[daip] [!8252]: AIPS - RLDLY: output SN-table phases not consistent with delays (DOIFS=1)
Michael Bietenholz
do-not-reply at nrao.edu
Tue Apr 5 08:59:42 EDT 2016
Michael Bietenholz updated #8252
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RLDLY: output SN-table phases not consistent with delays (DOIFS=1)
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Ticket ID: 8252
URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/8252
Full Name: Michael Bietenholz
Email: mbieten at yorku.ca
Creator: User
Department: AIPS Data Reduction
Staff (Owner): -- Unassigned --
Type: Issue
Status: Open
Priority: Default
SLA: NRAO E2E
Template Group: Default
Created: 05 April 2016 12:59 PM
Updated: 05 April 2016 12:59 PM
Due: 07 April 2016 12:59 PM (2d 0h 0m)
Resolution Due: 13 April 2016 12:59 PM (8d 0h 0m)
Is it me or RLDLY (31DEC16) that is confused? For DOIF=1, and the coordinate increment between channels *is* the same sign as that between IFs, I would have thought that the difference in SN-table delay between two IFs would be functionally related to the difference in SN-table phases. This doesn't seem to be the case.
I just ran RLDLY with DOIFS=1 (BIF=EIF=0) and got the output below, in particular the RL delay seems to be 4.2225 nsecs. I would have thought that the L phase difference between each pair of IFs should be just delta_freq * 4.2225 nsecs.
This almost true for IFs 1-4, which have 16.0 MHz between them (LISTR, OPTY='SCAN' output as well as IMHEAD output appended below), so one would expect 4.2225e-9*16e6*360degs = (-) 24.3 degs. The phase offsets in the RLDLY output (and in the SN table) are are close, but seem significantly off from this at -31.1 degs.
Then between IFs 4 and 5, which are 30.5 MHz apart, I would have expected a phase difference of -46.4 degs, but instead I find +120.6 degs. POSSM output concurs that RL visibility phases were better aligned between IFs *before* RLDLY.
RLDLY1 14:02:13 Determining solutions
RLDLY1 14:02:13 Time= 0/ 16 06 39 refant= 2
RLDLY1 14:02:13 QINIT: did a GET of 5120 Kwords, OFF 17573935572413
RLDLY1 14:02:13 Found 32 good solutions
RLDLY1 14:02:13 IF RL delay (ns) +- fe rms L phase (deg)
RLDLY1 14:02:13 1 4.2225 4.0385 0.0000 0.0
RLDLY1 14:02:13 2 4.2225 4.0385 0.0000 -31.1
RLDLY1 14:02:13 3 4.2225 4.0385 0.0000 -62.2
RLDLY1 14:02:13 4 4.2225 4.0385 0.0000 -93.3
RLDLY1 14:02:13 5 4.2225 4.0385 0.0000 27.3
RLDLY1 14:02:13 6 4.2225 4.0385 0.0000 -3.8
RLDLY1 14:02:13 7 4.2225 4.0385 0.0000 -34.9
RLDLY1 14:02:13 8 4.2225 4.0385 0.0000 -66.0
Frequency Table summary uses reference channel 17.00
FQID IF# Freq(GHz) BW(kHz) Ch.Sep(kHz) Sideband Bandcode
1 1 4.93275000 16000.0010 500.0000 1
2 4.94875000 16000.0010 500.0000 1
3 4.96475000 16000.0010 500.0000 1
4 4.98075000 16000.0010 500.0000 1
5 5.01125000 16000.0010 500.0000 1
6 5.02725000 16000.0010 500.0000 1
7 5.04325000 16000.0010 500.0000 1
8 5.05925000 16000.0010 500.0000 1
IMH output:
AIPS 1: Image=MULTI (UV) Filename=GB074-SCAN1 .UVCOP . 1
AIPS 1: Telescope=VLBA Receiver=VLBA
AIPS 1: Observer=GB074 User #= 1977
AIPS 1: Observ. date=22-OCT-2014 Map date=05-APR-2016
AIPS 1: # visibilities 3140 Sort order TB
AIPS 1: Rand axes: UU-L-SIN VV-L-SIN WW-L-SIN TIME1 SUBARRAY
AIPS 1: SOURCE FREQSEL INTTIM GATEID CORR-ID ANTENNA1
AIPS 1: ANTENNA2
AIPS 1: ----------------------------------------------------------------
AIPS 1: Type Pixels Coord value at Pixel Coord incr Rotat
AIPS 1: COMPLEX 3 1.0000000E+00 1.00 1.0000000E+00 0.00
AIPS 1: STOKES 4 -1.0000000E+00 1.00 -1.0000000E+00 0.00
AIPS 1: FREQ 32 4.9327500E+09 17.00 5.0000000E+05 0.00
AIPS 1: IF 8 1.0000000E+00 1.00 1.0000000E+00 0.00
AIPS 1: RA 1 00 00 00.000 1.00 3600.000 0.00
AIPS 1: DEC 1 00 00 00.000 1.00 3600.000 0.00
AIPS 1: ---------------------------------------------------------------
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