Corrections for Sky Frequencies

In all of the SMA data observed before 2007-11-26, there is a labelling error for the sky frequencies that has lead to 1/2 of the chunks labelled with frequencies 1/2 channel step too high, and the other half labelled with frequencies 1/2 channel step too low. With the updated version of smalod (version 2.10 27-Nov-07 or later), the labelling problem has been automatically taken care. For the SMA data fully calibrated in Miriad, a task smasfreq can be used to fix the labelling error if the data in Miriad format keep the information on the original frequency configuration, i.e. 24 spectral windows per sideband with the original channel resolutions. Here is an example to use smasfreq:

smasfreq vis=071123_20_rx0.lsb.calibrated out=071123_20_rx0.lsb.calibrated.sfreq

The task will prompt messages on screen while excuting program:

SMAsfreq: Version 28-Nov-07
Processing input file 071123_20_rx0.lsb.calibrated
Updating the sky frequencies:
chunkID nchan in-sfreq(GHz) out-sfreq(GHz) sdf(MHz)
s 1      32    217.2967  =>  217.2951      -3.250
s 2      64    217.2156  =>  217.2147      -1.625
s 3      64    217.1396  =>  217.1404      -1.625
s 4      32    217.0567  =>  217.0584      -3.250
s 5      32    216.9687  =>  216.9671      -3.250
s 6      32    216.8867  =>  216.8851      -3.250
s 7      32    216.8107  =>  216.8124      -3.250
s 8      32    216.7287  =>  216.7304      -3.250
s 9      32    216.6407  =>  216.6391      -3.250
s10      32    216.5587  =>  216.5571      -3.250
s11      32    216.4827  =>  216.4844      -3.250
s12      32    216.4007  =>  216.4024      -3.250
s13      32    216.3127  =>  216.3111      -3.250
s14      32    216.2307  =>  216.2291      -3.250
s15      32    216.1547  =>  216.1564      -3.250
s16      32    216.0727  =>  216.0744      -3.250
s17      32    215.9847  =>  215.9831      -3.250
s18      32    215.9027  =>  215.9011      -3.250
s19      32    215.8267  =>  215.8284      -3.250
s20      32    215.7447  =>  215.7464      -3.250
s21      32    215.6567  =>  215.6551      -3.250
s22      32    215.5747  =>  215.5731      -3.250
s23      32    215.4987  =>  215.5004      -3.250
s24      32    215.4167  =>  215.4184      -3.250
Copy over      390 records from 071123_20_rx0.lsb.calibrated