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Table 1:

MAIN table: Data, coordinates and flags

MAIN table: Data, coordinates and flags


Name	Format	Units	Measure	Comments

Columns

Keywords
MS_VERSION	Float			MS format version
(SORT_COLUMNS)	String			Sort columns
(SORT_ORDER)	String			Sort order

Key
TIME	Double	s	EPOCH	Integration midpoint
(TIME_EXTRA_PREC)	Double	s		extra TIME precision
ANTENNA1	Int			First antenna
ANTENNA2	Int			Second antenna
(ANTENNA3)	Int			Third antenna
FEED1	Int			Feed on ANTENNA1
FEED2	Int			Feed on ANTENNA2
(FEED3)	Int			Feed on ANTENNA3
DATA_DESCRIPTION_ID	Int			Data desc. id.
PROCESSOR_ID	Int			Processor id.
SWITCH_PHASE_ID	Int			Switch phase id.
FIELD_ID	Int			Field id.

Non-key attributes
INTERVAL	Double	s		Sampling interval
EXPOSURE	Double	s		The effective integration time
TIME_CENTROID	Double	s	EPOCH	Time centroid
(PULSAR_BIN)	Int			Pulsar bin number
( PULSAR_GATE_ID)	Int			Pulsar gate id
(INTEG_NUMBER)	Int			Integration number
SUBARRAY_NUM	Int			Subarray number
EXECUTE_ID	Int			Execute id.
STATE_ID	Int			State id.
(BASELINE_REF)	Bool			Reference antenna
UVW	Double(3)	m	UVW	UVW coordinates

MAIN table: continued

Name	Format	Units	Measure	Comments

Data
(DATA)	Complex(N_c,N_f,N_phc)			Complex visibility matrix (synthesis array)
(FLOAT_DATA)	Float(N_c,N_f)			Float data matrix (single dish)
(VIDEO_POINT)	Complex(N_c)			Video point
(LAG_DATA)	Float(N_c,N_l)			Correlation function
SIGMA	Float(N_c)			Estimated rms noise
(SIGMA_SPECTRUM)	Float(N_c,N_f^*)			Estimated rms noise for each channel
WEIGHT	Float(N_c)			Weight of the whole data matrix
(WEIGHT_SPECTRUM)	Float(N_c,N_f^*)			Weight for each channel

Flag information
FLAG	Float(N_c,N_f^*)			Cumulative data flags
FLAG_CATEGORY	Float(N_c,N_f^*,N_cat)			Flag categories
FLAG_ROW	Bool			The row flag

Notes: N_l = number of lags, N_c = number of correlators, N_f = number of frequency channels, N_phc =1 (or 2 if both the atmospheric phase uncorrected AND corrected data are stored); see item PHASE_CORRECTION in table DATA_DESCRIPTION , N_cat = number of flag categories.
Functional Dependencies

