AIPS HELP file for UVFIX in 31DEC21
As of Fri Dec 4 3:22:30 2020
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
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
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.
UVFIX will support moving sources if there is a PO table.
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.
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
11 => UT1-UTC in seconds. Default = value in AN file. (Use the
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
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
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