; ATMCA ;--------------------------------------------------------------- ;! Determines delay/phase gradient from calibrator observations ;# Task Calibration ;---------------------------------------------------------------- ;; Copyright (C) 2004, 2008 ;; 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 ;----------------------------------------------------------------------- ATMCA LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC ATMCA Fits phase/delay slope to residual calibrator data INNAME Input UV file name (name) INCLASS Input UV file name (class) INSEQ 0.0 9999.0 Input UV file name (seq. #) INDISK Input UV file disk unit # SNVER Input SN table version 0 => last GAINVER Input CL table to copy 0=>high APARM control parameters: 1: Number of terms to fit 1=>Fit 1-D gradient 2=>Fit 2-D gradient 3=>Fit 2-D grad+offset 4=>like 3 + time slope 5=>Fit gradient along elevation 0 => 2 2: Create corrected CL table? 0 => not create 1 => create 3: Create residual SN table? 0 => not create 1 => create 4: Use the reference calibrator (first at the list) when APARM(1)= 2 0 => use 1 => do not use 5: Reference time (days) when the two-pi ambiguity is zero (OPTYPE='PHAS') 6: Intermediate and output SN tables: 0 => delete 1 => not delete SOURCES Sources to correct in the new CL table. ' '=>all CALSOUR List of the calibrators used to find the solution. The first source MUST be the primary reference source. STOKES Stokes type to process SELBAND Bandwidth to select (kHz) SELFREQ Frequency to select (MHz) FREQID Freq. ID to select, 0=>all BIF 0.0 100.0 Lowest IF number 0=>all EIF 0.0 100.0 Highest IF number 0=>all TIMERANG Time range to use. 0=>all ANTENNAS Antennas to select. 0=>all SUBARRAY 0.0 9999.0 Subarray; 0 => 1. SOLINT Solution time interval, in min. 0=> 30min OPTYPE What data to read from the SN table: 'PHAS' => phase delay 'MDEL' => multi band delay ' ' => 'PHAS' OUTTEXT Table of fitted slopes DOHIST >0 => put coefficients in history file. BADDISK 0.0 9999.0 Disks to avoid for scratch ---------------------------------------------------------------- ATMCA Task: This task determines the phase or delay slope from the residual data of nearby calibrators to the main reference source, and applies the appropriate correction to all sources. Adverbs: INNAME.....Input UV file name (name). Standard defaults. INCLASS....Input UV file name (class). Standard defaults. INSEQ......Input UV file name (seq. #). 0 => highest. INDISK.....Disk drive # of input UV file. 0 => any. SNVER......Input SN table with the residual MBDELAY or PHASE for the calibrators. 0 => highest. GAINVER....Input CL table version which is corrected if APARM(2)=1. 0 => highest input table. Output CL table is the next one after the highest APARM......control parameters (see explanation) 1: Number of terms to solve for correction. 1 => determine phase slope between main cal and secondary calibrator, and project this phase difference to the target. 2 => determine the 2-D phase slope using the main calibrator and at least two secondary calibrators, and apply to the target. 3 => also determine an offset phase. Need at least two secondary calibrators 4 => also determine a time rate of change. Need at least three secondary calibrators 5 => Fit gradient along elevation. 0 => 2 2: Create CL table? 0 => do not create 1 => create CL table with corrections 3: Create output SN table of result for sources in CALSOUR. 0 => do not create 1 => create. Results can be displayed by SNPLT for example 4: Use the reference calibrator (first at the CALSOUR list) when APARM(1)= 2 0 => use 1 => do not use 0 is recommended 5: Time (in days) when the phase for all sources and baselines has no two pi ambiguity. 6: When solving 2pi ambiguity, (OPTYPE = 'PHAS') the intermediate SN table with the solved phase is created. This table includes the solved phase (in degrees) at the column REAL, which can be plotted by SNPLT (OPTYPE='REAL'). The output SN table has the same format. These two tables should be deleted under control of APARM(6), because they can not be used at the following calibration due to strange REAL (degrees) and IMAG=0. You can leave them but then still delete them later (having examined) using verb EXTDEST. 0 => create 1 => not create SOURCES....List of the sources to apply the found correction at CL table. ' ' = all CALSOUR....List of the calibrators used to find the solution. The first source MUST be the main phase reference source or target if strong.. The output SN table include correction for the sources given at CALSOUR (not SOURCE) STOKES.....The desired Stokes type of the output data: 'R', 'L', ' '=> all available. SELBAN.....Bandwidth to select (kHz) SELFREQ....Frequency to select (MHz) FREQID.....Frequency ID to select. 