AIPS tut 1 The approach to dip

AIPS tut 1 • The approach: to dip into and out of AIPS several times, each time doing something more complicated. 1. Starting AIPS and exiting. 2. Loading a FITS image and displaying it. 3. Calibration of a continuum observation (an observation of a gravitationally lensed quasar by the MERLIN array in the UK) via a runfile. 4. Some CLEANing. • See chapter 3 of the AIPS Cookbook: – • ftp: //ftp. aoc. nrao. edu/pub/software/aips/TEXT/PUBL /COOK 3. PS. gz There are links to both the cookbook and the AIPS home page off my web site. NASSP Masters 5003 F - Computational Astronomy - 2009

• AIPS tut 1 Before you start AIPS, there a few things you will need to do. 1. Decide where you want to keep your FITS files. Maybe make a special directory for them. 2. Do export MYAREA=. 3. Decide where to keep ‘runfiles’ (AIPS scripts). 4. Do export RUNFIL=. 5. Obtain a user ID from the AIPS administrator (me). You will be given a decimal integer and an extended hexadecimal (ehex) version of this integer. NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 – Change the names of your runfiles so they end in. . Eg if your user ID number is 10, the ehex version of this is 00 A. Hence you should rename a runfile MERLIN. XXX to MERLIN. 00 A. • You are now ready to start aips. In the following steps I’ll show what you should type in greenish, leftish boxes, and what you see in response in pinkish, rightish boxes. A ® character means the ‘enter’ key. Any text between <> means that what you type there depends on circumstances. NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 • At your normal Unix command line, type aips notv® • You will see something like: You have a choice of 5 printers. These are: No. [ type ] Description ------------------------------1. [ PS] n 2. [ PS] Spare 3. [ PS] Main 4. [ PS] n 5. [ PS] n ------------------------------START_AIPS: Enter your choice, or the word QUIT [default is 3]: NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 • Just choose the default (ie hit enter). ® START_AIPS: Your initial AIPS printer is the Main START_AIPS: - system name , AIPS type PS START_AIPS: User data area assignments: (Using global default file for DADEVS. PL) Disk 1 (1) is /home/aips/AIPS/DATA/LOCALHOST_1 Tape assignments: Tape 1 is REMOTE Tape 2 is REMOTE START_AIPS: Starting TPMON daemons on LOCALHOST asynchronously. . . Starting up 31 DEC 09 AIPS with normal priority Begin the one true AIPS number 1 (release of 31 DEC 09) at priority = 0 AIPS 1: You are NOT assigned a TV device or server AIPS 1: You are NOT assigned a graphics device or server AIPS 1: Enter user ID number ? NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 ® AIPS AIPS AIPS > 1: 1: 1: 31 DEC 09 AIPS: Copyright (C) 1995 -2009 Associated Universities, Inc. AIPS comes with ABSOLUTELY NO WARRANTY; for details, type HELP GNUGPL This is free software, and you are welcome to redistribute it under certain conditions; type EXPLAIN GNUGPL for details. Previous session command-line history recovered. TAB-key completions enabled, type HELP READLINE for details. Recovered POPS environment from last exit • At this point you have landed on the planet of AIPS. You are within the AIPS private file system. AIPS runs a shell called POPS which is similar in many ways to Unix. Before we do anything interesting, let’s get back to Unix, just to prove that it’s possible to enter AIPS and live to tell the tale. NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 kleenex® AIPS 1: Begin check for any 'standard' scratch files AIPS 1: Scratch files -- destroyed: 0 still active: 0 AIPS 1: User 2: 4 messages, oldest written 22 -APR-2009 19: 02: 40 AIPS 1: Deleted 0 messages AIPS 1: Saved POPS environment in area named 'LASTEXIT' ► ► AIPS 1: Session command-line history saved. AIPS 1: localhos 31 DEC 09 TST: Cpu= 0. 0 Real= 9 IO= 2 $ • You are back in Unix. • Now we are going to import an image file into AIPS and display it. • AIPS grudgingly concedes that it has to communicate with files in the real world. So it will read and write FITS files (although it writes bad FITS which other programs can’t read). NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 • There are two principal file types in AIPS – lists of visibilities, and images. AIPS denotes these by the letter codes UV and MA respectively. • Before going further, download the file M 82_DIRTY. FITS from my website and put it into your previously selected AIPS data directory. This is a FITS file, an image, which is the product of previous AIPS manipulations. • Now do aips® NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 • You will get the same printer prompt as before; just choose the default again. • You’ll be prompted for your user ID same as before, but before you can type it