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operations:documentation:fivept_output

Fivept Output: What does it mean?

The main routine in a pointing run is fivept which makes point-by-point cross scans on a source to determine offsets. It's usually called during a pointing run in the aquire procedure but can also be called manually. The syntax for fivept is as follows (taken from the documentation at /usr2/fs/help/fivept.___:

fivept=axis,rep,pts,stp,intp,dev,wait

and acquire calls fivept with the following options:

fivept=azel,-2,9,.4,9,1u,120

where:

  • axis: The axis system for the scan (hadec, azel, xyns or xyew). For the 12m antennas it's azel
  • rep: Number of repetitions: -10 to -1 and 1 to 10 allowed. Default is -2. Negative repetition counts are described in the fivpt manual. The absolute value implies a maximum repetitions count, but once the scans are well centered on both axes, additional repetitions will be skipped.
  • pts: Number of points on each axis, if even, it is increased by 1. pts must be between -31 to -3 or 3 to 31, inclusive. Default is 7. Negative point counts cause the system temperature measurement to be skipped. The absolute value is used as the number of points.
  • stp: Step size for distance between points, in multiples of a beamwidth. Default is 0.5.
  • intp: Integration period, 1 to 32 seconds.
  • dev: Mnemonic for the device to be used as the detector.
  • wait: Seconds to wait for onsource for each point, 1-1200 seconds allowed, default 120.

fivept first attempts a scan in latitude (Elevation) and will show data for each of the sampled points (9 in the default case). At the end, a Gaussian with an underlying line is fit to the data. Typical output looks like this:

                                 N  Time    Offset     Amp    Err
2013.043.22:30:54.52#fivpt#lat   1  81050.  -0.3650    0.611  0.074 
2013.043.22:31:08.52#fivpt#lat   2  81064.  -0.2800    0.508  0.033 
2013.043.22:31:22.54#fivpt#lat   3  81078.  -0.1950    0.844  0.098 
2013.043.22:31:36.51#fivpt#lat   4  81092.  -0.1099    1.119  0.054 
2013.043.22:31:50.53#fivpt#lat   5  81106.  -0.0249    1.345  0.113 
2013.043.22:32:04.54#fivpt#lat   6  81120.   0.0601    0.679  0.093 
2013.043.22:32:18.54#fivpt#lat   7  81134.   0.1451    0.178  0.092 
2013.043.22:32:32.50#fivpt#lat   8  81148.   0.2301    0.014  0.054 
2013.043.22:32:46.50#fivpt#lat   9  81162.   0.3151   -0.151  0.048 

Where:

  • N is the point number
  • Time is the time tag (in seconds)
  • Offset is the pointing offset from nominal (in deg)
  • Amp is the amplitude of the measurmenent
  • Err is an estimate of the error in the measured amplitude
                                    Offset   Width   Amp     C       M        E_code
2013.043.22:32:46.50#fivpt#latfit  -0.04835  0.2266  1.0818  0.2310 -0.0065   4 
2013.043.22:32:46.50#fivpt#laterr   0.00792  0.0221  0.0778  0.0473  0.0008   0.0810 

Where the latfit and laterr lines refer to the fitted paramaters and their errors respectively.

  • Offset is pointing offset in deg
  • Width is the width of the gaussian (deg)
  • Amp is the amplitude of the fitted Gaussian
  • C and M are the y-intercept and slope of the linear fit
  • E_code in latfit indicates the success (or not) of the fit. A negative number means the fit was unsuccessful a positive number (I think) is the number of iterations before a fit was achieved.

The Longitude (Azimuth) scan is done next and the output is similar:

2013.043.22:38:17.53#fivpt#lon   1  81493.  -0.3417    0.803  0.049 
2013.043.22:38:31.54#fivpt#lon   2  81507.  -0.2563    0.991  0.072 
2013.043.22:38:45.50#fivpt#lon   3  81521.  -0.1709    0.885  0.064 
2013.043.22:38:59.46#fivpt#lon   4  81535.  -0.0854    1.278  0.052 
2013.043.22:39:13.46#fivpt#lon   5  81549.   0.0000    1.441  0.078 
2013.043.22:39:27.49#fivpt#lon   6  81563.   0.0854    1.286  0.061 
2013.043.22:39:41.46#fivpt#lon   7  81577.   0.1709    0.925  0.068 
2013.043.22:39:55.50#fivpt#lon   8  81591.   0.2563    0.975  0.128 
2013.043.22:40:09.51#fivpt#lon   9  81605.   0.3417    0.999  0.078 
2013.043.22:40:09.51#fivpt#lonfit  -0.00320  0.1878  0.5616  0.9179  0.0010   7 
2013.043.22:40:09.51#fivpt#lonerr   0.01488  0.0384  0.0907  0.0447  0.0009   0.0899 

Note that the fit is done in Azimuth not cross-elevation so the pointing offset and width of the Gaussian should be scaled by cos(El) to get an offset in degrees on the sky. This is calculated for you and displayed next:

                                    Az          El      Lon_offs   Lat_offs
2013.043.22:40:13.21#fivpt#offset   210.7833    5.4745  -0.00320   0.02518  1  1 
2013.043.22:40:13.21#fivpt#xoffset  210.7833    5.4745  -0.00319   0.02518  0.01481  0.00850 1 1 

Where offset shows the offsets in antenna coordinates (Az and El) and xoffset in sky coordiantes (i.e. Az x cos(El)). It's the xoffset values that we want to look at. In the above, Az and El are the Azimuth and Elevation that the fit was done, Lon_offset is the cross-El pointing offset in deg and Lat_offs is the Elevation pointing offset in deg.

/home/www/auscope/opswiki/data/pages/operations/documentation/fivept_output.txt · Last modified: 2013/02/20 01:54 by Jim Lovell