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.
History: 2008 Nov ?? Initial version 2010 NOv 14 Update for 31DEC10 AIPS
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
You should be able to download them from GD_1 and GD_2.
While you are there, grab the new set of commands from Sun.txt.
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.
dowait=true
dohist=1
docrt=132
dotv=1
Step 4 --- Initial look at data
FILLM
The AIPS task to read raw VLA data into AIPS is called FILLM.
task 'fillm'
datain = 'PWD:GD_
nfiles=0
ncount=2
vlamode='S '
band 'l'
doweight=10
doconcat=true
douvcomp=0
cparm(2)=16
cparm(4)=28
cparm(8)=10./60
dparm 0
bparm 0
timer 0
calcode ' '
clron
outdisk 1
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.
Header information
indisk 1
pcat
AIPS 1: Catalog on disk 1 AIPS 1: Cat Usid Mapname Class Seq Pt Last access Stat AIPS 1: 1 100 19810926 .L BAND. 1 UV 14-NOV-2008 21:35:31
getn 1
imhe
AIPS 1: Image=MULTI (UV) Filename=19810926 .L BAND. 1 AIPS 1: Telescope=VLA Receiver=VLA AIPS 1: Observer=GD User #= 100 AIPS 1: Observ. date=26-SEP-1981 Map date=14-NOV-2008 AIPS 1: # visibilities 556884 Sort order TB AIPS 1: Rand axes: UU-L-SIN VV-L-SIN WW-L-SIN BASELINE TIME1 AIPS 1: SOURCE FREQSEL AIPS 1: ---------------------------------------------------------------- AIPS 1: Type Pixels Coord value at Pixel Coord incr Rotat AIPS 1: COMPLEX 3 1.0000000E+00 1.00 1.0000000E+00 0.00 AIPS 1: STOKES 4 -1.0000000E+00 1.00 -1.0000000E+00 0.00 AIPS 1: FREQ 1 1.4461500E+09 1.00 1.2500000E+07 0.00 AIPS 1: IF 1 1.0000000E+00 1.00 1.0000000E+00 0.00 AIPS 1: RA 1 00 00 00.000 1.00 3600.000 0.00 AIPS 1: DEC 1 00 00 00.000 1.00 3600.000 0.00 AIPS 1: ---------------------------------------------------------------- AIPS 1: Coordinate equinox 0.00 AIPS 1: Maximum version number of extension files of type HI is 1 AIPS 1: Maximum version number of extension files of type AN is 1 AIPS 1: Maximum version number of extension files of type NX is 1 AIPS 1: Maximum version number of extension files of type SU is 1 AIPS 1: Maximum version number of extension files of type FQ is 1 AIPS 1: Maximum version number of extension files of type CL is 1 AIPS 1: Maximum version number of extension files of type TY is 1 AIPS 1: Maximum version number of extension files of type WX is 1 AIPS 1: Maximum version number of extension files of type OF is 1 AIPS 1: Keyword = 'CORRMODE' value = ' ' AIPS 1: Keyword = 'VLAIFS ' value = 'AC ' AIPS 1: Keyword = 'CORRCOEF' value = -1
LISTR --- scan listing
task 'listr'
indi 1
getn 1
optype 'scan'
docrt=132
flagver 0
sources ' '
stokes ' '
docalib 0
gainuse 1
dopol -1
dparm 0
go
vlb054 LISTR(31DEC10) 100 21-OCT-2010 17:17:44 Page 1 File = 19810926 .L BAND. 1 Vol = 1 Userid = 100 Freq = 1.446150006 GHz Ncor = 4 No. vis = 421247 Scan summary listing Scan Source Qual Calcode Sub Timerange FrqID START VIS END VIS 1 1148-001 : 0000 C 1 0/13:53:25 - 0/13:53:25 1 1 0 2 1148-001 : 0000 C 1 0/13:53:35 - 0/13:54:35 1 1 1113 3 SUN : 0000 1 0/13:59:15 - 0/13:59:35 1 1114 1575 4 SUN : 0000 1 0/14:05:25 - 0/14:09:35 1 1576 5952 5 1148-001 : 0000 C 1 0/14:18:25 - 0/14:19:35 1 5953 7738 6 SUN : 0000 1 0/14:20:25 - 0/14:24:35 1 7739 12262 7 SUN : 0000 1 0/14:30:25 - 0/14:34:35 1 12263 17489 8 1148-001 : 0000 C 1 0/14:43:25 - 0/14:44:35 1 17490 19470 9 SUN : 0000 1 0/14:45:25 - 0/14:49:35 1 19471 25116 10 SUN : 0000 1 0/14:55:25 - 0/14:59:25 1 25117 30808 11 1148-001 : 0000 C 1 0/15:08:15 - 0/15:09:25 1 30809 32950 12 SUN : 0000 1 0/15:10:15 - 0/15:14:25 1 32951 39133 13 SUN : 0000 1 0/15:20:15 - 0/15:24:25 1 39134 45646 14 1148-001 : 0000 C 1 0/15:33:15 - 0/15:34:25 1 45647 47809 15 SUN : 0000 1 0/15:35:15 - 0/15:39:25 1 47810 54604 16 SUN : 0000 1 0/15:45:15 - 0/15:49:25 1 54605 61507 17 1148-001 : 0000 C 1 0/15:58:15 - 0/15:59:25 1 61508 63889 