dir_label]`	`<f8`	`LocalSkyCoordArray`
Attributes:
`type`			`'sky_coord'`	Default: `'sky_coord'`
`units`			`'m'` or `'rad'`	Default: `'rad'`
`frame`			`'icrs'`, `'fk5'`, `'fk4'`, `'fk4noterms'`, `'galactic'`, `'galactocentric'`, `'supergalactic'`, `'altaz'`, `'hadec'`, `'gcrs'`, `'cirs'`, `'itrs'`, `'hcrs'`, `'teme'`, `'tete'`, `'precessedgeocentric'`, `'geocentricmeanecliptic'`, `'barycentricmeanecliptic'`, `'heliocentricmeanecliptic'`, `'geocentrictrueecliptic'`, `'barycentrictrueecliptic'`, `'heliocentrictrueecliptic'`, `'heliocentriceclipticiau76'`, `'custombarycentricecliptic'`, `'lsr'`, `'lsrk'`, `'lsrd'` or `'galacticlsr'`	From `fixvis` docs: `clean` and the `im` tool ignore the reference frame claimed by the UVW column (it is often mislabelled as ITRF when it is really FK5 or J2000) and instead assume the (u, v, w)s are in the same frame as the phase tracking center. `calcuvw` does not yet force the UVW column and field centers to use the same reference frame! Blank = use the phase tracking frame of vis. Default: `'icrs'`

class PhasedArrayCoordinateAxesArray[source]

Schema for PHASED_ARRAY_COORDINATE_AXES

	Dimensions	Dtype	Model	Description
`data`	`[antenna_name,cartesian_pos_label_local,cartesian_pos_label]`	`<f8`	`PhasedArrayCoordinateAxesArray`
Attributes:
`units`			`'dimensionless'`	Default: `None`
`type`			`'rotation_matrix'`	Measure type. Should be `"rotation_matrix"`. Default: `None`

class PhasedArrayElementOffsetArray[source]

Schema for PHASED_ARRAY_ELEMENT_OFFSET.

	Dimensions	Dtype	Model	Description
`data`	`[antenna_name,cartesian_pos_label_local,element_id]`	`<f8`	`PhasedArrayElementOffsetArray`
Attributes:
`units`			`'m'`	Default: `None`
`type`			`'location'`	Measure type. Should be `"location"`. Default: `None`
`coordinate_system`			`'topocentric'`	Coordinate system in which the element offsets are expressed. Should be `"topocentric"`. Default: `None`
`origin`			`'ANTENNA_POSITION'`	Origin of the coordinate system. Should be `"ANTENNA_POSITION"`. Default: `None`

Coordinates

Define fundamental dimensions of Xradio data, and associate them with values. The shape of all arrays contained in Xradio datasets will be defined by a mapping of dimensions to sizes – the “shape” of the array. For instance, a data array might have an associated channel or time step count. Use Coordinates to associate dimension indicies with values such as frequencies or timestamps.

class TimeCoordArray[source]

Data model of the main dataset time axis. See also TimeArray.

	Dimensions	Dtype	Model	Description
`data`	`[time]`	`<f8`	`TimeCoordArray`	Time, expressed in seconds since the epoch (see `scale` & `format`), see also see `TimeArray`.
Attributes:
`type`			`'time'`	Coordinate type. Should be `"time"`. Default: `'time'`
`units`			`'s'`	Units to associate with axis Default: `'s'`
`scale`			`'tai'`, `'tcb'`, `'tcg'`, `'tdb'`, `'tt'`, `'ut1'` or `'utc'`	Astropy time scales, see `TimeArray` Default: `'utc'`
`format`			`'unix'`, `'mjd'`, `'cxcsec'` or `'gps'`	Astropy format, see `TimeArray` Default: `'unix'`
`integration_time`			`QuantityInSecondsArray`	The nominal sampling interval (ms v2). Units of seconds. Default: `None`

class BaselineArray[source]

Model of the baseline_id coordinate in the main dataset (interferometric data, VisibilityXds)

	Dimensions	Dtype	Model	Description
`data`	`[baseline_id]`	`<i8` or `<i4`	`BaselineArray`	Unique id for each baseline.
Attributes:
(`long_name`)			`str`	Default: `'Baseline ID'`

class AntennaNameArray[source]

Model of the antenna_name coordinate, used in the main dataset (single dish data, VisibilityXds) and several sub-datasets such as antenna_xds, pointing_xds, weather_xds, system_calibration_xds, gain_curve_xds, etc.

