public:meetings:glowbi2008:tutorial_monday

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

images.nrao.edu_images_sun_vr16c_lo.jpg

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

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.

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

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

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.

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

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

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

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

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

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

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

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

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

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''

inext 'sn'
inver 2
extdest
tget calib
go
clrmsg

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

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

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

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

task 'split'
getn 3
source 'sun',' '
timer 0
stokes ' '
aparm 0
go

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.

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

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.

getn 5;zap
getn 6;zap
getn 7;zap
tget imagr
docalib 1
gainuse 1
go

This one is a bit better.

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.

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

task 'snplt'
inext 'sn'
inver 2
stokes ' '
optype 'phas'
tvinit
go

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

task 'snplt'
inext 'sn'
inver 1
stokes ' '
optype 'phas'
tvinit
go
optype 'amp'
go

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

tget imagr
getn 5
docalib 1
gainuse 1

Discussion

What have you learned?

Does your image look like this image? images.nrao.edu_images_sun_vr16c_lo.jpg

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?

  • Last modified: 2017-03-08 15:27
  • by 127.0.0.1