in, AIPS will start up 3 more windows, and print a lot more text at the prompt. – The 3 extra windows are a Tek server, a Message server and a ‘TV’. • Just click back to focus on your original window, and enter your user ID then ®. Don’t worry that the ? prompt has got buried in extra output. • AIPS will give the same messages as before, ending with its POPS > prompt. NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 • Now we’re going to run a task. – AIPS talks about tasks but also things which it calls verbs. The difference is minor: • A task usually takes a while to run. Thus it is run in a ‘forked’ process, in the background, with output to the message server. You can type another command at the prompt in the mean time. • A verb is a quick-running task. There is no fork for these, you have to wait until the verb is finished before entering further commands. • The task we’re going to run is called FITLD. It is one of several AIPS tasks for importing FITS data (typical AIPS overkill). NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 • FITLD also has a lot of parameters to cover all kinds of special cases. Most of these can be left at default values. • (One source of confusion in AIPS is that parameters which have the same name in 2 or more different tasks remember their values from task to task. – The AIPS people claim this is a feature but I think it is a trap for the unwary. ) • AIPS is case insensitive (except for Unix file names). • You can use unambiguous shortening of parameter names. Eg indi instead of indisk. NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 • So, at the AIPS prompt, type task ‘fitld’ inp® • The inp requests a list of the FITLD parameters. There are pages of them. See next slide for the first page! – Note that the exact number of lines on the page depends on the size of your terminal window. It may be more or less than I have shown here. NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 AIPS AIPS AIPS AIPS AIPS AIPS AIPS # 1: 1: 1: 1: 1: 1: 1: FITLD: Task to store an image or UV data from a FITS tape Adverbs Values Comments --------------------------------INTAPE 1 Input tape drive # (0 => 1) NFILES 0 # of files to advance on tape DATAIN *all ' ' Disk file name OUTNAME ' ' File name (name) OUTCLASS ' ' File name (class) OUTSEQ 0 File name (seq. #) 0 => highest unique number => matching (on VLBA) -1 => FITS tape value OUTDISK 1 Disk drive # (0 => any) OPTYPE ' ' Type of data to load, ' ' => all types 'UV' => UV data 'IM' => images NCOUNT 0 Number of files to load. DOTABLE 1 True (1. 0) means load tables for images. DOUVCOMP 1 >0 => compressed data (FITS) DOCONCAT -1 >0 -> if VLBA or uv table, append data to existing files, or if no appropriate files exist create a new file and append all data to that ** press RETURN for more, enter Q or next line to quit print ** NASSP Masters 5003 F - Computational Astronomy - 2009

• • AIPS tut 1 Don’t worry that it talks about tapes – FITLD can read either from a disk or a tape – and is pretty clever about working out which it has to deal with. Try continued carriage returns until you run out of pages and get back to the > prompt. Now press the up-arrow key. You’ll get the inp back (same as Unix). Now press carriage return to list the params all over again. But test the early exit capability with q® NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 • To get FITLD to load the file you want, you only have to set 3 of the parameters. Do datain ‘MYAREA: M 82_DIRTY. FITS’ outname ‘M 82’ outclass ‘IIM 001’® • Note that AIPS reads the value of your MYAREA envar. It’s possible to type in the full Unix pathname but this parameter only accepts a string of maximum length 48 characters – ie really short. • If you have a file name with some lower case characters, leave off the final ‘ otherwise AIPS will convert whatever you type to upper case. • Do a final inp to check all params are set properly. NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 • Now do go® • In the MSGserver window (NOT the main window!) you should see: MSGserver: Starting AIPS task logging, Inet domain hostna> task #: Message --------------------localh> FITLD 1: Task FITLD (release of 31 DEC 09) begins localh> FITLD 1: Create FITLD. TEMP. 1 (MA) on disk 1 cno 1 localh> FITLD 1: RENAM M 82. IIM 001. 1 (MA) ON DISK 1 CNO 1 localh> FITLD 1: Image=M 82 (MA) Filename=M 82. IIM 001. 1 localh> FITLD 1: Telescope=MERLIN 2 Receiver= localh> FITLD 1: Observer= User #= 3 localh> FITLD 1: Observ. date=31 -MAY-2007 Map date=25 -SEP-2008 localh> FITLD 1: Minimum=-2. 68784468 E-03 Maximum= 1. 42841954 E-02 JY/BEAM localh> FITLD 1: --------------------------------localh> FITLD 1: Type Pixels Coord value at Pixel Coord incr Rotat localh> FITLD 1: RA---SIN 512 09 55 50. 704 256. 00 -0. 