Data products of the pointing pipeline

The pointing pipeline outputs several files, written to disc, for further analysis. These are described here.

HDF5 main data product

The main data product of the pointing pipeline is an HDF5 file based on the PointingTable data model. One file per pointing observation is generated. The file is set up to provide all relevant information to construct an offline global pointing model. It contains the following data:

Coordinates:

  • time: middle timestamp in MJD of the central scan of the pointing observation. This corresponds to the time at which the commanded_pointing is calculated. If the central scan is not found then commanded_pointing cannot be calculated and the median of the middle timestamps from all scans is used.

  • antenna: antenna indexes, e.g. 0, 1, 2. Depends on number of antennas.

  • frequency: central frequency in Hz if fitting to gains and frequency at the higher end of the band if fitting to visibilities.

  • receptor: polarisation values, e.g. I, Q, U, V. Depends on polarisation frame used.

  • angle: ["cross-el", "el"]

Data variables (relevant):

  • pointing: pointing offsets in cross-elevation and elevation for all antennas in units of radians

  • weight: inverse square of the uncertainties in the pointing values in radians.

  • expected_width: theoretical voltage beam sizes for all antennas in radians in the horizontal and vertical co-polarisations

  • fitted_width: fitted voltage beam sizes for all antennas in radians in the horizontal and vertical co-polarisations.

  • fitted_width_std: standard deviation on the fitted_width in radians.

  • fitted_height: fitted Gaussian height for all antennas in arbitrary units. Does not depend on angle.

  • fitted_height_std: standard deviation on the fitted_height in arbitrary units. Does not depend on angle.

Attributes (relevant):

  • band_type: observing band, e.g. Band2.

  • scan_mode: mode of performing the pointing observations, e.g. 5point.

  • track_duration: how long the source and discrete pointing offsets were tracked for.

  • discrete_offset: input discrete pointing relative to target, in degrees. These are the on-sky separations between antennas and target in a reference pointing observation.

  • commanded_pointing: commanded pointing at the middle timestamp of the central scan of the pointing observation in radians.

For a full list of data variables and attributes, see the PointingTable definition.

Additional outputs

TXT file

A CSV-type text file is generated with the following header:

AntennaName,
CrossElevationOffset, CrossElevationOffsetStd,
ElevationOffset, ElevationOffsetStd,
ExpectedWidthH, ExpectedWidthV,
FittedWidthH, FittedWidthHStd,
FittedWidthV, FittedWidthVStd,
FittedHeight, FittedHeightStd

The description of values matches the ones of the HDF5, please refer to that above. Contrary to the HDF5 file, the cross-elevation and elevation offsets have their standard deviations listed here, and not the weight values. H stands for horizontal, V stands for vertical co-polarisation.

PNG files

The pipeline produces various plots for validation purposes.

  • Gain amplitudes: The un-normalised gain amplitudes for all antennas across the entire frequency band or sub-bands

  • Gaussian fits: The Gaussian fit in cross-elevation and elevation showing the fitted centre across the entire frequency band or in all sub-bands

  • Pointing offsets: The weighted average of the pointing offsets shown in the Gaussian fits, other fitted parameters, and their uncertainties