Pulsar Astrometry HOWTO

A quick overview of the data reduction and astrometry procedure.

a) Data at each epoch needs to be calibrated: final outputs are calibrated pulsar, in-beam [if available] and calibrator data, along with flag commands used. For detailed usage notes, see the autoaips howto file.
b) Preliminary astrometry: apply in-beam self-cal or ionospheric calibration solution to the pulsar data. Final output is a JMFIT position output file for the pulsar, referenced to the standard calibrator position (in-beam if avilable, else nodding cal).
c) To Archive:
- Flag commands (in .x files)
- Calibrated UV data for calibrator and in-beam (on local disk)
- Reduction notes (online via SC)
d) Final calibration: After all epochs of data are avilable, a final calibrator model is to be constructed with calibrated UV data from all epochs, for both the inbeam and the nodding cals. Using these final models, each epoch will be recalibrated and final astrometric positions will be extracted. This ensures that the same model is used for each epoch.
Final output: astrometric positions for targets at each epoch.

Steps along the way, and things to watch out for:

The autoaips howto help file provides a detailed recipe to follow during data reduction. The most updated version of autoaips is available at here. The file autoaips.c has a list of changes between autoaips versions.
All key and log files are available online:
Epoch 1 -- Epoch 2 -- Epoch 3 -- etc.
It is vital to write out flags so that they can be reapplied later. Save these flags in the PSR.x.N file, as in the example below:
```
flag1 = bif=2;eif=2;bchan=12;echan=14;ante=10
flag2 = ante=5;basel=6
flag3 = bchan=1;echan=1
```
Note: NO SPACES! Everything right of the first '=' is directly interpreted by the AIPS task 'UVFLG'. Also, inputs are not cumulative - each flag is independent of previous flags.