18 SUN : 0000 1 0/16:00:15 - 0/16:04:15 1 63890 70412 19 SUN : 0000 1 0/16:10:05 - 0/16:14:15 1 70413 77315 20 1148-001 : 0000 C 1 0/16:23:05 - 0/16:24:15 1 77316 79905 21 SUN : 0000 1 0/16:25:05 - 0/16:29:15 1 79906 88655 22 SUN : 0000 1 0/16:35:05 - 0/16:39:15 1 88656 97490 23 1148-001 : 0000 C 1 0/16:48:05 - 0/16:49:15 1 97491 100105 24 SUN : 0000 1 0/16:50:05 - 0/16:54:15 1 100106 108820 25 SUN : 0000 1 0/17:00:05 - 0/17:04:05 1 108821 117377 26 1148-001 : 0000 C 1 0/17:12:55 - 0/17:14:05 1 117378 119783 27 SUN : 0000 1 0/17:14:55 - 0/17:19:05 1 119784 128650 28 SUN : 0000 1 0/17:24:55 - 0/17:29:05 1 128651 137604 29 1148-001 : 0000 C 1 0/17:37:55 - 0/17:39:05 1 137605 140174 30 SUN : 0000 1 0/17:39:45 - 0/17:44:25 1 140175 149746 31 SUN : 0000 1 0/17:50:25 - 0/17:54:05 1 149747 157443 32 1148-001 : 0000 C 1 0/18:02:45 - 0/18:03:55 1 157444 159899 33 SUN : 0000 1 0/18:04:45 - 0/18:08:55 1 159900 168765 34 SUN : 0000 1 0/18:14:45 - 0/18:18:55 1 168766 177673 35 1148-001 : 0000 C 1 0/18:27:45 - 0/18:28:55 1 177674 180284 36 SUN : 0000 1 0/18:29:45 - 0/18:33:55 1 180285 189114 37 SUN : 0000 1 0/18:39:45 - 0/18:44:05 1 189115 198018 38 1148-001 : 0000 C 1 0/18:52:45 - 0/18:53:55 1 198019 200001 39 SUN : 0000 1 0/18:54:45 - 0/18:59:05 1 200002 207881 40 SUN : 0000 1 0/19:04:35 - 0/19:08:45 1 207882 215830 41 1148-001 : 0000 C 1 0/19:17:35 - 0/19:18:45 1 215831 218097 42 SUN : 0000 1 0/19:19:35 - 0/19:23:45 1 218098 226243 43 SUN : 0000 1 0/19:29:35 - 0/19:33:45 1 226244 234459 44 1148-001 : 0000 C 1 0/19:42:35 - 0/19:43:45 1 234460 236808 45 SUN : 0000 1 0/19:44:35 - 0/19:53:05 1 236809 254363 46 SUN : 0000 1 0/19:54:35 - 0/19:58:45 1 254364 262370 47 1148-001 : 0000 C 1 0/20:07:25 - 0/20:08:35 1 262371 264690 48 SUN : 0000 1 0/20:09:25 - 0/20:13:35 1 264691 273237 49 SUN : 0000 1 0/20:19:25 - 0/20:23:35 1 273238 282125 50 1148-001 : 0000 C 1 0/20:32:25 - 0/20:33:35 1 282126 284658 51 SUN : 0000 1 0/20:34:25 - 0/20:38:35 1 284659 293283 52 SUN : 0000 1 0/20:44:25 - 0/20:48:35 1 293284 302134 53 1148-001 : 0000 C 1 0/20:57:25 - 0/20:58:35 1 302135 304634 54 SUN : 0000 1 0/20:59:25 - 0/21:03:35 1 304635 313358 55 SUN : 0000 1 0/21:09:15 - 0/21:13:25 1 313359 322246 56 1148-001 : 0000 C 1 0/21:22:15 - 0/21:23:25 1 322247 324222 57 SUN : 0000 1 0/21:24:15 - 0/21:28:25 1 324223 333221 58 SUN : 0000 1 0/21:34:15 - 0/21:38:25 1 333222 341392 59 1148-001 : 0000 C 1 0/21:47:15 - 0/21:48:25 1 341393 343406 60 SUN : 0000 1 0/21:49:15 - 0/21:53:25 1 343407 350399 61 SUN : 0000 1 0/21:59:15 - 0/22:03:25 1 350400 357289 62 1148-001 : 0000 C 1 0/22:12:05 - 0/22:13:15 1 357290 359048 63 SUN : 0000 1 0/22:14:05 - 0/22:18:15 1 359049 365542 64 SUN : 0000 1 0/22:24:05 - 0/22:28:15 1 365543 372227 65 1148-001 : 0000 C 1 0/22:37:05 - 0/22:38:15 1 372228 373947 66 SUN : 0000 1 0/22:39:05 - 0/22:43:15 1 373948 380876 67 SUN : 0000 1 0/22:49:05 - 0/22:53:25 1 380877 387324 68 1148-001 : 0000 C 1 0/23:02:05 - 0/23:03:15 1 387325 388927 69 SUN : 0000 1 0/23:04:05 - 0/23:08:05 1 388928 394642 70 SUN : 0000 1 0/23:13:55 - 0/23:18:05 1 394643 401050 71 1148-001 : 0000 C 1 0/23:26:55 - 0/23:28:05 1 401051 402397 72 SUN : 0000 1 0/23:28:55 - 0/23:33:05 1 402398 407527 73 SUN : 0000 1 0/23:38:55 - 0/23:43:05 1 407528 412709 74 1148-001 : 0000 C 1 0/23:51:55 - 0/23:53:05 1 412710 413612 75 SUN : 0000 1 0/23:54:05 - 0/23:58:05 1 413613 418616 76 SUN : 0000 1 1/00:07:35 - 1/00:07:55 1 418617 419028 77 3C286 : 0000 B 1 1/00:21:45 - 1/00:22:55 1 419029 421247 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 52089 2 SUN : 0000 12:10:30.1272 -01:08:22.648 0.000 0.000 0.000 0.000 366939 3 3C286 : 0000 B 13:28:49.6570 30:45:58.640 0.000 0.000 0.000 0.000 2219 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
PRTAN
Print the Antenna positions — useful for thinking about calibration.
