Apply gain/elevation effect Apply system temperature measurements Correct for incorrect baseline length and instrumental phase. Correct antenna table (when some antennas were off-line)
NOTE: This task will usually be used very early in the data reduction process. It should be used before calibration.
This also invokes corrections of known instrumental phase errors.
The inputs are the equatorial coordinate offsets entered in the following order (NO checking is done for consistency):
dantpos = A1,X1,Y1,Z1,A2,X2,Y2,Z2,A3,X3,Y3,Z3,....The input values are the antenna number and the three equatorial coordinate offsets (entered in units of nanoseconds). These input values are added to the absolute coordinates read from the data. Antenna present in the data but not included in the input value list are treated as having a zero coordinate offset.
The arcane unit of nanoseconds is used for historical compatibililty. Note 1 nanosec = 0.2997 meters.
A collection of parameter files giving the corrections to apply are stored in $MIRCAT. These have names of the form "dantpos.yymmdd" where "yymmdd" is the date of the start of a new array configuration. Baseline corrections are believed to be constant between array configurations.
If a data file is present, you can instruct atfix to read this directly using the indirect parameter input. For example, to read parameters appropriate for a hypothetical array configuration starting on 16 October 2002, use
none Do not apply any system temperature measurements. If the the measurements were applied on-line, they are undone. any Do nothing. Leave the Tsys calibration as is. constant Apply a constant Tsys between successive Tsys measurements. This is the approach used by the on-line system at 3mm wavelength. extrapolate Apply a Tsys value between measurements which accounts for predicted changes in Tsys with elevation and measured weather. interpolate Interpolate a Tsys value between measurements which accounts for predicted changes in Tsys with elevation and measured weather. This is the default.
nogainel This disables applying a instrumental gain/elevation correction to the data. Currently the gains of the antennas are a function of elevation. By default, a correction is made for gain/elevation effects. noinst Do not correct for instrumental baseline effects. By default a phase correction is made for instrumental baseline effects.
By giving a value to this parameter, atfix will fill in any antenna locations that are missing from 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 (e.g. W106 or N3). When giving the station names, these must be in the order of the antennas (i.e. CA01, CA02, CA03 etc).
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 the standard antenna order (not the shuffled order).
If in doubt, see the on-line history of configurations: