CASA additions to MS

Introduction

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MS_VERSION

The MeasurementSet format revision number, expressed as ${major}_{revision}$ ${minor}_{revision}$. This version is 2.0. 

SORT_COLUMNS

Sort indices, in the form ${index}_1$ ${index}_2$ $\cdots$, for the underlying MS. A string containing "NONE" reflects no sort order. An example might be SORT_COLUMNS="TIME ANTENNA1 ANTENNA2", to indicate sorting in in time-baseline order.

SORT_ORDER

Sort order as either "ASCENDING" or "DESCENDING".

TIME

Mid-point (not centroid) of data interval.

TIME_EXTRA_PREC

Extra time precision.

ANTENNAn

Antenna number (≥ 0), and a direct index into the ANTENNA sub-table rownr. For n > 2, triple-product data are implied.

FEEDn

Feed number ≥0). For n> 2, triple-product data are implied.

DATA_DESC_ID

Data description identifier (≥0), and a direct index into the DATA_DESCRIPTION sub-table rownr.

PROCESSOR_ID

Processor indentifier (≥0), and a direct index into the PROCESSOR sub-table rownr.

PHASE_ID

Switching phase identifier (≥0)

FIELD_ID

Field identifier (≥0).

INTERVAL

Data sampling interval. This is the nominal data interval and does not include the effects of bad data or partial integration.

EXPOSURE

Effective data interval, including bad data and partial averaging.

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

Pulsar gate identifier (≥0), and a direct index into the PULSAR_GATE sub-table rownr.

SCAN_NUMBER

Arbitrary scan number to identify data taken in the same logical scan. Not required to be unique.

ARRAY_ID

Subarray identifier (≥0), which identifies data in separate subarrays.

OBSERVATION_ID

Observation identifier (≥0), which identifies data from separate observations.

STATE_ID

State identifier (≥0), which identifies information relating to active reference signals or loads.

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 from ANTENNE2 to ANTENNA1, 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 PHASE_DIR of the relevant field. I.e. J2000 if the phase reference direction is given in J2000 coordinates. However, any known reference is valid. Note that the choice of baseline direction and UVW definition (W towards source direction; V in plane through source and system's pole; U in direction of increasing longitude coordinate) also determines the sign of the phase of the recorded data.

UVW2

uvw coordinates for the baseline from ANTENNE3 to ANTENNA1 (triple-product data only), i.e. the baseline is equal to the difference POSITION3 - POSITION1. The UVW given are for the TIME_CENTROID, and correspond in general to the reference type for the PHASE_DIR of the relevant field. I.e. J2000 if the phase reference direction is given in J2000 coordinates. However, any known reference is valid. Note that the choice of baseline direction and UVW definition (W towards source direction; V in plane through source and system's pole; U in direction of increasing longitude coordinate) also determines the sign of the phase of the recorded data.

DATA, FLOAT_DATA, LAG_DATA

At least one of these columns should be present in a given 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 crosscorrelations on a multi-feed single dish). If only correlation functions are stored 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 stored 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 for these columns (eg. 'Jy') specify whether the data are in flux density units or correlation coefficients.

VIDEO_POINT

The video point for the spectrum, to allow the full reverse transform.

SIGMA

The estimated rms noise for a single channel, for each correlator.

SIGMA_SPECTRUM

The estimated rms 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 (see the DATA item above) 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 MeasurementSet. The cumulative effect of these flags is reflected in column FLAG. Data are flagged bad if the FLAG array element is True. See Section 3.1.8 for further details.

FLAG_ROW

True if the entire row is flagged.

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