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F.3 Extension files

Subsidiary data about uv database and image files are written in “extension files.” These include, for example, history records (HI files), plot instructions (PL files), calibration solutions (SN files), ad nauseum. Some extension files can become large. A history file uses 1024 bytes for every 14 history records, a small amount under most circumstances. A plot file is normally small, but the output from GREYS can be as large as one plane of the image and the output of KNTR is larger by a factor of the number of panes in the plot.

The CL (calibration) table contains the total model of the interferometer at each interval. Many of these logical records are blank in the case of most interferometers but, for the VLBA, these records will contain essential information. The CL table contains a logical record for each antenna in the array at each CL time stamp. The CL time stamps are set by the user when loading the data. The default for VLA data is every 5 minutes. For VLBI data, it is every 1 minute. Each CL logical record requires

{15+ [14 × (# IF s)× (# pols)]} × 4bytes
For a 12-hour observation with the VLA with 2 IFs and 4 polarization pairs, with entries every 5 minutes, the CL table will occupy about
[ (12-×-60)- ] {15+ [14× 2× 2]}× 4× 5 × 27 bytes = 1.05M bytes

Since most other files are considerably smaller, their sizes can be ignored. That they exist and may require some disk, should not be forgotten. To look at the full AIPS disk usage on your computer in summary form:

> TASK ’DISKU’ ; INP  C R

to review the inputs.

> INDISK 0 ; DETIME 0  C R

to look at all disks and all data sets

> USERID 32000  C R

to look at all user numbers.

> DOALL FALSE ; GO  C R

to run the task in a summary mode.

Then to look at file sizes in detail:

> INDISK n ; USERID 0  C R

to restrict the display to your data sets and one disk.

> DOALL TRUE ; GO  C R

to run the task to list all files on disk n.

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