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Basic Information on qvack
Task: qvack
Purpose: Flag after change to observing setup
Categories: calibration
Qvack is a Miriad task to flag data for a number of integrations
near an observing setup change. For example, this is used to
flag data that is suspect because the instrument had not settled
correctly after the change in the setup. The visibility data are
should to be in time order.
Key: vis
Input visibility data file. No default.
Key: select
Standard uv data selection. Default is to select all data.
Key: interval
This gives the time interval, in minutes, for which the data are
flagged after a setup change (or before a setup change, if its
value is negative). The default is 0.1, which flags for
the first 6 seconds after a switch.
Key: force
The time interval, in minutes, which indicates the amount of time
that should ellapse before forcing a (virtual) setup change.
Thus you can QVACK on data that has distinct scans but no actual
change in observing setup. Note that this means the first
INTERVAL amount of data is always flagged. The MODE option is
not needed, nor is it used if you set FORCE
Defaults to no forced setup change.
Key: options
Extra processing options. Currently only one exists:
anticipate Normally the interval given by the "interval" keyword
is relative to the time of the first data found with
a new setup. options=anticipate makes it relative
to the time of the last data before a setup change
occurs.
Key: mode
This determines what changes in setup cause flagging. Several
values can be given, separated by commas, and minimum match is used.
Possible values are:
frequency A change in the frequency setup. Do not use this
option if Doppler tracking is used.
source A change in the source observed.
mosaic A change in the observing centre of a mosaiced
observation.