Some Examples of using ATLOD

In the following examples, any adverb that is not listed should be set to zero (for numeric adverbs) or an obvious default (such as bcount = 1 for first scan to load) or blank (for string adverbs). ATLOD is of course activated with the GO ATLOD command.

1. Extract from 10 files on tape drive number 2 the and values for all frequencies and sources to text files in the DATA/FITS areas. These files will be called XYPHS_UID, TSYSX_UID, and TSYSY_UID where UID is your AIPS user number.

   intape=2 Load data from tape drive 2

   nfiles=10 Load 10 files

   optype='sysc' Extract SYSCAL infomration

   You can then plot the contents of these text files with the utility program pltsys. Just enter pltsys from the Unix command level and answer the questions. It can select frequencies so you can just load them all with ATLOD. It plots on a PGPLOT device.

2. Load 3 files from tape drive number 1 starting at the second file with sampler corrections activated. The three RPFITS files are all put into the same output AIPS file by ATLOD.

   intape=1 Load data from tape drive 1

   nskip=1 Begin loading at the second file

   nfiles=3 Load 3 files

   outname='zeeman' Specify output file or default

   outclass='uv' is source name. When appending

   outseq=1 data, must specify fully

   outdisk=3 Choose local disk with most space

   optype='load' Load the data

   ifmap=-1 Allow ATLOD to arrange IF axis

   douvcomp=-1 No data compression

   aparm(1)=-1 Leave as linear polarizations but call them circulars

   cparm(6)=4 Correct data with bad sampler statistics

3. Load a file from disk, appending to an existing AIPS file, and activate sampler corrections and flagging. The values in the xyphase array should be found from plotting up the text files generated with the optype='sysc' option (see example 1 above). In addition, by examining these plots, it was determined that any point more than 10 degrees from the mean is bad and these data are dropped. Finally, it is assumed that there are two IFs in these data.

   infile='myarea:bigfile' Specify disk file

   outname='1934-638' Specify existing

   outclass='uv' file for appending outseq=1 outdisk=4

   optype='load' Load the data

   ifmap=-1 Allow ATLOD to arrange IF axis

   douvcomp=-1 No data compression

   aparm(1)=-1 Label linear polarizations as circular aparm(10)=-10 from values in xyphase by 10 degrees

   cparm(4)=1 Tell ATLOD to look in xyphase array

   cparm(6)=4 Correct data with bad sampler statistics xyphase=-5.0,10.2,3.4,-0.2,1.2,12.3, -2.1,0.3,-10.2,8.9,5.4,-4.7

4. Consider an observation where the first IF has been set to observe in 4-MHz, 513-channel, 2-polarization mode and IF 2 has been set to observe in 128-MHz, 33-channel, 4-polarization mode. These two IFs cannot go into the same AIPS file because they have different numbers of polarizations and different numbers of channels. Thus, you must make two passes with ATLOD, selecting the two IFs separately. In the following example, we select just the 8 MHz data (IF 1), reading 5 files from tape drive number 1, activating sampler corrections, data compression, Hanning smoothing and dropping every other channel. ATLOD is allowed to choose the name of the output file.

   intape=1 Read from tape drive number 1

   nfiles=5 Read five files

   outdisk=4 Specify local output disk

   optype='load' Load the data

   ifmap=-1 Allow ATLOD to arrange IF axis

   ifsel=1 Select IF 1 only

   chansel=1,513,2 Select every other channel after Hanning

   douvcomp=1 Activate data compression

   aparm(1)=-1 Leave as linear polarizations but call them circulars

   cparm(6)=4 Correct data with bad sampler statistics

   dparm(2)=1 Hanning smooth spectra

              

5. The AIPS verb UCAT will show the new file in the AIPS\ directory (termed a catalogue). Now, use the verb GETNAME to select the new file (e.g. GETNAME 1 to get the file located in catalogue slot 1 on the current indisk), and examine its header with the command IMHEAD. After the header information, you should see that there are five extension files associated with the multi-source file (see Appendix C for descriptions of the types of extension files you will encounter). There must be an antenna (AN) file, an SU (source) table, and an FQ (frequency) table. Never delete these three tables, as there is no simple way to regenerate them short of re-running ATLOD. You should also see the index (NX) and initial calibration (CL) tables. If the NX and CL tables are not present, probably your data were not loaded in time order and need to be sorted. ATLOD should have informed you if this was the case. The NX and CL tables can then be created with INDXR (see § 5).
6. Most of the messages that ATLOD writes to the terminal also get put into the history file for inspection at your leisure.