go prtan
vlb054 PRTAN(31DEC08) 100 14-NOV-2008 21:45:10 Page 1
File=19810926 .L BAND. 1 An.ver= 1 Vol= 1 User= 100
Array= VLA Freq= 1446.150006 MHz Ref.date= 26-SEP-1981
Array reference position in meters (Earth centered)
Array BX= -1601185.36500 BY= -5041977.54700 BZ= 3554875.87000
Polar X = 0.00000 Polar Y = 0.00000 arcsec
Earth rotation rate = 360.9856449713 degrees / IAT day
GST at UT=0 = 364.7139688925 degrees
UT1-UTC= 0.0000000 Data time(IAT )-UTC= 0.0000000 seconds
Solutions not yet determined for a particular FREQID
Ant 1 = VLA:_N2 BX= -30.0602 BY= -4.7835 BZ= 45.7022
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 2 = VLA:_E5 BX= 51.8719 BY= 195.8466 BZ= -75.1013
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 3 = VLA:_E9 BX= 139.6430 BY= 536.8956 BZ= -207.7424
Mount=ALAZ Axis offset= -0.0033 meters IFA IFB
Feed polarization type = R L
Ant 4 = VLA:_E6 BX= 70.6548 BY= 267.7575 BZ= -102.8996
Mount=ALAZ Axis offset= 0.0078 meters IFA IFB
Feed polarization type = R L
Ant 5 = VLA:_N3 BX= -52.4373 BY= -8.2629 BZ= 78.6643
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 6 = VLA:_W2 BX= 14.7735 BY= -37.1404 BZ= -20.2135
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 7 = VLA:_W3 BX= 28.9195 BY= -74.4876 BZ= -41.0524
Mount=ALAZ Axis offset= -0.0036 meters IFA IFB
Feed polarization type = R L
Ant 8 = VLA:_W1 BX= 22.9920 BY= 3.4974 BZ= -32.4864
Mount=ALAZ Axis offset= 0.0084 meters IFA IFB
Feed polarization type = R L
Ant 9 = VLA:_E2 BX= 11.3328 BY= 40.6638 BZ= -15.1624
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 10 = VLA:_OUT BX= 0.0000 BY= 0.0000 BZ= 0.0000
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 11 = VLA:_E8 BX= 114.4257 BY= 438.6941 BZ= -169.4880
Mount=ALAZ Axis offset= 0.0048 meters IFA IFB
Feed polarization type = R L
Ant 12 = VLA:_E3 BX= 21.9945 BY= 81.5250 BZ= -30.9498
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 13 = VLA:_E7 BX= 91.5227 BY= 348.8871 BZ= -134.4449
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 14 = VLA:_W7 BX= 121.6261 BY= -319.1264 BZ= -177.5842
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 15 = VLA:_W9 BX= 186.8061 BY= -491.1158 BZ= -273.5624
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 16 = VLA:_E4 BX= 35.6150 BY= 133.6310 BZ= -51.1099
Mount=ALAZ Axis offset= -0.0051 meters IFA IFB
Feed polarization type = R L
Ant 17 = VLA:_W8 BX= 152.7524 BY= -401.2839 BZ= -223.4146
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 18 = VLA:_E1 BX= 45.3386 BY= 7.0026 BZ= -65.4888
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 19 = VLA:_N7 BX= -193.6105 BY= -30.2503 BZ= 286.4580
Mount=ALAZ Axis offset= -0.0030 meters IFA IFB
Feed polarization type = R L
Ant 20 = VLA:_N1 BX= 0.6703 BY= 0.0144 BZ= 0.5135
Mount=ALAZ Axis offset= 0.0045 meters IFA IFB
Feed polarization type = R L
Ant 21 = VLA:_N8 BX= -243.6039 BY= -38.0389 BZ= 360.0340
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 22 = VLA:_W5 BX= 68.6012 BY= -179.2282 BZ= -99.5242
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 23 = VLA:_N5 BX= -108.4301 BY= -16.9862 BZ= 161.0152
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 24 = VLA:_N9 BX= -298.3837 BY= -46.5620 BZ= 440.6260
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 25 = VLA:_N6 BX= -148.4545 BY= -23.2162 BZ= 219.9871
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 26 = VLA:_N4 BX= -74.8318 BY= -11.7331 BZ= 111.6208