	Dimensions	Dtype	Model	Description
`data`	`[antenna_name]`	`<U0`	`AntennaNameArray`	Unique name for each antenna(_station).
Attributes:
(`long_name`)			`str`	Default: `'Antenna name'`

class BaselineAntennaNameArray[source]

Array of antenna_name by baseline_id, as used in main_xds and main_sd_xds (antenna_name by baseline_id dim

	Dimensions	Dtype	Model	Description
`data`	`[baseline_id]`	`<U0`	`BaselineAntennaNameArray`	Unique id for each baseline.
Attributes:
(`long_name`)			`str`	Default: `'Antenna name by baseline_id'`

class FrequencyArray[source]

Frequency coordinate in the main dataset.

	Dimensions	Dtype	Model	Description
`data`	`[frequency]`	`<f8`	`FrequencyArray`	Center frequencies for each channel.
Attributes:
`spectral_window_name`			`str`	Name associated with spectral window. Default: `None`
`spectral_window_intents`			`list[str]`	An intent string that identifies the intention of the spectral window, for example continuum, spectral line, etc. See Spectral Window Intents for possible values. Default: `None`
(`frequency_group_name`)			`str`	Name associated with frequency group - needed for multi-band VLBI fringe-fitting. Default: `None`
`reference_frequency`			`SpectralCoordArray`	A frequency representative of the spectral window, usually the sky frequency corresponding to the DC edge of the baseband. Used by the calibration system if a ﬁxed scaling frequency is required or in algorithms to identify the observing band. Default: `None`
`channel_width`			`QuantityInHertzArray`	The nominal channel bandwidth. Same units as data array (see units key). Default: `None`
(`doppler`)			`DopplerArray`	Doppler tracking information Default: `None`
`type`			`'spectral_coord'`	Coordinate type. Should be `"spectral_coord"`. Default: `'spectral_coord'`
(`long_name`)			`str`	Long-form name to use for axis Default: `'Frequency'`
`units`			`'Hz'`	Units to associate with axis Default: `'Hz'`
`observer`			`'REST'`, `'BARY'`, `'TOPO'`, `'gcrs'`, `'icrs'`, `'hcrs'`, `'lsrk'`, `'lsrd'` or `'lsr'`	Astropy velocity reference frames (see Using the SpectralCoord Class). Note that Astropy does not use the name ‘topo’ (telescope centric) velocity frame, rather it assumes if no velocity frame is given that this is the default. Default: `'icrs'`

class PolarizationArray[source]

Possible correlations that can be formed from polarised receptors. Possible values, taken from Measures/Stokes.h:

I, Q, U, V (standard stokes parameters)
RR, RL, LR, LL (circular correlation products)
XX, XY, YX, YY (linear correlation products)
RX, RY, LX, LY, XR, XL, YR, YL (mixed correlation products)
PP, PQ, QP, QQ (general quasi-orthogonal correlation products)
RCircular, LCircular, Linear (single dish polarization types)
Ptotal (polarized intensity: sqrt(Q²+U²+V²))
Plinear (linearly polarized intensity: sqrt(Q²+U²))
PFtotal (polarization fraction: Ptotal/I)
PFlinear (linear polarization fraction: Plinear/I)
Pangle (linear polarization angle: 0.5 arctan(U/Q) in radians)

Dimensions

Dtype

Model

Description

data

[polarization]

<U0

PolarizationArray

Polarization names.

Attributes:

(long_name)

str

Long-form name to use for axis. Should be "Polarization"

Default: 'Polarization'

class UvwLabelArray[source]

Coordinate axis to make up ("u", "v", "w") tuple, see UvwArray.

