[daip] [!12908]: AIPS - Fring passing failed solutions as good

Thu Nov 1 23:08:39 EDT 2018

Jeffrey Hodgson updated #12908
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Fring passing failed solutions as good
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           Ticket ID: 12908
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/12908
                Name: Jeffrey Hodgson
       Email address: jhodgson at mpifr-bonn.mpg.de
             Creator: User
          Department: AIPS Data Reduction
       Staff (Owner): -- Unassigned --
                Type: Issue
              Status: Open
            Priority: Default
                 SLA: NRAO E2E
      Template group: Default
             Created: 02 November 2018 03:08 AM
             Updated: 02 November 2018 03:08 AM
           Reply due: 06 November 2018 03:08 AM (4d 0h 0m)
      Resolution due: 29 July 2021 12:00 AM (999d 20h 52m)

Hi,I am currently analysing some Korean VLBI Network datasets. There seems to be an issue in AIPS where Fring is finding good solutions even though they are below the SNR threshold. In this example, I am using 22 GHz data. I am using the following settings:
AIPS 2: FRING: Task to fringe fit dataAIPS 2: Adverbs Values CommentsAIPS 2: ----------------------------------------------------------------AIPS 2: Input uv data.AIPS 2: INNAME 'BOGAN2' UV file name (name)AIPS 2: INCLASS 'KVN1' UV file name (class)AIPS 2: INSEQ 1 UV file name (seq. #)AIPS 2: INDISK 1 UV file disk drive #AIPS 2: Data selection (multisource):AIPS 2: CALSOUR 'J1400+3149' Calibrator sourcesAIPS 2: 'J1400+3149' 'J1400+3149'AIPS 2: 'J1400+3149' 'J1400+3149'AIPS 2: 'J1400+3149' 'J1400+3149'AIPS 2: 'J1400+3149' 'J1400+3149'AIPS 2: 'J1400+3149' 'J1400+3149'AIPS 2: 'J1400+3149' 'J1400+3149'AIPS 2: 'J1400+3149' 'J1400+3149'AIPS 2: 'J1400+3149' 'J1400+3149'AIPS 2: 'J1400+3149' 'J1400+3149'AIPS 2: 'J1400+3149' 'J1400+3149'AIPS 2: 'J1400+3149' 'J1400+3149'AIPS 2: 'J1400+3149' 'J1400+3149'AIPS 2: 'J1400+3149' 'J1400+3149'AIPS 2: 'J1400+3149' 'J1400+3149'AIPS 2: 'J1400+3149'AIPS 2: QUAL -1 Calibrator qualifier -1=>allAIPS 2: CALCODE ' ' Calibrator code ' '=>allAIPS 2: SELBAND -1 Bandwidth to select (kHz)AIPS 2: SELFREQ -1 Frequency to select (MHz)AIPS 2: FREQID -1 Freq. ID to select.AIPS 2: TIMERANG *all 0 Time range to use.AIPS 2: BCHAN 1 Lowest channel number 0=>allAIPS 2: ECHAN 0 Highest channel numberAIPS 2: CHINC 1 Spectral channel incrementAIPS 2: (data are averaged)AIPS 2: ANTENNAS *all 0 Antennas to select. 0=allAIPS 2: DOFIT *all 0 Subset of ANTENNAS listAIPS 2: ** press RETURN for more, enter Q or next line to quit print **#AIPS 2: for which solns are desired.AIPS 2: SUBARRAY 0 Subarray, 0=>allAIPS 2: UVRANGE 0 0 Range of uv distance for fullAIPS 2: weightAIPS 2: WTUV 0 Weight outside UVRANGE 0=0.AIPS 2: WEIGHTIT 0 Modify data weights functionAIPS 2:AIPS 2: Cal. info for input:AIPS 2: DOCALIB 1 > 0 calibrate data & weightsAIPS 2: > 99 do NOT calibrate weightsAIPS 2: GAINUSE 1 CL table to apply.AIPS 2: DOPOL -1 If >0 correct polarization.AIPS 2: PDVER 0 PD table to apply (DOPOL>0)AIPS 2: BLVER -1 BL table to apply.AIPS 2: FLAGVER 0 Flag table versionAIPS 2: DOBAND -1 If >0 apply bandpass cal.AIPS 2: Method used depends on valueAIPS 2: of DOBAND (see HELP file).AIPS 2: BPVER -1 Bandpass table versionAIPS 2: SMOOTH *all 0 Smoothing