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 27 = VLA:_W6 BX= 93.5170 BY= -245.0012 BZ= -136.2284
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 28 = VLA:_W4 BX= 46.9220 BY= -122.0267 BZ= -67.6047
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Ant 29 = VPT:_OUT BX= 0.0000 BY= 0.0000 BZ= 0.0000
Mount=ALAZ Axis offset= 0.0000 meters IFA IFB
Feed polarization type = R L
Location Of VLA Antennas
N9 (24)
N8 (21)
N7 (19)
N6 (25)
N5 (23)
N4 (26)
N3 ( 5)
N2 ( 1)
N1 (20)
( 8) W1 E1 (18)
( 6) W2 E2 ( 9)
( 7) W3 E3 (12)
(28) W4 E4 (16)
(22) W5 E5 ( 2)
(27) W6 E6 ( 4)
(14) W7 E7 (13)
(17) W8 E8 (11)
(15) W9 E9 ( 3)
VLA:_OUT (10)
VPT:_OUT (29)
AIPS 1: Resumes
The really important part for you, the data reducer, is the antenna layout at the bottom. This tells you in a nice graphical form where each antenna is located. This helps you to figure out which baselines are small, and which baselines are long. This is also useful for figuring out other things related to antenna position and baseline direction.
UVPLT
Let's have a look at the information about the visibilities.
task 'uvplt'
source '3c286',' '
stokes 'half'
calcode ' '
uvrange 0
antennas 0
basel 0
xinc 1
aparm 0
bparm 0
doweight 1
refant 3
do3col 1
dotv 1
tvinit
go
source '1148-001', ' '
go
Warning: the next step will take a long time. You are free to skip this, and just look at the picture.
source 'sun',' '
go
source '3c286',' '
bparm 0 2
go
source '1148-001', ' '
go
source '3c286',' '
bparm 11 1
go
source '1148-001', ' '
go
source '3c286',' '
bparm 6 7
go
source '1148-001', ' '
go
source ' '
bparm 11 15
xinc 50
go
bparm 11 18
go
LISTR
Now let's look at the raw visibility numbers.
xinc 1
task 'listr'
optype 'list'
source '3c286', ' '
stokes ' '
bif 0
eif 0
flagver 0
dparm 0
antenna 3,0
go
vlb054 LISTR(31DEC08) 100 14-NOV-2008 22:05:45 Page 1 File = 19810926 .L BAND. 1 Vol = 1 Userid = 100 Channels = 1- 1 IF = 1 Freq= 1.446150006 GHz Ncor= 1 No. vis= 3159 Stokes = RR Subarray = 1 Source=3C286 : 0000, Stokes=RR , IF= 1, Chans= 1- 1 Flux = 0.0000 Jy, Calcode = B , Freq = 1.446150006 GHz Amplitudes, 1000 = 1.000 Jy, averging type = Vector Baselines 1 3 2 3 3 4 3 5 3 6 3 7 3 8 3 9 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 1/00:21:35 293 259 258 282 45 360 431 333 563 326 247 264 256 469 287 127 283 84 56 455 12 344 307 313 321 347 Amplitudes, 1000 = 10.000 Jy, averging type = Vector 1/00:21:45 195 180 182 168 15 212 234 203 247 135 160 177 169 187 174 156 178 129 66 205 1 185 186 189 158 158 1/00:21:55 206 196 194 176 67 223 246 214 252 139 169 192 183 193 183 185 190 188 205 214 1 192 199 199 165 168 1/00:22:05 209 197 197 179 165 223 246 217 251 144 172 193 185 194 186 186 193 190 235 216 1 193 201 202 167 169 1/00:22:15 205 194 196 178 198 223 244 214 246 140 170 189 182 193 183 186 190 190 235 212 0 193 198 199 164 169 1/00:22:25 206 192 197 177 196 222 243 214 242 139 165 189 180 193 183 184 190 186 231 212 1 191 197 199 164 168 1/00:22:35 207 195 196 178 198 223 246 215 240 140 166 192 182 192 184 185 190 190 233 214 0 192 199 199 165 168 1/00:22:45 206 192 192 177 199 222 243 213 232 141 168 191 183 190 183 185 191 187 233 214 1 191 197 198 164 169 1/00:22:55 206 193 195 179 199 223 243 213 230 140 170 190 182 193 183 185 190 186 233 215 1 191 197 199 164 169 AIPS 1: Resumes
Flagging
Just enter these commands. We can talk later about why they needed to be applied.