Dimensions

Dtype

Model

Description

data

[uvw_label]

<U0

UvwLabelArray

Should be ('u','v','w'), used by UvwArray

Attributes:

(long_name)

str

Long-form name to use for axis. Should be "U/V/W label"

Default: 'U/V/W label'

class ScanArray[source]

Scan number coordinate in the main dataset.

	Dimensions	Dtype	Model	Description
`data`	`[time]`	`<U0`	`ScanArray`	Scan name for each time sample.
Attributes:
`scan_intents`			`list[str]`	An intent string identifies one intention of the scan, such as to calibrate or observe a target. See Scan Intents for possible intent/subintent values. When converting from MSv2, the list of intents is derived from the OBS_MODE column of MSv2 state table (every comma separated value is taken as an intent). A common convention used in the MSv2 OBS_MODE column is to specify multiple intents separated by commas, each of them giving a main intent and a subintent separated by a ‘#’ character. This is represented in this attribute as a list of “intent#subintent” strings. These are a few example lists: [“CALIBRATE_DELAY#ON_SOURCE” , “CALIBRATE_PHASE#ON_SOURCE”, “CALIBRATE_WVR#ON_SOURCE”], [“CALIBRATE_FLUX#ON_SOURCE” , “CALIBRATE_WVR#ON_SOURCE”], [“CALIBRATE_POINTING#ON_SOURCE”, “CALIBRATE_WVR#ON_SOURCE”, “CALIBRATE_DELAY#ON_SOURCE”], [“CALIBRATE_ATMOSPHERE#AMBIENT”, “CALIBRATE_WVR#AMBIENT”], [“CALIBRATE_FOCUS#ON_SOURCE” , “CALIBRATE_WVR#ON_SOURCE”], [“OBSERVE_TARGET#ON_SOURCE”], or [“OBSERVE_TARGE#UNSPECIFIED”]. The list of possible intent and subintent names (see Scan Intents) is derived from the respective ASDM enumerations. Default: `None`
(`long_name`)			`str`	Long-form name to use for axis. Should be `"Scan name"`. Default: `'Scan name'`

class TimeInterpolatedCoordArray[source]

Data model of a time axis when it is interpolated to match the time axis of the main dataset. This can be used in the system_calibration_xds, pointing_xds, weather_xds, field_and_source_info_xds, and phase_cal_xds when their respective time_system_cal, time_pointing, time_weather, time_ephemeris or time_phase_cal are interpolated to the main dataset time. See also TimeArray.

The only difference with respect to the main TimeCoordArray is the absence of the attribute integration_time

	Dimensions	Dtype	Model	Description
`data`	`[time]`	`<f8`	`TimeInterpolatedCoordArray`	Time, expressed in seconds since the epoch (see `scale` & `format`), see also see `TimeArray`.
Attributes:
`type`			`'time'`	Coordinate type. Should be `"time"`. Default: `'time'`
`units`			`'s'`	Units to associate with axis Default: `'s'`
`scale`			`'tai'`, `'tcb'`, `'tcg'`, `'tdb'`, `'tt'`, `'ut1'` or `'utc'`	Astropy time scales, see `TimeArray` Default: `'utc'`
`format`			`'unix'`, `'mjd'`, `'cxcsec'` or `'gps'`	Astropy format, see `TimeArray` Default: `'unix'`

class TimeSystemCalCoordArray[source]

Data model of ‘time_system_cal’ axis (time axis in system_calibration_xds subdataset when not interpolated to the main time axis. See also TimeCoordArray.

	Dimensions	Dtype	Model	Description
`data`	`[time_system_cal]`	`<f8`	`TimeSystemCalCoordArray`	Time, expressed in seconds since the epoch (see `scale` & `format`).
Attributes:
`type`			`'time'`	Coordinate type. Should be `"time_system_cal"`. Default: `'time_system_cal'`
`units`			`'s'`	Units to associate with axis Default: `'s'`
`scale`			`'tai'`, `'tcb'`, `'tcg'`, `'tdb'`, `'tt'`, `'ut1'` or `'utc'`	Astropy time scales, see `TimeArray` Default: `'utc'`
`format`			`'unix'`, `'mjd'`, `'cxcsec'` or `'gps'`	Astropy format, see `TimeArray` Default: `'unix'`

class FrequencySystemCalArray[source]

The frequency_system_cal coordinate of the system calibration dataset. It has only measures data, as opposed to the frequency array of the main dataset.

