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Starting Out With AIPS Tutorial
James M Anderson
This tutorial session is intended to get people familiar with the basic concepts of radio interferometry. The student will be introduced to interferometry data, visibilities, the (u,v) plane, calibration, and imaging.
Step 1 --- Figure Out What to Observe (Reduce)
I decided to try to make an image of the Sun, as the Solar KSP is a significant part of GLOW. The NRAO image archive has a nice image of the Sun at 1400 MHz located at http://images.nrao.edu/8
Image courtesy of NRAO/AUI
Let's try to reduce the data ourselves.
Step 2 --- Download the Data From the Archive
Conveniently, the NRAO image archive gives details about the observations used to make the image, so I downloaded the data from the NRAO data archive, making sure to select the “AIPS friendly” filename option.
This has resulted in two files on my hard drive in my current directory:
ls -l
total 54164
-rw-r—– 1 anderson zeall 21002240 2008-11-11 14:40 GD_1
-rw-r—– 1 anderson zeall 34392064 2008-11-11 14:41 GD_2
Step 3 --- Start up AIPS
aips
I have chosen to use user ID 100, at semi-random selection.
At first, most of the archane syntax used to enter commands to AIPS will be difficult. As this is a tutorial session which intends to teach you about radio interferometry, and not how to use AIPS, we will gloss over the technical challenges of interacting with AIPS.
In AIPS you the user interact with something called POPS. You give POPS information by setting variables called ADVERBS to specific values. You can tell POPS which TASK you plan to run by setting a TASK ADVERB. If you want to check the values of ADVERBs for the current TASK, you ask for INPUTS. Because POPS will try to figure out what you mean if you only input the first few letters of an ADVERB or VERB, you can often abbreviate this to just INP. Also note that since AIPS is case-insensitive by default, you could also just type inp. If you want help on a specific topic, ask for HELP. If you want even more explanation for something, say EXPLAIN. If you don't know what it is you are trying to do, but you have some vague notion, say APROPOS SOMETHING. Note that apostrophes, and in certain locations, the lack of an apostrophe are significant.
Step 4 --- Initial look at data
FILLM
The AIPS task to read raw VLA data into AIPS is called FILLM.
dowait=true
task 'fillm'
default
datain = 'PWD:GD_
nfiles=0
ncount=2
vlamode='S '
doweight=10
doconcat=true
douvcomp=0
cparm(2)=16
cparm(4)=28
cparm(8)=10./60
go
This sets us up to read the data, sets the VLA mode to Solar, tells AIPS not to change the source if the position appears to be moving (which the Sun does), sets the shadowing limit to 28 meters, and sets the CL table interval to 10 seconds.
LISTR --- scan listing
First, let's check out which file we need.
pcat
AIPS 1: Catalog on disk 1 AIPS 1: Cat Usid Mapname Class Seq Pt Last access Stat AIPS 1: 1 100 19810926 .C BAND. 1 UV 11-NOV-2008 18:44:06 AIPS 1: 2 100 19810926 .L BAND. 1 UV 11-NOV-2008 18:46:44 AIPS 1: 3 100 19810926 .C BAND. 2 UV 11-NOV-2008 18:40:21 AIPS 1: 4 100 19810926 .L BAND. 2 UV 11-NOV-2008 18:40:21