task 'uvflg'
antenna 23,0
basel 0
timer 0
aparm 0
opcode 'flag'
reason 'bad ant'
dohist 1
go
antenna 26,0
timer 0 18 29 0 0 20 7 20
go
timer 0 0 0 0 0 15 8 10
go
timer 0 21 48 30 0 22 37 10
go
antenna 25,0
timer 0 22 38 20 1 0 21 50
go
More LISTR, now on the phase calibrator
task 'listr'
optype 'list'
source '1148-001', ' '
stokes ' '
calcode ' '
bif 0
eif 0
timer 0
flagver 0
dparm 0
antenna 3,0
go
vlb054 LISTR(31DEC08) 100 14-NOV-2008 22:35:27 Page 1 File = 19810926 .L BAND. 1 Vol = 1 Userid = 100 Channels = 1- 1 IF = 1 Freq= 1.446150006 GHz Ncor= 1 No. vis= 84072 Stokes = RR Subarray = 1 Applying flag table 1 Source=1148-001 : 0000, Stokes=RR , IF= 1, Chans= 1- 1 Flux = 0.0000 Jy, Calcode = C , Freq = 1.446150006 GHz Amplitudes, 1000 = 10.000 Jy, averging type = Vector Baselines 1 3 2 3 3 4 3 5 3 6 3 7 3 8 3 9 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 0/13:53:55 57 126 58 53 86 123 73 195 32 57 13 23 66 30 36 27 75 30 89 24 20 28 45 103 0/13:54:05 67 134 66 24 65 155 47 213 26 66 28 28 92 30 53 35 60 26 63 28 33 55 77 103 0/13:54:15 43 124 77 29 43 26 144 44 184 36 77 40 29 96 19 39 29 34 31 34 26 34 76 62 134 0/13:54:25 6 104 91 62 40 68 96 73 177 59 93 30 30 87 35 4 26 41 45 78 32 31 74 14 139 0/13:54:35 28 84 94 70 21 93 69 80 191 56 104 19 31 61 34 50 31 68 42 94 31 24 41 46 99 Source=1148-001 : 0000, Stokes=RR , IF= 1, Chans= 1- 1 Flux = 0.0000 Jy, Calcode = C , Freq = 1.446150006 GHz Amplitudes, 1000 = 10.000 Jy, averging type = Vector Baselines 1 3 2 3 3 4 3 5 3 6 3 7 3 8 3 9 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 0/14:18:25 37 65 58 31 101 107 83 230 68 57 35 34 81 33 90 40 56 18 32 32 45 69 32 47 0/14:18:35 4 65 55 22 78 85 80 191 67 58 28 28 78 26 58 28 58 33 50 29 39 28 17 39 0/14:18:45 36 62 56 30 17 32 45 47 128 48 57 28 32 61 32 48 24 31 44 48 34 26 18 29 17 0/14:18:55 54 54 70 40 24 39 15 18 194 27 61 30 36 28 33 80 34 6 45 27 34 25 52 36 35 0/14:19:05 48 27 87 54 30 90 70 24 176 21 56 29 47 14 39 114 42 29 50 42 43 44 63 24 47 0/14:19:15 38 7 105 40 33 117 116 67 113 59 63 42 43 51 44 105 45 70 51 62 44 58 66 29 39 0/14:19:25 23 48 112 35 30 75 117 92 198 80 50 46 44 84 46 57 38 74 59 63 47 48 21 50 30 0/14:19:35 58 72 99 36 26 39 70 66 123 60 31 38 40 86 34 35 41 42 49 31 42 27 33 46 35 Source=1148-001 : 0000, Stokes=RR , IF= 1, Chans= 1- 1 Flux = 0.0000 Jy, Calcode = C , Freq = 1.446150006 GHz Amplitudes, 1000 = 10.000 Jy, averging type = Vector Baselines 1 3 2 3 3 4 3 5 3 6 3 7 3 8 3 9 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 0/14:43:25 32 32 95 40 47 27 55 237 14 83 30 33 58 31 33 38 40 20 35 34 35 13 28 35 0/14:43:35 34 56 91 30 44 48 60 173 29 80 34 33 46 32 29 36 38 35 37 34 33 38 29 37 0/14:43:45 27 59 103 14 27 21 51 54 130 51 66 25 25 72 24 23 22 14 27 26 21 23 48 23 26 0/14:43:55 22 49 112 29 24 18 35 23 182 49 43 19 26 95 23 30 20 9 30 28 27 22 32 20 21 0/14:44:05 39 59 141 41 28 42 36 2 163 35 32 32 33 112 31 32 37 35 41 35 34 35 29 30 30 0/14:44:15 36 49 157 37 23 50 28 29 179 16 17 31 32 98 32 31 38 44 36 34 29 33 18 28 35 0/14:44:25 27 28 159 25 22 37 38 54 200 17 17 30 29 71 28 26 27 38 33 31 27 28 36 28 31 0/14:44:35 28 1 150 20 31 23 47 60 242 39 22 29 30 42 28 29 27 22 39 34 30 29 51 28 27 Source=1148-001 : 0000, Stokes=RR , IF= 1, Chans= 1- 1 Flux = 0.0000 Jy, Calcode = C , Freq = 1.446150006 GHz Amplitudes, 1000 = 10.000 Jy, averging type = Vector Baselines 1 3 2 3 3 4 3 5 3 6 3 7 3 8 3 9 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 