; UVFIX ;--------------------------------------------------------------- ;! Recomputes u,v,w for a uv database ;# Task UV ;----------------------------------------------------------------------- ;; Copyright (C) 1995, 1997, 1999, 2003-2004, 2006-2010, 2013-2014 ;; 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 ;----------------------------------------------------------------------- UVFIX LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC UVFIX Task to recompute u,v,w terms for a uv database. INNAME Input UV file name (name) INCLASS Input UV file name (class) INSEQ 0.0 9999.0 Input UV file name (seq. #) INDISK 0.0 9.0 Input UV file disk unit # OUTNAME Output UV file name (name) OUTCLASS Output UV file name (class) OUTSEQ -1.0 9999.0 Output UV file name (seq. #) OUTDISK 0.0 9.0 Output UV file disk unit #. SHIFT Position shift(RA,Dec) asec. UVFIXPRM Array geometry 1 => array if needed 2 => subarray number 0=>all 3-4=>array bx, meters 5-6=>array by, meters 7-8=>array bz, meters Time and frequency info. 11 => UT1-UTC (sec) 12 => time-UTC (sec). 13 => clock error 14 => Freq (Hz) If .LE.0 use value in AN file 15 OB table number 0 => 1 16 Number of the orbiting antennas; 0=>there is no an orbiting antenna 17 Besselian epoch of data 18 differential aberration 0 => include 1 => not include 20 > 0 do not compute u,v,w INVERS -1.0 Version of CL or FO table to use for Doppler offsets: 0->1 FQCENTER >= 0 -> center frequency axis ---------------------------------------------------------------- UVFIX Type: Task Use: Computes values of u, v, w for one or more subarrays in a uv database and can shift the tangent point of single-source data. Correct phase shifting is done, so even large shifts are allowed. However, if the original u,v,w values require precession to J2000 or contain other significant "errors", then a more accurate shift will be obtained by running UVFIX twice, the first to correct the u,v,w's to the original (J2000) position and the second to shift the phases and u,v,w's to the new position. Any sort order will work, but time ordered data will probably run faster. NOTE: if the original sort order is neither 'TB' or 'BT' the output sort order is set to '**'. UVFIX may loop over subarrays if the same set of time and frequency correction values (UVFIXPRM) are applicable. If your data are multi-source data, UVFIX will run correctly, but no coordinate shifts are allowed. UVFIX includes differential abberation(Lorentz factor) now. Before April 98 this effect was calculated outside of AIPS. ************************************************************** * U, V, W are recalculated for J2000 in all cases. If * * the "epoch" of the data is neither 1950.0 nor 2000.0, * * then the coordinates are taken as apparent coordinates * * of date and precessed to J2000. If this is not correct * * do not use UVFIX. 1950.0 are converted from B1950 to * * J2000 meean coordinates. * ************************************************************** Orbiting antennas may be included. The GMRT uses a reversed phase convention which is supported as well. Beginning in Septemver 2009, UVFIX will take into account Doppler tracking of the observed frequencies. This only works if the Doppler offsets are recorded in either the CL table or an FO table. This correction will also be turned off if the data set contains more than one FQID or is not in TB order. 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. OUTNAME....Output UV file name (name). Standard defaults. OUTCLASS...Output UV file name (class). Standard defaults. OUTSEQ.....Output UV file name (seq. #). 0 => highest unique. OUTDISK....Disk drive # of output UV file.0 => highest w room. SHIFT......Desired position shift in the tangent point coordinates in arcseconds at the source. The new tangent point coordinates will be RA' = RA + SHIFT(1)/COS(DEC) and DEC' = DEC + SHIFT(2) where all coordinates are in arcseconds. NOTE: SHIFT(1) changed meaning to be like other shifts in AIPS 2003-02-20. UVFIXPRM......Specifies array geometry. 1 => array type, nomally ignored now. If the array center is to be changed, then one must set this parameter to 3. 2 => subarray number, 0 => loop over all. 3+4 => array BX, meters. (ONLY if UVFIXPRM(1)=3) Default is value in AN file 5+6 => array BY, meters. (ONLY if UVFIXPRM(1)=3) Default as BX. 7+8 => array BZ, meters. (ONLY if UVFIXPRM(1)=3) Default as BX. Here X is in the direction of the intersection of the meridian of the reference location (long=0 for earth centered) and the equator; Y is 90 deg. EAST along the equator from X; Z is in the direction of the N. pole. Note that: BX = UVFIXPRM(3) + UVFIXPRM(4), BY = UVFIXPRM(5) + UVFIXPRM(6), BZ = UVFIXPRM(7) + UVFIXPRM(8). The addition of two parameters allows the coordinates to be specified with more precision than a single adverb allows; on a 32-bit machines adverb values are only accurate to 7 significant digits. The array center is changed only if the two values are not zero - set set 10**-20 if 0 is desired. 11 => UT1-UTC in seconds. Default = value in AN file. (Use the default!) 12 => (uv data time)-UTC in seconds. Default = value in AN file under keyword DATUTC or, for the VLA (not EVLA), use the accumulated leap seconds.. (Use the default!) Accurate values for both UT1-UTC and IAT-UTC can be obtained from USNO Bulletin no. 7. A table of leap seconds is maintained in AIPS. 13 => Clock error. **** N.B. FILLM was corrected on 6 July 2007 in version 31DEC07 to write data times centered within the integration. Do not use this option for data loaded with that or later versions. **** For data loaded with earlier versions of FILLM, the time labels are in error by half of the MODCOMP online averaging time. Usually 5 seconds. (no default). The clock error is subtracted from times in the file. 14 => Frequency in Hz. If <= 0, the value in the AN, FQ, and SU files will be used. 15 OB table number; 0 => 1 16 The antenna number of the orbiting antenna; 0=>there is no an orbiting antenna; It is assumed that there is at most one orbiting antenna. Parameters #15 and #16 are not used for conventional (ground based) interferometry. Thus zeros are normally desirable. 17 Besselian epoch of data. When converting B1950 to J2000, the coordinates must first be converted to the observation date and then converted to J2000. 0 => 1979.3 which is okay for most VLA data. 18 0 => include differential aberration(Lorentz factor) 1 => not includes differential aberration(Lorentz factor) 20 > 0 => Do not recompute U, V, W. Users of the ATCA may want this option since the recomputation changes -NCP to -SIN projection for the U,V,W coordinates. Under all other circumstances, this option is not desirable. INVERS........Specifies the version of the CL or FO table to use to find the Dopler offsets. Normally, version 1 contains the Doppler offsets as written by the correlator, while later CL tables may be missing records or have other troubles. If you have computed Doppler offsets that have been added to the data (CVEL), then you should specify the highest CL table. 0 -> highest. FQCENTER,.....> 0 => Change frequency axis reference pixel to Nchan / 2 + 1 else => do not change reference pixel ----------------------------------------------------------------