MS_VERSION: MSM revision number, expressed as major_revision.minor_revision.
SORT_COLUMNS: Sort indices, in the form “index₁”, “index₂”, ... for the underlying MS. A string containing NONE¹ reflect no sort order.
SORT_ORDER: Sort order as either ASCENDING² or DESCENDING³ .
TIME: Mid-point (not centroid) of data interval.
TIME_EXTRA_PREC: Extra time precision
ANTENNAn: Antenna identifier corresponding to the antenna number n giving a direct index into a row number in the ANTENNA sub-table. For n > 2, triple product data are implied.
FEEDn: Feed number (> 0). For n > 2, triple product data are implied.
DATA_DESCRIPTION_ID: Data descriptor identifier (> 0) providing a direct index into the DATA_DESCRIPTION sub-table row number.
PROCESSOR_ID: Processor identiufier (> 0) providing a direct index into the PROCESSOR sub-table row number.
SWITCH_PHASE_ID: Switching phase identifier (> 0)
FIELD_ID: Field identifier (> 0)
INTERVAL: Data sampling interval. This is nominal data interval and does not include the effects of bad data or partial integration.
EXPOSURE: Effective data interval, including bad and partial averaging. In the ALMA context it is the integration time (or sub-integration time if STATE_IDis > 0)..
TIME_CENTROID
PULSAR_BIN: Pulsar bin number for the data record. Pulsar data may be measured for a limited number of pulse phase bins. The pulse phase bins are described in the PULSAR sub-table and indexed by this bin number.
PULSAR_GATE_ID
INTEG_NUMBER: Original name SCAN_NUMBER; renamed INTEG_NUMBER The enumeration is relative to the observation (ALMA glossary). The enumeration of the observations is implicit; each time INTEG_NUMBER is decrementing from one row to the next in the MAIN table the observation number is implicitly incremented. N.B.: the observation intent is in the STATE sub-table. If absolutely required an OBS_SUMMARY table could be created, referencing to the main via MAIN_IDprovided the MAIN sorted in ascending time, this for efficient access at the OBSERVATION level.
SUBARRAY_NUM: Subarray number was (historicaly) ARRAY_ID. Renamed for clarity (see section 3.3 of the MS definition v2.0) .
N.B. In case of a multi-configuration data set, note that CONFIG_NAME is added in the EXECUTE_SUMMARY table; in that context it is possible to distinguish the case of several sub-arrays and the case of several array configurations.
EXECUTE_ID: This provides access to a row number in the EXECUTE_SUMMARY table. This meta coordinate defines the data base in term of an association of data blocks.
STATE_ID: State identifier (> 0). Would be always 0 if the sub-integration are not considered.
BASELINE_REF: Flag to indicate the original correlator reference antenna for baseline-based correlators. (True for ANTENNA1, False for ANTENNA2)
UVW: uvw coordinates for the baseline between ANTENNA1 and ANTENNA2. This is defined at the centroid time TIME_CENTROID . This could be reconsidered by providing uvw per antenna. This would become implicit if the UVW would be stored per antenna in a sub-table.
(DATA): Cross-correlated data. Not mandatory.
FLOAT_DATA: Auto-correlated single-dish data For ALMA this will be always present
(VIDEO_POINT): The video point for the spectrum, to allow the full reverse transform.
LAG_DATA
SIGMA: The estimated noise for a single channel, for each correlator.
SIGMA_SPECTRUM: The estimated noise for each channel.
WEIGHT: The weight for the whole data matrix for each correlator, as assigned by the correlator or processor.
WEIGHT_SPECTRUM: The weight for each channel in the data matrix, as assigned by the correlator or processor The weight spectrum should be used in preference to the weight, when available.
FLAG: An array of Boolean values with the same shape as DATA representing the cumulative flags applying to this data matrix, as specified in FLAG_CATEGORY . Data are flagged bad if the FLAG array element is True.
FLAG_CATEGORY: An array of flag matrices with the same shape as DATA , but indexed by category. The category identifiers are specified by a keyword CATEGORY , containing an array of string identifiers, attached to the FLAG_CATEGORY column and thus shared by all rows in the MS. The cumulative effect of these flags is reflected in column FLAG . Data are flagged bad if the FLAG array element is True.
FLAG_ROW: True if the entire row is flagged.

Comments:
DATA, FLOAT_DATA, LAG_DATA At least one of these columns should be present in a MeasurementSet. In special cases one or more could be present (e.g. single-dish data used in synthesis imaging or a mix of auto and cross-correlations on a multi-feed single-dish). If only correlation functions are store in the MS, then N_f^* is the maximum number of lags (N_l) specified in the LAG table for this LAG_ID. If both correlation functions and frequency spectra are store in the same MS, then N_f^* is the number of frequency channels and the weight information refers to the frequency spectra only. The units of these columns (eg. ’Jy’) specify whether the data are in flux density units or correlation coefficients.