0/15:08:15 17 35 52 25 33 42 35 148 14 29 28 29 49 29 31 30 27 15 38 29 32 35 25 33 0/15:08:25 29 38 64 22 27 33 32 146 14 38 27 25 52 25 31 33 18 29 30 27 22 23 22 35 0/15:08:35 33 25 70 27 23 25 27 25 135 25 35 21 25 49 21 29 26 17 30 25 24 19 18 18 29 0/15:08:45 50 35 91 34 35 42 44 43 185 32 52 37 34 49 34 34 30 38 45 40 36 39 43 33 33 0/15:08:55 30 28 84 30 32 37 43 34 188 26 53 32 33 26 32 26 29 42 37 40 32 36 41 27 26 0/15:09:05 21 27 72 28 31 37 46 35 185 26 56 31 32 9 31 27 37 36 37 39 32 30 35 29 35
dparm 1,0
go
vlb054 LISTR(31DEC08) 100 14-NOV-2008 22:36:24 Page 1 File = 19810926 .L BAND. 1 Vol = 1 Userid = 100 Channels = 1- 1 IF = 1 Freq= 1.446150006 GHz Ncor= 1 No. vis= 84072 Stokes = RR Subarray = 1 Applying flag table 1 Source=1148-001 : 0000, Stokes=RR , IF= 1, Chans= 1- 1 Flux = 0.0000 Jy, Calcode = C , Freq = 1.446150006 GHz Phase, 1000 = 1000.00 degrees, averging type = Vector Baselines 1 3 2 3 3 4 3 5 3 6 3 7 3 8 3 9 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 0/13:53:55 -154 176 177-145 82 59 -83 -35-118 -77 101 41 3 59 63 114 69 -97 80 76 88 -57 67 121 0/13:54:05 163 138-130 -83 141 119 -21 -20 -30 -50 52 43 52 78 97 122 122-106 147 78 88 46 166-137 0/13:54:15 127 100 -91 65-134-101 172 78 -173 44 -26 79 44 90 51 137 129-158-129 -79 72 102 95-124 -55 0/13:54:25 118 61 -61 125 -91 13-128 145 172 105 -3 99 45 126 51-125 122 -51-119 21 73 111 140 2 12 0/13:54:35 -125 9 -32 168 -49 68 -31-164 161 144 17 64 39 167 75 31 115 12-106 79 77 97-174 142 90 Source=1148-001 : 0000, Stokes=RR , IF= 1, Chans= 1- 1 Flux = 0.0000 Jy, Calcode = C , Freq = 1.446150006 GHz Phase, 1000 = 1000.00 degrees, averging type = Vector Baselines 1 3 2 3 3 4 3 5 3 6 3 7 3 8 3 9 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 0/14:18:25 135 174 69 167 66 121-173 51 109 26 75 39 58 61 136 118 27-117 30 73 88 140-157 -8 0/14:18:35 -72 153 124 160 123 168-128 93 145 32 67 42 93 49-154 126 72-128 56 67 111-158 177 13 0/14:18:45 -131 132 173 146-116-171-153 -91 147-177 42 68 36 129 50 -56 105 107-120 83 73 112 25 160 -43 0/14:18:55 -165 103-132 149-123 -19 -9 -18 6-122 55 73 40 167 61 23 101-175-110 89 76 81 66-175 -41 0/14:19:05 162 87 -88 160-120 46 81 143 -37 33 72 73 37 23 53 78 112 -3-118 46 73 83 112-159 -16 0/14:19:15 141 -86 -66 164-116 89 113 174 -114 69 87 66 40 22 49 120 122 26-126 54 73 98 143 165 -7 0/14:19:25 -137-143 -42 155-114 141 151-151 118 111 94 69 35 50 56 167 112 65-120 78 73 111 155 166 -18 0/14:19:35 -139-164 -20 142-130 -91-161-118 166 144 107 72 37 79 55 -66 99 109-114 88 78 99 37-168 -38 Source=1148-001 : 0000, Stokes=RR , IF= 1, Chans= 1- 1 Flux = 0.0000 Jy, Calcode = C , Freq = 1.446150006 GHz Phase, 1000 = 1000.00 degrees, averging type = Vector Baselines 1 3 2 3 3 4 3 5 3 6 3 7 3 8 3 9 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 0/14:43:25 -174-121 103 162 65 109 166 41 37 70 66 32-169 49 86 97 42-121 64 64 91 89-178 -29 0/14:43:35 -169-148 150 173 81 104-159 138 70 88 65 32 -85 48 76 109 66-129 60 67 92 71 178 -20 0/14:43:45 -165-171-168 150-127 97 120-123 116 107 114 64 28 -20 54 69 109 87-132 61 56 94 90 170 -18 0/14:43:55 -170 163-127 133-123 58 147 -84 90 142 139 68 35 32 53 74 91 6-133 61 58 85 121 175 -25 0/14:44:05 -177 139 -92 148-112 53 149 -32 72 177 164 69 35 70 47 82 97 19-127 64 64 90 134-174 -30 0/14:44:15 180 123 -62 162-122 68 116 147 62-116-143 65 32 105 54 81 109 35-124 64 66 90 87 175 -30 0/14:44:25 -176 101 -37 168-136 