0=>all BIF........First IF to process. 0=>all. EIF........Highest IF to process. 0=>all higher than BIF TIMERANG...Time range of the data to be used. In order: Start day, hour, min. sec, end day, hour, min. sec. Days relative to reference date. 0=>all ANTENNAS...A list of the antennas to be calibrated, plotted and corrected. If any number is negative then all antennas listed are ignored. All 0 => use all antennas. SUBARRAY...The subarray to calibrate. Does only one at a time. SOLINT.....Time interval in min to find a solution. This interval should must contain sufficient data to define a solution. 0=>30 min OPTYPE.....What data to read from the SN table: 'PHAS' => phase delay 'MDEL' => multi band delay ' ' => 'PHAS' OUTTEXT....Table of fitted delays and slopes for each solution intervals and antennas The values correspond to the desired corrections. DOHIST.....if DOHIST > 0, the gain coefficients are written into the history file. BADDISK....A list of disks on which scratch files are not to be placed. This will not affect the output file. ---------------------------------------------------------------- ATMCA: Task determines delay/phase gradients from calibrator observations, and applies the appropriate correction to the target sources. Documenters: L.R. Kogan, E.B. Fomalont Related Programs: DELZN, CLCAL, ELINT, SNPLT PURPOSE Please read AIPSMEMO111 for detailed instructions of the use of ATMCA. tp://ftp.aoc.nrao.edu/pub/software/aips/TEXT/PUBL/AIPSMEM111.PS Most phase referencing observations nod between a reference calibrator (0) and a target source (T). Errors in the correlator model (egs. troposphere and ionospheric refraction, antenna locations) introduce systematic phase differences between the 0 and T direction over each telescope, often with a time-scale of many minutes to hours of time. These errors decrease the dynamic range and astrometric accuracy of VLBI observations. To a first approximation, this phase difference can be described as a linear slope of anomalous delay over each of the telescopes within a region of about five to ten degrees near 0 and T. With observations of additional calibrator(s), the effect of this phase gradient can be decreased. PARAMETERS FOR ATMCA INNAME, INCLASS, INSEQ, INDISK: The input data set SNVER: The SN table which contains the antenna-based phases for of the sources to be analyzed by ATMCA. Source position offsets must have been removed. GAINVER: The CL table with the calibrations used to generate the SNVER table. A new CL table will be generated with the improved solution. ------------------------------------------------------------------- APARM(1) MAIN CONTROL OF ATMCA (see AIPSMEMO111) APARM(1)=1: Linear interpolation of phase of two calibrators to apply to target. The calibrators must be within 45 deg of colinear. APARM(1)=2: Determine phase slope and orientation. Three calibrators in a reasonable two-dimensional distribution must be used. APARM(1)=3: Phase/delay gradient and offset: Needs at least four calibrators APARM(1)=4: The same as APARM(1)=3 but a gradient in time is added to the list of found parameters. Needs at least five calibrators. APARM(1)=5: Assumes phase gradient is in the elevation direction. Can be used with two calibrators or one calibrator and a strong target. ------------------------------------------------------------------------ APARM(2): Create new CL table. A new CL table containing the additional phase terms for all designated sources in SOURCE, will be produced if APARM(2) = 1. APARM(3): Create a new SN table which contains the residuals for sources in CALSOUR after the correction is applied. This SN table is used to view the fitting result using SNPLT. It is not meant to be applied to a CL table using CLCAL. SOURCES: List of sources to correct. Often ' ' is the correct choice. It should include all of the calibrators and targets. CALSOUR: The first source MUST be the main reference source or the target if it is used as the main reference source. Other calibrator sources are then added. It is dangerous to use ' '. SOLINT: The time interval for obtaining a solution. The minimum time must contain sufficient phase measurements to obtain a solution. In order to decrease the effects of short-term atmospheric phase fluctuations, or phase noise of relatively weak calibrators, longer SOLINT can be considered. OUTTEXT: The output file for the solutions.