AIPS NRAO AIPS HELP file for UVFIXPRM in 31DEC22



As of Thu Jan 27 23:16:12 2022



HELP SECTION

UVFIXPRM
Type: Adverb   (Real(20))
Use:  The task specific parameters for UVFIX.  Specifies
      geometry and time information.
Null value:  Usually 0.
Tasks:
  HAFIX....Recomputes u,v,w when time is hour angle (UVdata is output of
           TI2HA)
  UVFIX....Recomputes u, v, and w with optional tangent point shift.

Details:
     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.
      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.  NOTE: EVLA uses the earth center (0,0,0).
     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.  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
        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.

EXPLAIN SECTION


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