85 105 177 51 15 -85 66 30 145 50 76 112 59-132 57 64 88 72 171 -20 0/14:44:35 -162 105 -7 146-133 79 117-152 41 68 -46 68 30-163 47 71 96 67-132 61 59 87 97 173 -24 Source=1148-001 : 0000, Stokes=RR , IF= 1, Chans= 1- 1 Flux = 0.0000 Jy, Calcode = C , Freq = 1.446150006 GHz Phase, 1000 = 1000.00 degrees, averging type = Vector Baselines 1 3 2 3 3 4 3 5 3 6 3 7 3 8 3 9 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 0/15:08:15 -152 172-105 148 73 125-161 -32 127 -46 69 28 39 48 65 87 38-129 62 62 93 108 179 -40 0/15:08:25 -136 152 -86 139 76 126-157 -27 89 -36 66 28 63 53 80 95 41-139 66 61 96 114 175 -30 0/15:08:35 -164 140 -63 149-130 64 135-148 -15 107 -11 67 22 87 50 78 114 9-134 60 67 80 93 177 -17 0/15:08:45 178 144 -39 151-126 66 128-148 -3 119 9 68 28 106 51 90 108 12-127 58 65 82 91-177 -16 0/15:08:55 167 150 -18 151-124 70 124-149 9 132 23 69 27 121 48 70 87 27-127 57 62 87 101-179 -33 0/15:09:05 -160 162 3 151-129 72 126-157 21 135 33 65 28 74 51 48 93 40-134 67 61 96 111 177 -36
Calibration
SETJY
task 'setjy'
source '3c286',' '
optype 'calc'
aparm 0
aparm(2)=4
zerosp 0
go
vlb054> SETJY1: Task SETJY (release of 31DEC10) begins vlb054> SETJY1: **WARNING: OPCODE=CALC AND FREQID = -1 vlb054> SETJY1: FREQID WILL BE RESET TO 1, CHECK YOUR RESULTS CAREFULLY vlb054> SETJY1: A source model for this calibrator is available vlb054> SETJY1: Consult the help file for CALRD for assistance vlb054> SETJY1: / Flux calculated using known spectrum vlb054> SETJY1: BIF = 1 EIF = 1 /Range of IFs vlb054> SETJY1: '3C286 ' IF = 1 FLUX =14.6428 (Jy calcd) vlb054> SETJY1: / Using (1995.2) VLA or Reynolds (1934-638) coefficients vlb054> SETJY1: Appears to have ended successfully vlb054> SETJY1: vlb054 31DEC10 TST: Cpu= 0.0 Real= 0
CALRD
task 'calrd'
object '3c286'
band 'l'
go
vlb054> CALRD1: Task CALRD (release of 31DEC08) begins vlb054> CALRD1: Reading disk file AIPSTARS:3C286_L.MODEL vlb054> CALRD1: Create 3C286_L .MODEL . 1 (MA) on disk 1 cno 2 vlb054> CALRD1: Appears to have ended successfully vlb054> CALRD1: vlb054 31DEC08 TST: Cpu= 0.0 Real= 0
So it looks like the calibration data image was put into catalog entry number 2.
Let's have a look at it.
getn 2
tvinit
tvlod
tvfiddle
UVFIX
The sky positions (RA and Dec) were entered as coordinates of date, because the Sun is a moving object. However, they were entered in an odd fashion which means that the current software has trouble dealing with the calibration image for proper calibration. Run the fix program.
task 'uvfix'
getn 1
clron
shift 0
uvfixprm 0
go
UVFIX change in April means we have to regenerate NX table
task 'indxr'
getn 3
cparm 0
cparm(3)= -1
bparm 0
go
CALIB
First, we do the amplitude calibrator.
task 'calib'
getn 3
calsour '3c286',' '
uvrange 0
antennas 0
timer 0
refant 24
weightit 1
in2di 1
get2n 2
ncomp 0
solmode 'A&P'
aparm 0
aparm(6) 2
minamper 10
minphser 10
docalib 1
gainuse 1
solint 30
solsub 2
cparm 0
cparm(3) 10
cparm(4) 10
soltype ' '
clrmsg
go
clrmsg
Next, the phase calibrator.
calsour '1148-001',' '
clr2n
uvrange 1.5,0
solint 0
go
clrmsg
SNPLT
Look at the amplitude calibrator results.
task 'snplt'
source ' '
inver 1
inext 'sn'
stokes ' '
optype 'phas'
opcode 'alsi'
xinc 1
nplots 9
antenna 0
timer 0
tvinit
dotv 1
go
optype 'amp'
go
Look at the phase calibrator results.
inver 2
optype 'phas'
go
optype 'amp'
go
GETJY
Now we need to transfer the amplitude calibration information from the amplitude calibrator to the phase calibrator.
