Updating SMA Baselines

All data directories contain an 'antennas' file which lists the positions of the antennas in the array; these positions are used to derive the baseline information. After a configuration change, a baseline track is run to determine the new positions of the antennas. These new, correct positions are applied to future science tracks, but earlier tracks (after the antenna moves but before a successful baseline track) are not corrected. This must be done by hand during data reduction.

Often, achieving a good solution to the antenna positions may take a few days or even weeks if the weather is poor. In many cases data has been taken with a reasonable solution, but would benefit from using an even better fit.

See the effects of a poor baseline solution here.

If you have any questions or concerns just email smarequester@cfa.harvard.edu.

To implement these changes, see the MIR Cookbook (sec. 6.4) or the MIRIAD User's Manual (task:uvedit).

The table below lists data sets which require a baseline solution following antenna moves. However, at later dates further baseline tracks are usually taken to refine these solutions. You can find a comprehsive list of all the baseline solutions at Complete List of SMA Antennas Files. This list can be checked to see if revised antenna positions exist for your data set. Remember to confirm that the antennas are still on the same pads. The values are positions given in meters and the adjustments are tiny; you should expect the new value to be only micrometers from your existing value.

* Highly recommended but not required. These are fine tuning corrections to the baseline soltuions.