Task atfix includes an algorithm to interpolate measured system temperature values, between measurements, and to correct the visibility data accordingly. In doing this it correctly handles whether a nominal or the measured system temperature value applied to the data on-line. The interpolation algorithm takes into account changes in elevation and meteorological conditions.
tsyscal can be used to change this default behaviour.
This parameter can take on values to revert the data back to the nominal
system temperature value, to make no changes to the system temperature scaling,
to use the most recent system temperature measurement, or to use an
extrapolation (as distinct from interpolation) algorithm in estimating
On the night of an ATCA reconfiguration, a solution for the antenna positions is derived. The practise is to install this solution as the ``standard solution''. The on-line system will then use this solution in subsequent observations in that array configuration. The quality of this solution is important for the ultimate phase calibration of 3mm data.
Experience has shown that often the position solution derived at the time of the reconfiguration is not necessarily the best possible. For example the solution will depend critically on the atmospheric phase stability at the time of the solution, and this might be less than ideal on the night of the reconfiguration. Consequently improved solutions will often be derived at a later time. If improved solutions become available, then 3-mm observers should correct their data accordingly.
Updated solutions are stored in parameter files in the
Miriad system directory
$MIRCAT. These solutions
are distributed via the Miriad update mechanism, and
have file names of the form ``
where ``yymmdd'' is the date of the relevant array reconfiguration.
Task atfix corrects the data for an improved antenna location solution via the dantpos parameter. If an improved solution file is present, you can instruct atfix to read this directly using the indirect parameter input mechanism (see Section 2.5). For example, to use the antenna location solution appropriate for a hypothetical array reconfiguration that happened on 16 October 2002, use
By giving a value to the array parameter, atfix will fill in any antenna locations that are missing in the input visibility file. NOTE: This just fills in missing antenna locations, it does not perform any flagging of shadowed data.
The value given to this parameter is either an array configuration name (e.g. EW352 or 750A) or a list of six station names (``W106'' and ``N3'' are examples of station names). When giving the station names, these must be in the order of the antennas (i.e. CA01, CA02, CA03 etc), regardless of any possible array shuffles.
NOTE: When antennas are in a shuffled order, or for arrays using the north spur, you should generally give the list of station names, as the standard array configuration names assume an antenna orderwhich is probably not correct.
If in doubt the on-line configuration history should be consulted.
Typical inputs to atfix are:
|in=vela.uv||Input visibility dataset.|
|out=vela.fixed.uv||Output corrected visibility dataset.|
|dantpos=@$MIRCAT/dantpos.021016||Antenna location correction.|