task 'getjy'
sources '1148-001',' '
calsour '3c286',' '
calcode ' '
bif 0
eif 0
antenna 0
timer 0
snver 0
go
vlb054> GETJY1: Task GETJY (release of 31DEC08) begins vlb054> GETJY1: Source:Qual CALCODE IF Flux (Jy) vlb054> GETJY1: 1148-001 : 0 C 1 2.90731 +/- 0.04192 vlb054> GETJY1: Appears to have ended successfully vlb054> GETJY1: vlb054 31DEC08 TST: Cpu= 0.0 Real= 0
2.9 Jy agrees relatively well with the rough value given by the VLA calibrator list.
1150-003 J2000 A 11h50m43.870761s -00d23'54.204900" Aug01 1148-001 B1950 A 11h48m10.124900s -00d07'13.164000" ----------------------------------------------------- BAND A B C D FLUX(Jy) UVMIN(kL) UVMAX(kL) ===================================================== 20cm L P P P P 2.80 visplot 6cm C P P P P 1.92 3.7cm X P P P P 1.25 visplot 2cm U P P P P 1.40 1.3cm K S S S S 0.63 visplot 0.7cm Q W W W W 0.65''
Redo the CALIB calibration for the phase calibrator
inext 'sn'
inver 2
extdest
tget calib
go
clrmsg
Apply the calibration to all sources, both amplitude and phase
task 'clcal'
getn 3
sources ' '
calsour '3c286','1148-001',' '
calcode ' '
opcode 'cali'
gainver 1
gainuse 2
refant 24
bparm 0
interpol '2pt'
timer 0
antenna 0
doblank 1
go
Check the calibration results
task 'snplt'
source ' '
inver 2
inext 'cl'
stokes ' '
optype 'phas'
opcode 'alsi'
xinc 1
nplots 9
antenna 0
timer 0
tvinit
dotv 1
go
optype 'amp'
go
Test Imaging
Amplitude Calibrator
Ok, let's start with a few test images. First, we will image the amplitude calibrator. Because of the funny epoch conversion stuff, it is not quite at the center where it is expected. This is not a problem.
task 'imagr'
getn 3
source '3c286',' '
uvrange 0
docalib 1
gainuse 2
stokes 'i'
cellsize 10,10
imsize 512,512
antenna 0
niter 10000
overlap 1
DO3DIMAG 1
rashift 1800.00,0
decshift -920.00,0
go
clrmsg
After you have cleaned it a bit, this is what it looks like.
And this is the point spread function of the actual observations (called the dirty beam). It looks like the amplitude calibrator image before you started cleaning. Why?
getn 5
tvinit
tvlod
tvfiddle
Phase Calibrator
Ok, clean up after ourselves
getn 5;zap
getn 6;zap
Now do the imaging and light cleaning
tget imagr
source '1148-001',' '
rashift 0
decshift 0
go
Note that in this image, there is a lot of large-scale junk. Why?
And here is the dirty beam. Notice how the dirty beam looks like the initial image of the phase calibrator before you began to clean it. Why?
getn 5
tvinit
tvlod
tvfiddle
Imaging the Sun
Ok, to do the best job, we need to separate the Sun data from the rest of the dataset. First, cleanup after the phase calibrator imaging.
getn 5;zap
getn 6;zap
SPLIT
task 'split'
getn 3
source 'sun',' '
timer 0
stokes ' '
aparm 0
go
IMAGR
Now do an initial imaging and cleaning step.
tget imagr
getn 4
source ' '
docalib 0
gainuse 1
go
Here are some of the stages of my cleaning.
Self-Calibration
Ok, let's do some self-calibration. This is just the same as “normal” calibration, except that you are saying to yourself that you are less confident that you know what the source is supposed to look like.
We run exactly the same calibration software, it exactly the same manner. Because the phase calibrator was resolved at short spacings, and because it is quite difficult for us to clean the extended emission, I limit the (u,v) coverage. Note that this also is only doing phase calibration, not amplitude calibration.
tget calib
getn 4
get2n 7
solint 30/60
solmode 'p!a'
docalib 0
uvrange 0.5,0
calsour ' '
inver 0
snver 0
go
clrmsg
Check the results
task 'snplt'
inext 'sn'
inver 1
stokes ' '
optype 'phas'
tvinit
go
Note some of the really large phase deviations! The phase calibration was not perfect.
Image again, using the new calibration
getn 5;zap
getn 6;zap
getn 7;zap
tget imagr
docalib 1
gainuse 1
go
This one is a bit better.
More Self-Calibration
But we can do more. Now let's do both amplitude and phase calibration. First, we do a phase-only self-calibration on short timescales, to get rid of the phase jitter.
Phase Self-Cal
tget calib
getn 4
get2n 7
solint 20/60
solmode 'p!a'
docalib 0
uvrange 0.5,0
calsour ' '
inver 0
snver 0
go
clrmsg
Check
task 'snplt'
inext 'sn'
inver 2
stokes ' '
optype 'phas'
tvinit
go
Amplitude Self-Cal
Doing both phase and amplitude calibration requires far more from the data S/N. It is best to have a longer time interval for amplitude calibration.
tget calib
getn 5
solint 20
solmode 'A&P'
cparm(2) 1
go
clrmsg
Check
task 'snplt'
inext 'sn'
inver 1
stokes ' '
optype 'phas'
tvinit
go
optype 'amp'
go
Cleanup
Clean up the files. But save the initial “CALIB” uv dataset! It is the one with the current amplitude calibration information.
getn 6;zap
getn 7;zap
getn 8;zap
Final Imaging
tget imagr
getn 5
docalib 1
gainuse 1
Discussion
What have you learned?
Does your image look like this image?
What is different?
Have a look at http://images.nrao.edu/8 and see what additional information was used to generate the NRAO web image. How would such additional information change your image?