[daip] POSSM output file frequency bug?

[Jim Ulvestad]

Leonia Kogan wrote:
> 
> Hi,
> 
> I can look in that if there is no objection.
> 
> Leonia

OK, I was wondering whether there really is a problem.  Each 
channel has the same reference frequency, plus a different velocity.
I would assume that the frequency of each channel is supposed
to be the reference frequency f_0 plus f_0 times v/c.  In that
case, it looks to me like what is being reported is correct.

jim

> ----- Begin Included Message -----
> 
> >From owner-daip at kochab.cv.nrao.edu Mon Jun 11 23:24 MDT 2001
> Date: Mon, 11 Jun 2001 23:23:55 -0600
> From: Bryan Butler <bbutler at aoc.nrao.edu>
> To: daip at planetas.aoc.nrao.edu
> Subject: [daip] POSSM output file frequency bug?
> Sender: owner-daip at kochab.cv.nrao.edu
> Precedence: bulk
> Content-Type: text
> Content-Length: 3193
> X-Lines: 67
> Status: RO
> 
> is there a bug in the frequencies printed to file with POSSM?
> 
> i have a file for which the header looks like:
> 
> AIPS 3: Image=TITAN     (UV)         Filename=TITAN       .LINALL.   1
> AIPS 3: Telescope=VLA                Receiver=VLA
> AIPS 3: Observer=AG579               User #= 1953
> AIPS 3: Observ. date=29-NOV-1999     Map date=11-JUN-2001
> AIPS 3: # visibilities   1210144     Sort order  TB
> AIPS 3: Rand axes: UU-L-SIN  VV-L-SIN  WW-L-SIN  BASELINE  TIME1
> AIPS 3: ----------------------------------------------------------------
> AIPS 3: Type    Pixels   Coord value     at Pixel     Coord incr   Rotat
> AIPS 3: COMPLEX      3   1.0000000E+00       1.00  1.0000000E+00    0.00
> AIPS 3: STOKES       2  -1.0000000E+00       1.00 -1.0000000E+00    0.00
> AIPS 3: FREQ        15   4.2127266E+10       1.00  1.5625000E+06    0.00
> AIPS 3: IF           1   1.0000000E+00       1.00  1.0000000E+00    0.00
> AIPS 3: RA           1    02 41 35.368       1.00       3600.000    0.00
> AIPS 3: DEC          1    12 57 51.670       1.00       3600.000    0.00
> AIPS 3: ----------------------------------------------------------------
> AIPS 3: Coordinate equinox   -1.00
> AIPS 3: Rest freq      0.000         Vel type: RADIO   wrt YOU
> AIPS 3: Alt ref. value  1.00000E+05  wrt pixel    8.00
> AIPS 3: Maximum version number of extension files of type AN is   3
> AIPS 3: Maximum version number of extension files of type HI is   1
> AIPS 3: Maximum version number of extension files of type FQ is   1
> AIPS 3: Maximum version number of extension files of type PL is   1
> 
> and i run a POSSM on it, printing to an output file, and the output
> file looks like:
> 
> Header information
> 
> Source: TITAN
> RA(1950):    2 41 35.37        DEC(1950):  12 57 51.67
> OBS. DATE: 19991129          Time of record:   0/  5 31 34.2
> No. channels:    13           First channel plotted   2
> Vel. of chn. 1 (Km/s):   177.7889    Vel. incr.   -11.1127
> Bw (kHz):   1562.500
> Antenna #  0     name: *
> Rest freq. (MHz) :       0.0000      Av. weight :       0.2321
> 
> DATA follow with format: (1X,I5,2X,I3,2X,F12.4,3(2X,G15.6))
> 
> Channel  IF     Frequency     Velocity         Real(Jy)         Imag(Jy)
>      2    1    42127.2664      166.676         0.753434E-02    -0.132752E-02
>      3    1    42127.2664      155.564         0.956062E-02    -0.149945E-02
>      4    1    42127.2664      144.451         0.907225E-02    -0.855536E-04
>      5    1    42127.2664      133.338         0.115656E-01     0.142601E-03
>      6    1    42127.2664      122.225         0.939328E-02    -0.455845E-03
>      7    1    42127.2664      111.113         0.109159E-01    -0.331914E-03
>      8    1    42127.2664     100.0000         0.951055E-02     0.135396E-02
>      9    1    42127.2664      88.8873         0.903549E-02    -0.215920E-02
>     10    1    42127.2664      77.7746         0.104383E-01     0.509417E-04
>     11    1    42127.2664      66.6619         0.105138E-01     0.266062E-03
>     12    1    42127.2664      55.5492         0.994118E-02    -0.858782E-03
>     13    1    42127.2664      44.4365         0.860946E-02     0.243838E-02
>     14    1    42127.2664      33.3238         0.126266E-01    -0.890167E-03
> 
> why are all the frequencies the same?
> 
>         -bryan
> 
> ----- End Included Message -----