function. SeeAIPS 2: HELP SMOOTH for details.AIPS 2:AIPS 2: CLEAN map (optional)AIPS 2: IN2NAME ' ' Cleaned map name (name)AIPS 2: IN2CLASS ' ' Cleaned map name (class)AIPS 2: IN2SEQ 0 Cleaned map name (seq. #)AIPS 2: IN2DISK 0 Cleaned map disk unit #AIPS 2: INVERS 0 CC file version #.AIPS 2: NCOMP *all 0 # comps to use for model.AIPS 2: 1 value per fieldAIPS 2: FLUX 0 Lowest CC component used.AIPS 2: NMAPS 0 No. Clean map filesAIPS 2: CMETHOD ' ' Modeling method:AIPS 2: 'DFT','GRID',' 'AIPS 2: CMODEL ' ' Model type: 'COMP','IMAG'AIPS 2: 'SUBI' (see HELP re images)AIPS 2: SMODEL *all 0 Source model, 1=flux,2=x,3=yAIPS 2: ** press RETURN for more, enter Q or next line to quit print **#AIPS 2: See HELP SMODEL for models.AIPS 2:AIPS 2: Output uv data file.AIPS 2: DOAPPLY 0 >= 0 write outputAIPS 2: OUTNAME ' ' UV file name (name)AIPS 2: OUTCLASS ' ' UV file name (class)AIPS 2: OUTSEQ 0 UV file name (seq. #)AIPS 2: OUTDISK 1 UV file disk drive #AIPS 2:AIPS 2: Solution control adverbs:AIPS 2: REFANT 1 Reference antennaAIPS 2: SEARCH *all 0 Prioritized reference antennaAIPS 2: list - supplements REFANTAIPS 2: - but only if APARM(9)>0AIPS 2: SOLINT 0.5 Solution interval (min)AIPS 2: 0 => 10 minAIPS 2: SOLSUB 0 Solution subintervalAIPS 2: SOLMIN 0 Min solution intervalAIPS 2:AIPS 2: APARM 3 0 General parametersAIPS 2: 0 0 1=min. no. antennasAIPS 2: 1 3 2 > 0 => data dividedAIPS 2: 10 *rest 0 3 > 0 => avg. RR,LLAIPS 2: 4 > 0 => avg. freq. in IFsAIPS 2: 5 = 1 => combine all IFsAIPS 2: = 2 => also MB delayAIPS 2: = 3 => combine IFs inAIPS 2: halvesAIPS 2: = 4 => combine IFs inAIPS 2: thirdsAIPS 2: = N => combines IFs inAIPS 2: N-1 piecesAIPS 2: SEE HELP WARNINGAIPS 2: 6=print level, 1=someAIPS 2: 7=SNR cutoff (0=>5)AIPS 2: 8=max. ant. # (no AN)AIPS 2: 9 > 0 => do exhaustiveAIPS 2: ** press RETURN for more, enter Q or next line to quit print **#AIPS 2: baseline searchAIPS 2: 10 > 0 -> fit dispersionAIPS 2: and IF group delay afterAIPS 2: fit of SB delaysAIPS 2: DPARM 0 300 Delay-rate parametersAIPS 2: 300 *rest 0 1=no. bl combo. (def=3)AIPS 2: 2=delay win (nsec), if  min. found in dataAIPS 2: 5 >0 => don't do ls. solnAIPS 2: 6 >0 => don't avg. in freqAIPS 2: 7 >0 => don't rereferenceAIPS 2: phaseAIPS 2: 8 > 0 => activate zero'ingAIPS 2: optionsAIPS 2: 9 > 0 => do not fit rateAIPS 2: SNVER 0 Output SN table, 0=>new tableAIPS 2: ANTWT *all 0 Ant. weights (0=>1.0)AIPS 2: BIF 0 First IF included whenAIPS 2: APARM(5) > 0AIPS 2: EIF 0 Last IF included whenAIPS 2: APARM(5) > 0AIPS 2: BADDISK *all 0 Disk no. not to use forAIPS 2: scratch files.>(Sorry for the awkward pasting).The problem is that in the AIPS output, no scans with SNR>10 are found, yet will report many good solutions:FRING2: Found 484 good solutionsFRING2: Failed on 968 solutionsFRING2: Adjusting solutions to a common reference antennaFRING2: Some solutions were not adjusted to the commonFRING2: reference antenna. This may be because one or moreFRING2: antennas were not used. Check your data beforeFRING2: proceeding.FRING2: Appears to have ended successfullyFRING2: localhos 31DEC16 TST: Cpu= 236.2 Real= 237 IO= 454And will pass the failed solutions through as good, leading (ultimtaely) to FITTP output files that are actually just noise. Do you have any idea how to solve this?Cheers!Jeff


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