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Basic Information on uvredo
Task: uvredo
Purpose: Recompute various derived quantitues in a uv data-set
Categories: uv analysis
UVREDO recomputes various derived quantities in a uv data-set.
This may be needed if the derived quantities are wrong for some
reason, or if there is a need to change a coordinate system.
For example uvredo can recompute velocity information, thus
allowing conversion between different velocity rest frames.
A patch for handling SMA data has been added into UVREDO in
consideration of the fact that the sky frequency given in the
archived SMA data has been corrected for a part of the tracked
Doppler velocity (the diurnal term and a part of the annual term).
The SMA patch calculates the proper residual Doppler velocity for
each of the data records corresponding to the "corrected sky
frequency".
NOTE: The recomputation relies on a number of parameters in the
data-set, such as "time". It is assumed that this information is
correct. Uv variables that are important are:
For velocity: time and latitu,longitu (or telescop is these are
missing).
Key: vis
The name of the input uv data set. No default.
Key: select
The normal uv selection commands. The default is to select everything.
Key: line
The normal uv linetype in the form:
line,nchan,start,width,step
The default is all channels. Note that if there are multiple
spectral windows, the fitting process is performed on each window
separately.
Key: stokes
The polarization/Stokes parameters to be copied to the output
data-set. The default is to copy the polarisation/Stokes parameters
unchanged.
Key: out
The name of the output uv data-set. There is no default name.
Key: options
This gives extra processing options. Several options can be given,
each separated by commas. They may be abbreviated to the minimum
needed to avoid ambiguity. Possible options are:
'velocity' Recompute velocity information.
'chi' Recompute parallactic angle information.
The following options can be used to turn off calibration corrections.
The default is to apply any calibration present.
'nocal' Do not apply the gains table.
'nopass' Do not apply bandpass corrections.
'nopol' Do not apply polarizatiopn corrections.
'smaveldop' Recompute the veldop for SMA data.
Keyword: dopsour must be given.
Key: dopsour
If options=smaveldop, this gives the source name, on which the Doppler
motions were tracked by the SMA online system.
dopsour is case-sensitive.
Key: doptime
If options=smaveldop, this gives the UT time to calculate the annual
term as a reference value. The offset from this reference value in the
annual term has been used in the SMA online correction to the Doppler
tracked sky frequency in addition to the diurnal term. The keyword
doptime is in the format of [dd,hh,mm,ss.s; 4 values]. The default is
null. If doptime is null, UVREDO reads the residual Doppler velocity
(veldop) of the Doppler tracked source and recomputes the residual
Doppler velocity for each of the selected data records. The residual
Doppler velocity is then stored into the header variable "veldop"
corresponding to the "corrected sky frequency" ("sfreq").
Key: velocity
If options=velocity or options=smaveldop, this gives the rest frame
of the output data-set. Possible values are 'observatory', 'lsr' and
'barycentric'. The default is the rest frame of the input data-set.