default listr
task 'listr'
indi 1
getn 2
optype 'scan'
docrt=132
go
AIPS 1: Got(1) disk= 1 user= 100 type=UV 19810926.L BAND.1 vlb054 LISTR(31DEC08) 100 11-NOV-2008 18:46:44 Page 1 File = 19810926 .L BAND. 1 Vol = 1 Userid = 100 Freq = 1.446150006 GHz Ncor = 4 No. vis = 278465 Scan summary listing Scan Source Qual Calcode Sub Timerange FrqID START VIS END VIS 1 1148-001 : 0000 C 1 0/13:53:25 - 0/13:54:35 1 1 2195 2 SUN : 0000 1 0/13:59:15 - 0/13:59:35 1 2196 3150 3 1148-001 : 0000 C 1 0/14:18:05 - 0/14:19:35 1 3151 5809 4 SUN : 0000 1 0/14:20:25 - 0/14:24:35 1 5810 14662 5 1148-001 : 0000 C 1 0/14:43:05 - 0/14:44:35 1 14663 17320 6 SUN : 0000 1 0/14:45:25 - 0/14:49:35 1 17321 25867 7 1148-001 : 0000 C 1 0/15:07:55 - 0/15:09:25 1 25868 28503 8 SUN : 0000 1 0/15:10:15 - 0/15:14:25 1 28504 37058 9 1148-001 : 0000 C 1 0/15:32:55 - 0/15:34:25 1 37059 39716 10 SUN : 0000 1 0/15:35:15 - 0/15:39:25 1 39717 48338 11 1148-001 : 0000 C 1 0/15:57:55 - 0/15:59:25 1 48339 50720 12 SUN : 0000 1 0/16:00:15 - 0/16:04:15 1 50721 58994 13 1148-001 : 0000 C 1 0/16:22:45 - 0/16:24:15 1 58995 61584 14 SUN : 0000 1 0/16:25:05 - 0/16:29:15 1 61585 70334 15 1148-001 : 0000 C 1 0/16:47:45 - 0/16:49:15 1 70335 72949 16 SUN : 0000 1 0/16:50:05 - 0/16:54:15 1 72950 81664 17 1148-001 : 0000 C 1 0/17:12:35 - 0/17:12:35 1 81665 81664 18 1148-001 : 0000 C 1 0/17:12:45 - 0/17:14:05 1 81665 84070 19 SUN : 0000 1 0/17:14:55 - 0/17:19:05 1 84071 92937 20 1148-001 : 0000 C 1 0/17:37:35 - 0/17:39:05 1 92938 95507 21 SUN : 0000 1 0/17:39:45 - 0/17:44:25 1 95508 105079 22 1148-001 : 0000 C 1 0/18:02:25 - 0/18:03:55 1 105080 107535 23 SUN : 0000 1 0/18:04:45 - 0/18:08:55 1 107536 116401 24 1148-001 : 0000 C 1 0/18:27:25 - 0/18:28:55 1 116402 119012 25 SUN : 0000 1 0/18:29:45 - 0/18:33:55 1 119013 127842 26 1148-001 : 0000 C 1 0/18:52:35 - 0/18:53:55 1 127843 129825 27 SUN : 0000 1 0/18:54:45 - 0/18:59:05 1 129826 137705 28 1148-001 : 0000 C 1 0/19:17:25 - 0/19:18:45 1 137706 139972 29 SUN : 0000 1 0/19:19:35 - 0/19:23:45 1 139973 148118 30 1148-001 : 0000 C 1 0/19:42:15 - 0/19:43:45 1 148119 150467 31 SUN : 0000 1 0/19:44:35 - 0/19:53:05 1 150468 168022 32 1148-001 : 0000 C 1 0/20:07:05 - 0/20:08:35 1 168023 170342 33 SUN : 0000 1 0/20:09:25 - 0/20:13:35 1 170343 178889 34 1148-001 : 0000 C 1 0/20:32:05 - 0/20:33:35 1 178890 181422 35 SUN : 0000 1 0/20:34:25 - 0/20:38:35 1 181423 190047 36 1148-001 : 0000 C 1 0/20:57:05 - 0/20:58:35 1 190048 192547 37 SUN : 0000 1 0/20:59:25 - 0/21:03:35 1 192548 201271 38 1148-001 : 0000 C 1 0/21:21:55 - 0/21:23:25 1 201272 203709 39 SUN : 0000 1 0/21:24:15 - 0/21:28:25 1 203710 212708 40 1148-001 : 0000 C 1 0/21:47:05 - 0/21:48:25 1 212709 215193 41 SUN : 0000 1 0/21:49:15 - 0/21:53:25 1 215194 224112 42 1148-001 : 0000 C 1 0/22:11:45 - 0/22:13:15 1 224113 226323 43 SUN : 0000 1 0/22:14:05 - 0/22:18:15 1 226324 234634 44 1148-001 : 0000 C 1 0/22:36:55 - 0/22:38:15 1 234635 236916 45 SUN : 0000 1 0/22:39:05 - 0/22:43:15 1 236917 245740 46 1148-001 : 0000 