	Dimensions	Dtype	Model	Description
`data`	`[frequency_system_cal]`	`<f8`	`FrequencySystemCalArray`	Center frequencies for each channel.
Attributes:
`type`			`'spectral_coord'`	Default: `'spectral_coord'`
`units`			`'Hz'`	Units to associate with axis Default: `'Hz'`
`observer`			`'REST'`, `'BARY'`, `'TOPO'`, `'gcrs'`, `'icrs'`, `'hcrs'`, `'lsrk'`, `'lsrd'` or `'lsr'`	Astropy velocity reference frames (see Using the SpectralCoord Class). Note that Astropy does not use the name ‘topo’ (telescope centric) velocity frame, rather it assumes if no velocity frame is given that this is the default. Default: `'icrs'`

class TimeEphemerisCoordArray[source]

Data model of the ‘time_ephemeris’ axis (time axis in the field_and_source_info_xds subdataset when not interpolated to the main time axis. See also TimeCoordArray.

	Dimensions	Dtype	Model	Description
`data`	`[time_ephemeris]`	`<f8`	`TimeEphemerisCoordArray`	Time, expressed in seconds since the epoch (see `scale` & `format`).
Attributes:
`type`			`'time_ephemeris'`	Coordinate type. Should be `"time_ephemeris"`. Default: `'time_ephemeris'`
`units`			`'s'`	Units to associate with axis Default: `'s'`
`scale`			`'tai'`, `'tcb'`, `'tcg'`, `'tdb'`, `'tt'`, `'ut1'` or `'utc'`	Astropy time scales, see `TimeArray` Default: `'utc'`
`format`			`'unix'`, `'mjd'`, `'cxcsec'` or `'gps'`	Astropy format, see `TimeArray` Default: `'unix'`

class TimePointingCoordArray[source]

Data model of the ‘time_pointing’ axis (time axis in pointing_xds subdataset when not interpolated to the main time axis. See also TimeCoordArray.

	Dimensions	Dtype	Model	Description
`data`	`[time_pointing]`	`<f8`	`TimePointingCoordArray`	Time, expressed in seconds since the epoch (see `scale` & `format`).
Attributes:
`type`			`'time_pointing'`	Coordinate type. Should be `"time_pointing"`. Default: `'time_pointing'`
`units`			`'s'`	Units to associate with axis Default: `'s'`
`scale`			`'tai'`, `'tcb'`, `'tcg'`, `'tdb'`, `'tt'`, `'ut1'` or `'utc'`	Astropy time scales, see `TimeArray` Default: `'utc'`
`format`			`'unix'`, `'mjd'`, `'cxcsec'` or `'gps'`	Astropy format, see `TimeArray` Default: `'unix'`

class TimeWeatherCoordArray[source]

Data model of the ‘time_weather’ axis (time axis in the weather_xds subdataset when not interpolated to the main time axis. See also TimeCoordArray.

	Dimensions	Dtype	Model	Description
`data`	`[time_weather]`	`<f8`	`TimeWeatherCoordArray`	Time, expressed in seconds since the epoch (see `scale` & `format`).
Attributes:
`type`			`'time_weather'`	Coordinate type. Should be `"time_weather"`. Default: `'time_weather'`
`units`			`'s'`	Units to associate with axis Default: `'s'`
`scale`			`'tai'`, `'tcb'`, `'tcg'`, `'tdb'`, `'tt'`, `'ut1'` or `'utc'`	Astropy time scales, see `TimeArray` Default: `'utc'`
`format`			`'unix'`, `'mjd'`, `'cxcsec'` or `'gps'`	Astropy format, see `TimeArray` Default: `'unix'`

