[daip] [!5764]: aips - SNSMO with mode "VLMB" sometimes breaks the relationship between phase(per IF) and delay

[Michael Bietenholz]

Michael Bietenholz updated #5764
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SNSMO with mode "VLMB" sometimes breaks the relationship between phase(per IF) and delay
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           Ticket ID: 5764
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/5764
           Full Name: Michael Bietenholz
               Email: mbieten at yorku.ca
             Creator: User
          Department: AIPS Data Processing
       Staff (Owner): -- Unassigned --
                Type: Issue
              Status: Open
            Priority: Default
                 SLA: NRAO E2E
      Template Group: Default
             Created: 11 November 2014 03:35 PM
             Updated: 11 November 2014 03:35 PM
                 Due: 14 November 2014 03:35 PM (3d 0h 0m)
      Resolution Due: 20 November 2014 03:35 PM (9d 0h 0m)



If an SN table was made with FRING,DPARM(5)=1, then there should be a functional relationship between  the phase-difference  between the different IFs and the (multi-band) delay:  dphase =  360degs * (delay * dfreq)

In the attached TASAV, SN7 was made by FRING (31DEC13), and the relationship above seems to hold. However, after running it through SNSMO I get the following - just looking at the first point. In this case, IF1 and IF2 are 8.000 MHz apart.

SN13
22:02:30: IF1 phase = 114.0degs, IF2 phase = 86.8 degs => this corresponds to delay=-9444 picosecs
However, the SN table entry for the delay is                                                              -31230 picosecs

The attached PNG screenshot shows SNPLT OPCO='PHAS'; OPTY='IFDF': BIF 1; EIF 2 with SN7  (before SNSMO) in yellow and  SN13 (after SNSMO) in green.   You can see that after SNSMO,  the IF1-IF2 phase difference goes haywire before 1/08h, which of course causes the IF to IF coherence to fall apart.

This happens in both 31DEC13 and 31DEC14 versions of SNSMO

======= Here's the complete inputs to SNSMO

AIPS 1: SNSMO     Task which smooths and filters solution (SN) tables
AIPS 1: Adverbs     Values                 Comments
AIPS 1: ----------------------------------------------------------------
AIPS 1: INNAME     'MEKU'                  Input UV file name (name)
AIPS 1: INCLASS    'UVCOP'                 Input UV file name (class)
AIPS 1: INSEQ         1                    Input UV file name (seq. #)
AIPS 1: INDISK        1                    Input UV file disk unit #
AIPS 1: SOURCES    *all ' '                Source list ' '=>all.
AIPS 1: DOBTWEEN      1                    > 0 -> smooth all sources
AIPS 1:                                    together; else separate them
AIPS 1: SELBAND      -1                    Bandwidth to select (kHz)
AIPS 1: SELFREQ      -1                    Frequency to select (MHz)
AIPS 1: FREQID       -1                    Freq. ID to select, 0=>all
AIPS 1: BIF           0                    Lowest IF number 0=>all
AIPS 1: EIF           0                    Highest IF number 0=>all
AIPS 1: TIMERANG   *all 0                  Time range to use.
AIPS 1: ANTENNAS   *all 0                  Antennas to correct.
AIPS 1: SUBARRAY      0                    Subarray; 0 => all.
AIPS 1: SAMPTYPE   'GAUS'                  Smoothing function
AIPS 1: BPARM         6           6        Smoothing parameters
AIPS 1:               6           6           6           2
AIPS 1:               2           2           2           2
AIPS 1: CUTOFF        0                    Cutoff for functional forms
AIPS 1: DOBLANK       0                    Blanked value interpolation
AIPS 1: SMOTYPE    'VLMB'                  Data to smooth
AIPS 1: CPARM      *all 0                  Range of allowed delays and
AIPS 1:                                    rates.
AIPS 1: NPIECE        0                    Number IF groups used in
AIPS 1:                                    FRING (re APARM(5))
AIPS 1: NORMALIZ      0                    > 0 => apply a global
AIPS 1:                                    normalization - see HELP
AIPS 1: INVERS        7                    Input SN table; 0=>highest
AIPS 1: OUTVERS       0                    Output SN table; 0=>new
AIPS 1: REFANT        6                    Reference antenna 0=>pick.
AIPS 1: BADDISK    *all 0                  Disks to avoid for scratch

============  here's the messages SNSMO produced

******  11-NOV-2014  ******
SNSMO1 16:09:51 Task SNSMO  (release of 31DEC14) begins
SNSMO1 16:09:51 Copied SN file from vol/cno/vers  1   16   7 to  1   16  13
SNSMO1 16:09:51 SNREF: re-referencing   0.00% of table entries to antenna   6
SNSMO1 16:09:51 SNSMTH: Smoothing SN table
SNSMO1 16:09:51 Appears to have ended successfully
SNSMO1 16:09:51 dailyali 31DEC14 TST: Cpu=      0.0  Real=      0  IO=        14
AIPS 1: User 2177:  2482 messages, oldest written 




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