C 1 0/23:01:55 - 0/23:03:15 1 245741 248122 47 SUN : 0000 1 0/23:04:05 - 0/23:08:05 1 248123 256112 48 1148-001 : 0000 C 1 0/23:26:45 - 0/23:28:05 1 256113 258141 49 SUN : 0000 1 0/23:28:55 - 0/23:33:05 1 258142 265941 50 1148-001 : 0000 C 1 0/23:51:45 - 0/23:53:05 1 265942 267662 51 SUN : 0000 1 0/23:54:05 - 0/23:58:05 1 267663 275388 52 SUN : 0000 1 1/00:07:25 - 1/00:07:55 1 275389 276069 53 3C286 : 0000 B 1 1/00:21:35 - 1/00:22:55 1 276070 278465 Source summary Velocity type = ' ' Definition = ' ' ID Source Qual Calcode RA( 0.0) Dec( 0.0) IFlux QFlux UFlux VFlux No. vis 1 1148-001 : 0000 C 11:48:10.1300 -00:07:13.300 0.000 0.000 0.000 0.000 59936 2 SUN : 0000 12:10:30.1272 -01:08:22.648 0.000 0.000 0.000 0.000 216133 3 3C286 : 0000 B 13:28:49.6570 30:45:58.640 0.000 0.000 0.000 0.000 2396 ID Source Freq(GHz) Velocity(Km/s) Rest freq (GHz) 1 All Sources 1.4462 0.0000 0.0000 Frequency Table summary FQID IF# Freq(GHz) BW(kHz) Ch.Sep(kHz) Sideband 1 1 1.44615001 12500.0010 12500.0010 1 AIPS 1: Resumes
getn 4
go
AIPS 1: Got(1) disk= 1 user= 100 type=UV 19810926.L BAND.2 vlb054 LISTR(31DEC08) 100 11-NOV-2008 18:49:17 Page 1 File = 19810926 .L BAND. 2 Vol = 1 Userid = 100 Freq = 1.446150006 GHz Ncor = 4 No. vis = 207072 Scan summary listing Scan Source Qual Calcode Sub Timerange FrqID START VIS END VIS 1 SUN : 0000 1 0/14:05:15 - 0/14:09:35 1 1 8935 2 SUN : 0000 1 0/14:30:05 - 0/14:34:35 1 8936 17885 3 SUN : 0000 1 0/14:55:05 - 0/14:59:25 1 17886 26458 4 SUN : 0000 1 0/15:19:55 - 0/15:24:25 1 26459 35408 5 SUN : 0000 1 0/15:44:55 - 0/15:49:25 1 35409 44108 6 SUN : 0000 1 0/16:09:45 - 0/16:14:15 1 44109 52834 7 SUN : 0000 1 0/16:34:45 - 0/16:39:15 1 52835 61669 8 SUN : 0000 1 0/16:59:45 - 0/17:04:05 1 61670 70226 9 SUN : 0000 1 0/17:24:35 - 0/17:29:05 1 70227 79180 10 SUN : 0000 1 0/17:50:15 - 0/17:54:05 1 79181 86877 11 SUN : 0000 1 0/18:14:25 - 0/18:18:55 1 86878 95785 12 SUN : 0000 1 0/18:39:35 - 0/18:44:05 1 95786 104689 13 SUN : 0000 1 0/19:04:25 - 0/19:08:45 1 104690 112638 14 SUN : 0000 1 0/19:29:15 - 0/19:33:45 1 112639 120854 15 SUN : 0000 1 0/19:54:25 - 0/19:58:45 1 120855 128861 16 SUN : 0000 1 0/20:19:05 - 0/20:23:35 1 128862 137749 17 SUN : 0000 1 0/20:44:05 - 0/20:48:35 1 137750 146600 18 SUN : 0000 1 0/21:08:55 - 0/21:13:25 1 146601 155488 19 SUN : 0000 1 0/21:33:55 - 0/21:38:25 1 155489 164306 20 SUN : 0000 1 0/21:58:55 - 0/22:03:25 1 164307 173005 21 SUN : 0000 1 0/22:23:55 - 0/22:28:15 1 173006 181479 22 SUN : 0000 1 0/22:48:55 - 0/22:53:25 1 181480 190299 23 SUN : 0000 1 0/23:13:45 - 0/23:18:05 1 190300 199102 24 SUN : 0000 1 0/23:38:45 - 0/23:43:05 1 199103 207072 25 SUN : 0000 1 1/00:01:15 - 1/00:01:15 1 207073 207072 Source summary Velocity type = ' ' Definition = ' ' ID Source Qual Calcode RA( 0.0) Dec( 0.0) IFlux QFlux UFlux VFlux No. vis 1 SUN : 0000 12:10:30.1272 -01:08:22.648 0.000 0.000 0.000 0.000 207072 ID Source Freq(GHz) Velocity(Km/s) Rest freq (GHz) 1 All Sources 1.4462 0.0000 0.0000 Frequency Table summary FQID IF# Freq(GHz) BW(kHz) Ch.Sep(kHz) Sideband 1 1 1.44615001 12500.0010 12500.0010 1 AIPS 1: Resumes