Value Keys

Scan Intents

Scan intents to be used with VisibilityXds and SpectrumXds, in the scan_intents field of the ScanArray. The format to be used is [intent]#[subintent], where the possible values for [intent] are:

CALIBRATE AMPLI : Amplitude calibration scan
CALIBRATE ANTENNA PHASE : Requested by EVLA.
CALIBRATE ANTENNA POINTING MODEL : Requested by EVLA.
CALIBRATE ANTENNA POSITION : Requested by EVLA.
CALIBRATE APPPHASE ACTIVE : Calculate and apply phasing solutions. Applicable at ALMA.
CALIBRATE APPPHASE PASSIVE : Apply previously obtained phasing solutions. Applicable at ALMA.
CALIBRATE ATMOSPHERE : Atmosphere calibration scan
CALIBRATE BANDPASS : Bandpass calibration scan
CALIBRATE DELAY : Delay calibration scan
CALIBRATE DIFFGAIN : Enable a gain differential target type
CALIBRATE FLUX : flux measurement scan.
CALIBRATE FOCUS : Focus calibration scan. Z coordinate to be derived
CALIBRATE FOCUS X : Focus calibration scan; X focus coordinate to be derived
CALIBRATE FOCUS Y : Focus calibration scan; Y focus coordinate to be derived
CALIBRATE PHASE : Phase calibration scan
CALIBRATE POINTING : Pointing calibration scan
CALIBRATE POL ANGLE :
CALIBRATE POL LEAKAGE :
CALIBRATE POLARIZATION : Polarization calibration scan
CALIBRATE SIDEBAND RATIO : measure relative gains of sidebands.
CALIBRATE WVR : Data from the water vapor radiometers (and correlation data) are used to derive their calibration parameters.
DO SKYDIP : Skydip calibration scan
MAP ANTENNA SURFACE : Holography calibration scan
MAP PRIMARY BEAM : Data on a celestial calibration source are used to derive a map of the primary beam.
MEASURE RFI : Requested by EVLA.
OBSERVE CHECK SOURCE :
OBSERVE TARGET : Target source scan
SYSTEM CONFIGURATION : Requested by EVLA.
TEST : used for development.
UNSPECIFIED : Unspecified scan intent

Possible values for [subintent]:

ON SOURCE : on-source measurement
OFF SOURCE : off-source measurement
MIXED : Pointing measurement, some antennas are on-source, some off-source
REFERENCE : reference measurement (used for boresight in holography).
SCANNING : antennas are scanning.
HOT : hot load measurement.
AMBIENT : ambient load measurement.
SIGNAL : Signal sideband measurement.
IMAGE : Image sideband measurement.
TEST : reserved for development.
UNSPECIFIED : Unspecified

Spectral Window Intents

Spectral window intents to be used in the attribute spectral_window_intent of the frequency coordinate of measurement sets (VisibilityXds and SpectrumXds):

TEST : reserved for development.
UNSPECIFIED : Unspecified SPW intent.
CONTINUUM : Continuum observation.
CUBE : Spectral cube observation.
CUBE_HANNING : Spectral cube observation with Hanning smoothing.

Note: the list is to be extended.

Flag Bits

When FlagArray is integer data type, bits indicate flagging reason (see FLAG data variable and flag_bits attribute in VisibilityXds and SpectrumXds). Suggested flag bits:

UNSPECIFIED_BIT (default bit 0): reserved for unspecified flag reason
STATIC_BIT (default bit 1): predefined static flag list
CAM_BIT (default bit 2): flag based on live CAM information
DATA_LOST_BIT (default bit 3): no data was received
INGEST_RFI_BIT (default bit 4): RFI detected in ingest
PREDICTED_RFI_BIT (default bit 5): RFI predicted from space based pollutants
CAL_RFI_BIT (default bit 6): RFI detected in calibration
POSTPROC_BIT (default bit 7): some correction/postprocessing step could not be applied

These bits are derived from usage in MeerKat (see flags.py).