I'm reducing archival data, and a flux calibrator was unfortunately not taken at the beginning and the end of the observation. It was only taken at the beginning, and when I read the data in with FILLM, FILLM says that the antennas moved between my flux cal and my phase cal/data. FILLM then puts the flux cal in a different UV file from the data/phase cal.
I'm thinking the antennas couldn't have moved THAT much over 15 minutes (and all i want is a flux anyway), so I'd still like to use the flux cal (also there are no appropriate recent fluxes for the phase cal in any of the NRAO databases that Claudia suggested.) Is there a way to
a) apply a flux calibration solution from another uv file?
or
b) relax FILLM's requirements so that it will not be so sensitive to moving antennas and put everything in one file?
or
c) append a source to another UV file? I know uvglu appends in frequency, but i don't think it appends sources.
Thanks!
Saturday, March 7, 2009
More Missing Flux Cals
Thursday, March 5, 2009
WBR Step 7C: Apply Your Calibration
After you have calibrated your calibrators, you are going to want to apply this calibration to your source data-- the object you actually care about imaging.
First, you need to make a CL table that interpolates the amplitude/phase solutions found every ~30 minutes for the phase calibrator to your source data. You can use CLCAL or VLACLCAL to do this. Let's say your sources are "PHS_CAL' and 'COOL_GAL', and you have a lovely SN table for 'PHS_CAL' which you determined using the steps in Section 6. Then your inputs to CLCAL will look like this:
AIPS 1: CLCAL Task to manage SN and CL calibration tables
AIPS 1: Adverbs Values Comments
AIPS 1: ----------------------------------------------------------------
AIPS 1: INNAME 'NICE_DATA' Input UV file name (name)
AIPS 1: INCLASS 'L BAND' Input UV file name (class)
AIPS 1: INSEQ 2 Input UV file name (seq. #)
AIPS 1: INDISK 1 Input UV file disk unit #
AIPS 1: SOURCES 'PHS_CAL' Source list to calibrate
AIPS 1: 'COOL_GAL' *rest ' '
AIPS 1: SOUCODE ' ' Source "Cal codes"
AIPS 1: CALSOUR 'PHS_CAL' Cal sources for calibration
AIPS 1: *rest ' '
AIPS 1: QUAL -1 Source qualifier -1=>all
AIPS 1: CALCODE ' ' Calibrator code ' '=>all
AIPS 1: TIMERANG *all 0 Time range to calibrate
AIPS 1: SUBARRAY 0 Subarray, 0=>all,
AIPS 1: ANTENNAS *all 0 Antennas selected, 0=> all
AIPS 1: SELBAND -1 Bandwidth to select (kHz)
AIPS 1: SELFREQ -1 Frequency to select (MHz)
AIPS 1: FREQID -1 Freq. ID to select.
AIPS 1: OPCODE ' ' Operation 'MERG','CALI',
AIPS 1: 'CALP'; ' ' => 'CALI'
AIPS 1: INTERPOL '2PT' Interpolation function,
AIPS 1: choices are: '2PT','SIMP',
AIPS 1: 'AMBG','CUBE','SELF','POLY',
AIPS 1: 'SELN'; see HELP for details
AIPS 1: CUTOFF 0 Interpolation limit in
AIPS 1: time (min); 0=> no limit.
AIPS 1: SAMPTYPE ' ' Smoothing function
AIPS 1: BPARM *all 0 Smoothing parameters
AIPS 1: ICUT 0.1 Cutoff for functional forms
AIPS 1: DOBLANK 0 Blanked value interpolation
AIPS 1: DOBTWEEN 0 > 0 -> smooth all sources
AIPS 1: together; else separate them
AIPS 1: SMOTYPE ' ' Data to smooth
AIPS 1: SNVER 0 Input SN table, 0=>all.
AIPS 1: INVERS 0 Upper SN table vers in a
AIPS 1: range. 0=>SNVER
AIPS 1: GAINVER 1 Input Cal table 0=>high
AIPS 1: GAINUSE 2 Output CAL table 0=>high+1
AIPS 1: REFANT 8 Reference antenna 0=>pick.
AIPS 1: BADDISK *all 0 Disks to avoid for scratch
Now CL table #2 has all the info you need to calibrate your data!
Next, you want to apply this calibration and split your 'COOL_GAL' data off into a single source file. For this, use SPLIT.
AIPS 1: SPLIT Task to split multi-source uv data to single source
AIPS 1: Adverbs Values Comments
AIPS 1: ----------------------------------------------------------------
AIPS 1: also works on single files.