015000 0. 00 localh> FITLD 1: DEC--SIN 512 69 40 43. 591 257. 00 0. 015000 0. 00 localh> FITLD 1: FREQ 1 4. 5460000 E+09 1. 00 1. 4500000 E+07 0. 00 NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 localh> localh> localh> FITLD 1: FITLD 1: FITLD 1: FREQ 1 4. 5460000 E+09 1. 00 1. 4500000 E+07 0. 00 STOKES 1 1. 0000000 E+00 0. 00 --------------------------------Coordinate equinox 2000. 00 Map type=DIRTY Number of iterations= 0 Conv size= 0. 05000 X 0. 05000 Position angle= 0. 00 Rest freq 0. 000 Vel type: OPTICAL wrt YOU Alt ref. value 0. 00000 E+00 wrt pixel 1. 00 Maximum version number of extension files of type HI is 1 Appears to have ended successfully localhos 31 DEC 09 TST: Cpu= 0. 1 Real= 0 IO= 1 • Now do mcat® • This lists the image files you have in AIPS 1: Catalog on disk 1 AIPS 1: Cat Usid Mapname AIPS 1: 1 3 M 82 > Class Seq Pt Last access Stat. IIM 001. 1 MA 22 -APR-2009 19: 23: 59 NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 • Explanation of the various fields: – Cat: each file that AIPS stores has a unique catalog integer. As we’ll see in a minute, this can be a convenient way to grab a particular file. – Usid: should be your user ID integer. You can only see those files corresponding to that ID. – Mapname: should be what you supplied to the outname parameter of FITLD. – Class: should be what you supplied to the outclass parameter of FITLD. Note that all class names are 6 characters between two dots. NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 – Seq: each file with a given combination of name and class has a unique sequence integer. Note that AIPS policy is never to throw anything away. If you modify a file, you usually won’t overwrite the old file: it will just store it with an incremented sequence number. – Pt: either MA for image or UV for visibilities. – Last access: obvious. – Stat: if a task is busy in the background reading from or writing to a file, this ‘busy’ state will be indicated by the status. • Note that ucat will list UV files and pcat will list everything. NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 • AIPS lets you look at the ‘header’ (in a pseudofitsy kind of sense): imhead® AIPS AIPS AIPS AIPS AIPS > 1: 1: 1: 1: 1: Image=M 82 (MA) Filename=M 82. IIM 001. 1 Telescope=MERLIN 2 Receiver= Observer= User #= 3 Observ. date=31 -MAY-2007 Map date=25 -SEP-2008 Minimum=-2. 68784468 E-03 Maximum= 1. 42841954 E-02 JY/BEAM --------------------------------Type Pixels Coord value at Pixel Coord incr Rotat RA---SIN 512 09 55 50. 704 256. 00 -0. 015000 0. 00 DEC--SIN 512 69 40 43. 591 257. 00 0. 015000 0. 00 FREQ 1 4. 5460000 E+09 1. 00 1. 4500000 E+07 0. 00 STOKES 1 1. 0000000 E+00 0. 00 --------------------------------Coordinate equinox 2000. 00 Map type=DIRTY Number of iterations= 0 Conv size= 0. 05000 X 0. 05000 Position angle= 0. 00 Rest freq 0. 000 Vel type: OPTICAL wrt YOU Alt ref. value 0. 00000 E+00 wrt pixel 1. 00 Maximum version number of extension files of type HI is 1 Keyword = 'PARANGLE' value = 5. 211561 E+01 Keyword = 'ZENANGLE' value = 4. 789422 E+01 NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 • Now the fun begins. Do getn 1 tvall® • Note: getn 1 grabs the file with cat no 1. AIPS 1: 1: Hit Hit button A B C D to to enhance B/W or color alternately increment zoom & set zoom center decrement zoom & set zoom center exit • Note that you don’t get the AIPS > cursor back. The TV is in control now. NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 • The TV window should light up and display what is in the image. • You should see what looks like a single point source centred in a fairly cruddy field. Comments: – The field is cruddy because it is a dirty image. – The point source is actually a supernova remnant which may have gone off as recently as 1980. Observations spaced a few years apart show it expanding rapidly. • You’ll also note that the cursor becomes a purple cross when it crosses the TV. NASSP Masters 5003 F - Computational Astronomy - 2009

AIPS tut 1 • Click in the TV window to capture focus on it. Then press keyboard key b a couple of times. The display should zoom in. • Now click with left mouse button somewhere in the image: the image should recentre to where you clicked. • Press key a then drag the mouse over the image. You should be able to change the contrast and brightness. • Pressing a again gives you a false-colour map, with the same mouse drag capability. • There's lots more you can do with the TV. See the Cookbook chapter 6. 4. But for now we'll get out of the TV and then AIPS. Press the d key to get out of ‘TV mode'. This should get you back your AIPS > cursor. Then kleenex out to unix. – All the windows disappear eventually although it can take a few seconds. NASSP Masters 5003 F - Computational Astronomy - 2009