; MBDLY ;--------------------------------------------------------------- ;! Fits multiband delays from IF phases, updates SN table ;# Task Utility VLBI OOP Calibration ;----------------------------------------------------------------------- ;; Copyright (C) 1995, 1998 ;; Associated Universities, Inc. Washington DC, USA. ;; ;; This program is free software; you can redistribute it and/or ;; modify it under the terms of the GNU General Public License as ;; published by the Free Software Foundation; either version 2 of ;; the License, or (at your option) any later version. ;; ;; This program is distributed in the hope that it will be useful, ;; but WITHOUT ANY WARRANTY; without even the implied warranty of ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ;; GNU General Public License for more details. ;; ;; You should have received a copy of the GNU General Public ;; License along with this program; if not, write to the Free ;; Software Foundation, Inc., 675 Massachusetts Ave, Cambridge, ;; MA 02139, USA. ;; ;; Correspondence concerning AIPS should be addressed as follows: ;; Internet email: aipsmail@nrao.edu. ;; Postal address: AIPS Project Office ;; National Radio Astronomy Observatory ;; 520 Edgemont Road ;; Charlottesville, VA 22903-2475 USA ;----------------------------------------------------------------------- ;--------------------------------------------------------------- MBDLY LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC MBDLY: Fits multiband delays from IF phases in SN table USERID User number. INNAME Main input file (name). INCLASS Main input file (class). INSEQ 0.0 9999.0 Main input file (seq. #). 0 => high INDISK 0.0 9.0 Disk unit #. 0 => any INVERS Input SN file version no. OUTVERS Output SN file version. BIF 0.0 16.0 First IF to use. 0=>1 EIF 0.0 16.0 Last IF to use. 0=>last TIMERANG Time Range is consider. SUBARRAY Subarray (default=1) FREQID Freuency ID (default=1) PRTLEV 0.0 10.0 Print fit results >=1 fits, 2=IF resids. APARM Editing parameters (1) = min SNR; def=5 (2) = max rate rms (deg) def = 50d (3) = max MBD rms (deg) def = 20d (4) = min. no. IFs. 0->all (5) = MBD Search range. def = ambiguity. <0. Use zero. (6) = 0=Keep Residual phase in cal UV data 1=Zero Residual phase in cal UV data. ---------------------------------------------------------------- MBDLY Type: Task Use: MBDLY fits multiband delays from the IF phases in an SN table produced by FRING. The results are placed in another SN table. Adverbs: USERID......The user ID of the owner of the image. 0 => current user, 32000 => any user. INNAME......Main file name (name). Standard defaults. INCLASS.....Main file name (class). Standard defaults. INSEQ.......Main file name (seq. #). 0 => highest INDISK......Disk drive # of image. 0 => any INVERS......Input extension file version #. OUTVERS.....Output extension file version #. 0=>make new BIF.........First IF to use. 0=> 1. Use to determine MBDLY for dual frequency SN table EIF.........Last IF to use. 0=> last. Use to determine MBDLY for dual frequency SN table. TIMERANG....Time range to consider PRTLEV......<= 1.0 -> show multiband fits. >= 2.0 -> show phase residuals for each IF Use 1 for useful, but succinct information APARM.......Editing control parameters: (1) is the minimum average SNR (WEIGHT in the SN table). 0 => 5. 0.01 lets everything by. (2) is the maximum acceptable rate scatter among the IFs in units of degrees over the integration period. The default is 50 degrees. (3) is the maximum acceptable rms residual phase of the IF phase residual in degrees. The default is 20 deg. (4) is the minimum number of IF's for a valid solution. The default is all (EIF-BIF+1 or NUMIF) (5) is the search range (+/- value) for the MBD. Default is the natural range and is equal to the residual of the least-common stepping frequency. If <0, then assume MBDLY = 0. This is useful for just averaging the phases over the IF's. (6) If =0, keep residual phase in data. This will leave the observed phase in the data after removing the multiband slope. Use with CL2HF. If =1, Remove residual phase from data. This will zero the observed phase. The phase inserted in the SN table is the average observed phase. Use this option for further imaging. ---------------------------------------------------------------- PROGRAM: MBDLY DOCUMENTOR: Ed Fomalont 95.03.08 RELATED PROGRAMS: FRING, SNCOR, CL2HF, HF2SV, BLING, BLAPP PURPOSE FRING is used to determine the phase rate with time, the phase rate with frequency and the residual phase at some reference frequency for each IF over a short period of time. The results are placed in an SN table. The program MBDLY then reads this SN table (INVERS) to determine the best phase slope through the residual phases of the specified IF's. The results are put in a new SN table (OUTVERS). This delay over all of the IF's is called the