Basic Information on tmcal

Task: tmcal
Purpose: Gain/phase/polarization calibration for SMA data.
Categories: calibration

        tmcal is a MIRIAD task which determines calibration corrections
        (both antenna gains and instrumental polarisation characteristics).

Key: vis
        Input visibility data file. No default. The visibility data
        must be in time order.

Key: select
        Standard uv selection. Default is all data.

Key: line
        Standard line-type specification. Multiple channels can be given.
        Generally it is better to give multiple channels, rather than
        averaging them into a `channel-0'. The default is all the channel
        data (or all the wide data, if there is no channel data).

Key: flux
        The values of the I,Q,U Stokes parameters. If no values are
        given, and it is a source known to tmcal, tmcal uses its known
        flux as the default. If tmcal does not know the source, the
        flux is determined by assuming that the rms gain amplitude is 1.
        For a planet, the values are interpreted as brightness temperature
        in Kelvin (planets are assumed to be unpolarised). Otherwise the values
        are assumed to be in Janskys.
 
        If the option `qusolve' is used, the given fluxes for Q and U are
        used as the initial estimates.

Key: refant
        The reference antenna. Default is 1. The reference antenna needs to be
        present throughout the observation, and so needs to be chosen with some
        care. Any solution intervals where the reference antenna is missing are
        discarded.

Key: minants
        The minimum number of antenna that must be present before a
        solution is attempted. Default is 2.

Key: interval
        This gives the solution interval, in minutes. Antenna gains are assumed
        to be constant over the solution interval.

Key: tol
        Error tolerance. The default is 0.001, which should be adequate.

Key: options
        These options determine what TMCAL solves for. Several options
        can be given,separated by commas.
          nopass     Do not apply any passband calibration.
          qusolve    Solve for Q and U fluxes. Good parallactic
                     angle coverage is required for this.
          twoleak    Solve for a "two part" leakage solution,
          onegain    Solve for a single antenna gain, which is assumed to be
                     independent of polarisation. When time-multiplexing of a single
                     feed is used to measure two states (e.g. R and L), then it should
                     be accurate to assume the antenna gains to R and L are the same.