[daip] SNSMO

[Lynn D. Matthews]

I am experiencing some behavior with SNSMO that I am trying to
understand. I am using boxcar smoothing, smotype 'VLBI'.

To illustrate my concern, I have put in my ftp area a TASAV file
containing a series of test SN tables, as well as plot extensions.
(cfa-ftp.cfa.harvard.edu, cd outgoing/lmatthew, get snsmo_tst.fits.) I'm
using the rates for this illustration, but similar behaviors occur in the
phases/delays.

The relevant extension files are:

SN 88: original SN table, output by FRING (see PL 8)

SN 100: rates smoothed by 0.3333h, dobtween 1 (see PL 1) ; results
look sensible; smoothing time exceeds scan time, so each scan now has a
single value with zero slope across it.

SN 200: SN88 rates smoothed by 6h, dobtween 1 ; now "mini-slopes" appear
in the rates across many scans, while the last scan for each antenna has
zero rate slope.  Why these behaviors? (see PL 3)

CL 200: illustrates the effect of these "mini-slopes" on the resulting CL
table. (see PL 4)

SN 300: rates smoothed by 24 hours, dobtween 1: results look sensible; all
rates now have same value (see PL 6)


Sample inputs:
======================================================================
AIPS 1: SNSMO     Task which smooths and filters Solution(SN) tables.
AIPS 1: Adverbs     Values                 Comments
AIPS 1: ----------------------------------------------------------------
AIPS 1: INNAME     'BG118D'                Input UV file name (name)
AIPS 1: INCLASS    'SUB SP'                Input UV file name (class)
AIPS 1: INSEQ         2                    Input UV file name (seq. #)
AIPS 1: INDISK        2                    Input UV file disk unit #
AIPS 1: SOURCES    '0528+134'              Source list ' '=>all.
AIPS 1:            '4C39.25'  *rest ' '
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   'BOX'                   Smoothing function
AIPS 1: BPARM         0           0        Smoothing parameters
AIPS 1:              24           0.3333      0.3333   *rest 0
AIPS 1: CUTOFF        0                    Cutoff for functional forms
AIPS 1: DOBLANK      -1                    Blanked value interpolation
AIPS 1: SMOTYPE    'VLBI'                  Data to smooth
AIPS 1: CPARM      *all 0                  Range of allowed delays and
AIPS 1:                                    rates.
AIPS 1: INVERS       88                    Input SN table; 0=>highest
AIPS 1: OUTVERS     300                    Output SN table; 0=>new
AIPS 1: REFANT        9                    Reference antenna 0=>pick.
AIPS 1: BADDISK    *all 0                  Disks to avoid for scratch


Lynn Matthews