Multi-band delay or the Group delay and it is often used in geodetic/astrometric experiments. The advantage is that the Group delay is not subject to lobe ambiguities associated with the phase. The peculiar phase constants for each IF must be determined and removed before MBDLY can calculate the phase slope. The peculiar phases can be obtained from special phase calibrations during the observations, or by a manual phase calibration. The easiest method to determine the manual phase calibration is to pick a short segment of data (less than a minute) for a strong source with a complete set of data. Run FRING on this segment to obtain the SBD, rate and phase. It is best to zero the rates from this solutions (and perhaps the SBD). Apply this solution to the entire data base using CLCAL. This will line-up the IF phases and define the multiband delay for the data segment equal to zero for all antennas. The Multiband delays can also obtained directly from FRING with APARM(5)=2.0. This is recommended for weak sources where the best signal to noise is required. For strong sources in astrometric experiments, it is best to use FRING with APARM(5)=0 and then MBDLY. Since the phases are sampled at a few discrete IF frequencies, the best slope is ambiguous by an amount (1000/DF) nsec, where DF is the basic IF frequency spacing (MHz). For example, if the IF spacings are 0, 80, 140, 400 MHz (above a reference value), then DF is 20 MHz. The ambiguity spacing of the MBDLY is then 50 nsec. For astrometric/geodetic experiments, the results in the SN table produced by MBDLY are interpolated into the CL table using CLCAL. Then, the task CL2HF calculates relevant astrometric quantities needed for the Calc/Solve software and places these results in an HF extension file. Finally the task HF2SV translates the HF data into something that can be read into Calc/Solve. See instructions associated with these two tasks. Parameters: BIF, EIF - The beginning and the ending IF to use for the solution. Experiments with simultaneous S/X bands are common. If the data base is not split into two separate frequency parts, then MBDLY must be run twice. As an example, consider the common case where IF's 1 to 4 contain SBAND data and IF's 5 to 8 contain XBAND data. FRING can be executed on the combined data base since each IF solution is independent. MBDLY must be run twice. First, with BIF=1; EIF=4 and then with BIF=5; EIF=8. The outputs must be put in different SN tables and CLCAL'ed separately. If APARM(4) = 0; then only solutions with all IF's will be accepted. TIMERANG - The time range of the input SN table to process. 0 means take everything. PRTLEV - Use 1 for most execution. This will list some information about the fits, including the rms phase residual. Use 2 to see the residual phase error for each IF. An offset in the phase calibration can be seen in this listing. Check the rms of the fits. They should be less than about 10 or 15 degrees for a good fit. APARM - Editting control parameters. Any SN table entry that exceeds one or more of the following criteria, will have a blanked multiband delay written in the output. APARM(1) - The default is an SNR of >5. This is reasonable. To include all data, let APARM(1) = 0.01 APARM(2) - This is the maximum phase scatter over the integration time which is caused by the scatter in the rate solutions for the IF's. The default is 50 degrees. This could be set to 10 degrees for good data. This option removes source solutions which have significantly different phase rates amongst the processed IF's. It is a good indication of bad data or a weak source. APARM(3) - The maximum phase scatter in the IF's after the removal of the best MBD. The default is 20 degrees. This could be set to 7 degrees for good data. APARM(4) - The minimum number of IF's. This is defaulted to them all considered in the solutions (EIF-BIF+1). If eight IF's are being used, then the default could be set to 6 or 7. The depends on the frequency sampling. APARM(5) - The MBD Search Range. The default is the natural ambituity range which is equal to the inverse of the 'unit' spacing in the frequency set. For example, if the four IF relative frequencies are 0, 70, 385, 490 MHz, then the unit frequency sampling is 35 MHz, or 28.6 nsec which is the default. For frequencies which are not commensurate, aparm(5) should be set to a reasonable range. If APARM(5)<0, then assume MBDLY is zero and just average phases in IF's. This is useful for getting the average phase over all of the IF's for a weak source. APARM(6) - If you want the residual phase to remain in the data, then set APARM(6)=0. This option is most useful if the fits will be analyzed in Calc/Solve, using CL2HF and HF2SV. If you want the residual phase to be zero, then set APARM(6)=1. This option is more useful if imaging and is equivalent to self-calibration.