AIPS HELP file for UVFIXPRM in 31DEC22
As of Thu Jan 27 23:16:12 2022
Type: Adverb (Real(20))
Use: The task specific parameters for UVFIX. Specifies
geometry and time information.
Null value: Usually 0.
HAFIX....Recomputes u,v,w when time is hour angle (UVdata is output of
UVFIX....Recomputes u, v, and w with optional tangent point shift.
1 => array type, 0=VLA, 1=VLBI, 2=other.
2 => array number, 0 => loop over all.
3+4 => array BX, meters. (proper defaults for UVFIXPRM(1)=
5+6 => array BY, meters. 0 or 1)
7+8 => array BZ, meters.
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
desired. NOTE: EVLA uses the earth center (0,0,0).
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
file. EVLA times are not in error.
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.