AIPS 1: INNAME 'NICE_DATA' Input UV file name (name)
AIPS 1: INCLASS 'L BAND' Input UV file name (class)
AIPS 1: INSEQ 2 Input UV file name (seq. #)
AIPS 1: INDISK 1 Input UV file disk unit #
AIPS 1: SOURCES 'COOL_GAL' Source list
AIPS 1: *rest ' '
AIPS 1: QUAL -1 Source qualifier -1=>all
AIPS 1: CALCODE ' ' Calibrator code ' '=>all
AIPS 1: TIMERANG *all 0 Time range to copy
AIPS 1: STOKES ' ' Stokes type to pass.
AIPS 1: SELBAND -1 Bandwidth to select (kHz)
AIPS 1: SELFREQ -1 Frequency to select (MHz)
AIPS 1: FREQID -1 Freq. ID to select.
AIPS 1: BIF 0 Lowest IF number 0=>all
AIPS 1: EIF 0 Highest IF number 0=>all
AIPS 1: BCHAN 0 Lowest channel number 0=>all
AIPS 1: ECHAN 0 Highest channel number
AIPS 1: SUBARRAY 0 Subarray, 0=>all
AIPS 1: DOCALIB 2 > 0 calibrate data & weights
AIPS 1: > 99 do NOT calibrate weights
AIPS 1: GAINUSE 2 CL (or SN) table to apply
AIPS 1: DOPOL -1 If >0 correct polarization.
AIPS 1: BLVER -1 BL table to apply.
AIPS 1: FLAGVER 0 Flag table version
AIPS 1: DOBAND -1 If >0 apply bandpass cal.
AIPS 1: Method used depends on value
AIPS 1: of DOBAND (see HELP file).
AIPS 1: BPVER 1 Bandpass table version
AIPS 1: SMOOTH *all 0 Smoothing function. See
AIPS 1: HELP SMOOTH for details.
AIPS 1: OUTCLASS 'SPLIT' Output UV file name (class)
AIPS 1: OUTSEQ 0 Output UV file name (seq. #)
AIPS 1: OUTDISK 0 Output UV file disk unit #.
AIPS 1: DOUVCOMP -1 1 (T) => compressed data
AIPS 1: APARM *all 0 Control information:
AIPS 1: 1 = 1 => avg. freq. in IF
AIPS 1: multi-channel out
AIPS 1: = 2 => avg. freq. in IF
AIPS 1: single channel out
AIPS 1: = 3 => avg IF's also
AIPS 1: 2 = Input avg. time (sec)
AIPS 1: 3 > 0 => Drop subarrays
AIPS 1: 4 > 0 => calibrate weights
AIPS 1: 5 = 0 pass only xc data
AIPS 1: = 1 pass xc and ac data
AIPS 1: = 2 pass only ac data
AIPS 1: 6 > 0 add full source name
AIPS 1: to header
AIPS 1: NCHAV 0 Number of chan. to average.
AIPS 1: (used if APARM(1) = 1)
AIPS 1: <= 0 -> ALL
AIPS 1: CHINC 0 Channel incr. between output
AIPS 1: channels (used if APARM(1)=1)
AIPS 1: ICHANSEL *all 0 Array of channel start, stop,
AIPS 1: and increment numbers and IF
AIPS 1: number to be used when
AIPS 1: averaging in frequency.
AIPS 1: (used if APARM(1) = 2, 3)
AIPS 1: BADDISK *all 0 Disks to avoid for scratch
The most important things to have set here are DOCAL = 2 and GAINUSE=2. If you have done other fancy things like a baseline-dependent calibration or a bandpass calibration, you can also apply those here.
SPLIT will make a file with just the calibrated data for your source of interest. You'll need to flag this single-source file, and then you'll be ready to image!
Imaging with AIPS
Reader Elena has a question:
Could some of you indicate me a tutorial for imaging with AIPS ?
I would need something with examples, and possibly considering both point-like and extended sources.
So far I found this :
http://www-astro.physics.ox.ac.uk/~hrk/AIPS_TUTORIAL/HRK_AIPS_1.html#24.
It's not focused on imaging, but there are some useful images as examples. Besides, it doesn't consider the case when one can not self-calibrate (e.g. looking for all Stokes parameters), that would be very interesting for me.
My response is below.
Elena, I would suggest that you read the AIPS COOKBOOK section on imaging and check out the synthesis imaging summer school book on imaging as well. I also encourage you to play around with IMAGR and see how changing the different parameters changes the image.
Read more!
Wednesday, March 4, 2009
Why is imaging quick sometimes and slloooow others?
I have 6 sources, each with 2-3 hours of continuum L-band data on them. For five of them, imaging and self-calibration are really quite quick, but one of the sources takes a factor of 5-6 longer to image/calibrate than the others! Its correlator setup is not different, it was taken only one day previous to the other sources, and it has a similar amount of time on source. Any ideas about why imagr seems to choke for this source? Thanks!
If you have a question about AIPS that CANNOT be answered by reading the