AIPS HELP file for HAFIX in 31DEC24
As of Fri Apr 26 16:07:04 2024
HAFIX: Task to recompute u,v,w when time is hour angle.
INPUTS
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 0=VLA, 1=VLB, 2=GMRT,
3=other 1 for EVLA
2 => subarray number 0=>all
3-4=>array center bx, meters
5-6=>array center by, meters
7-8=>array center bz, meters
Time and frequency info.
11 => UT1-UTC (sec)
12 => IAT-UTC (sec). 0: use
accumulated leap seconds.
13 => time shift used for the
correction, in second
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
OPTYPE ' '=>UVW is recalculated
for IAT+UVFIXPRM(13)
'DELT'=>UVW_old+UVW(IAT+DT)
-UVW(IAT)
DT = UVFIXPRM(13)
FQCENTER >= 0 -> center frequency axis
HELP SECTION
HAFIX
Type: Task
Use: This task is a modification of UVFIX design to diagnose
a possible time shift problem at the original UV data.
The input UVdata are the output of the task TI2HA,
which converted original IAT time into hour angle.
This task reads a row of the input data, stores the original
U,V,W, converts the given hour angle back to IAT time,
recalculates U,V,W for this time and for the shifted time
and finally adds the difference of the two sets of U,V,W
to the original U,V,W.
The idea is to correct the error at U,V,W because a possible
error at time.
The user can calculate (under control of OPTYPE) only one
time shift UVW output. This optin is usefull to see by eyes
the effect of the time shift.
**************************************************************
* This task includes many options left from the UVFIX task *
* They can be used later on the user's need *
**************************************************************
This task does not support moving sources since TI2HA and HA2TI
do not support them.
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......THE ONLY PARAMETER USED NOW IS UVFIXPRM(13)!!!!!!.
1 => now normally ignored. 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 it!)
12 => IAT-UTC in seconds. Default = value in AN file. (Use it!)
Typically = year-1961 which is OK until mid-1982; after 1982 it
is off 1 (or more) second(s). Accurate values for both UT1-UTC
and IAT-UTC can be obtained from USNO Bulletin no. 7. If this
parameter is 0, HAFIX uses the value returned by the routine
LPSEC. LPSEC will have to be updated everytime a leap second is
added. The value as of July 1, 1993 was 28 seconds.
------------------------------------------------------------
13 => The time shift, in seconds
This is the only parameter used practically now.
------------------------------------------------------------
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.
OPTYPE...' ' => recalculate UVW for the IAT time recalculated from
the given hour angle and corrected
by UVFIXPRM(13)
'DELT' => correct the existing UVW by the difference of U,V,W
calculated for the two IAT times:
IAT1-is the recalculated IAT from the given hour angle
IAT2-is IAT1 + plus UVFIXPRM(13)
FQCENTER,...> 0 => Change frequency axis reference pixel to
Nchan / 2 + 1
else => do not change reference pixel
EXPLAIN SECTION