Testing the byumap pointing pattern

30apr10: testing the pattern on J0745+101

• lband wide receiver, 1405 MHz, linear pols.
  
• Record data with interim correlator: 1 second integrations, 6 MHz bandwidth, 9 level sampling.
• Source: J0745+101, 3.55 Jy
  
• map grid:
• 13x13 with central pixel on  (7,7) on source (counting from 1).
• 1 arcmin step in cross el, za. This is about 1/3 of a beam width.
  
• 4 second integration per pnt
• byu computer emulator
• A program was used to emulate the byu computer. It received the requests from the byumap routine and then replied with cmd ok.
  
• The emulator also wrote each request to disc for debugging purposes. The output line had the ast time prepended to it.
  

byumap calling sequence:

• byumap ra dec zaOffAmin azOffAmin stepAmin secsPnt focus off_steer firstZaStrip firstAzPnt
• ra, dec: the  J2000 position for center of map.. format: hhmmss.s ddmmss.s
• zaOffAmin, azOffAmin: the great circle offset from the center of the grid to the center of the outermost point of the grid. The sign of the offset specifies witch edge of the grid you start on. zaOffAmin < 0 starts at the  za lower than the source, zaOffAmin > 0 starts at a strip with za greater than the source.
  
• stepAmin: The  step size in za and cross el in great circle arc minutes.
• secsPnt: the time to sit on each point after the byu computer has acknowledged that it has started to take data. The telescope actually waits an additional second before it tries to move to the next source to make sure the integration has completed.
• focus: focus offset in inches
• off_steer: 0 no offs, 1- off at start strip, 2-off at end strip, 3 - off at start and end. Offs are -1 deg (off_steer=1,3) and +1 (off_steer=2,3) along the az strip.
  
• firstZaStrip, firstAzPnt: Start the mapping at a grid point that is not at the start. This is useful if you are resuming a partially done map. count from 1.
  
• Notes:
• zaOffAmin,azOffAmin,Astep specify the map dimensions.
  
• The sign of zaOffAmin,azOffAmin specifies which side of the original map you start on.
• firstZaStrip,firstAzPnt let you start at a strip,az point other than the first (using the zaOffAmin,azOffAmin, Astep definition of the original map).
• The grid always has an odd number of azpnts, za strips to guarantee that the central point is always on source.
• The tcl code used for the call  was:
• set bmw 3. ;# set beamwidth to 3 arc minutes
  set azOffAmin [expr -2*$bmw] ;# set az off to -2 beamwidths
  set zaOffAmin [expr -2*$bmw] ;# set za offsets to -2 beamwidths
  set stepAmin [expr $bmw/3.] ;# step 1/3 of a beam width
  set secsPnt 4
  set focus 0
  set firstZaStrip 1
  set firstAzPnt 1
  set ra 074533.06 ;# J2000 ra hhmmss.ss
  set dec 101112.70 ;# J2000 dec ddmmss.ss
  byumap $ra $dec $azOffAmin $zaOffAmin $stepAmin $secsPnt $focus $firstZaStrip \ $firstAzPnt

Debugging output:

• Outputting the strings sent to the byu computer.
• This file holds the output sent to the byu computer for the grid.
• The first part of the file is just document ion that was added later.
• The time stamp at the beginning of each output line was added before writing to the log file (it was not sent to the byu computer emulator).
• See the communications section above for the parameters for each command.
• Debug output from byumap routine
  
• This info is output by the byumap routine for debugging.
• Start of each strip:
• Start strip: 0 azOff:-6.00 zaOff:-6.00 tm:17:19:53
• The routine output is counting the strip number from 0 to 12
• Azoff,zaOff are the offsets for the start of this strip (in arcmin).
• tm:hh:mm:ss is the ast start time for this strip.
• Points in each strip.

• azPnt  azOff tmSt  tmNextMove tmWaiTrk   raPnt   decPnt &$
         Amin  SecsM SecsMidnite  secs   hhmmss    ddmmss
  
     0   -6.00 62409      62414  15.0039  74540.4  101931.3

• This shows the info for each point of the strip.
• azOffAmin : azimuth offset this point in strip
• tmSt SecsM: seconds from midnite ast when byu computer said it was taking data.
• tmNextMove: seconds from midnite ast when the telescope is going to start moving to the next spot. In this case it is 5 seconds after start of data taking (4 seconds of data + 1 second of slop).
• tmWaitTrk: Time in seconds from telescope move request to when byu computer says it is taking data.
• The wait time at the start of each strip is longer than the time between points in a strip.
• Timing:
• 4 second integrations:
• 13x13= 169 point map took 28min,50 secs or 10.2 secs/point.
• The move times depend on how far the azimuth has to move (since it changes with the sine of the za).

The map data:

• Top: the 13 total power strips over plotted vs az offset. The data has been normalized to Tsys.
• Bottom: The 3 za strips about the center of the map (6,7,8 counts from 1).
• The red strip passes thru the center
• The data has been normalized to the peak value of the source
• The blue dotted lines show the fwhm for the red line.

• The colored contours are spaced by 3db. The magenta ring at 5amin is the first side lobe at -15 db.
  

Summary:

• A 13x13 point map with 4 second integration took 1730 secs(28min,50secs)
• The times gave 10.2 secs/pnt averaged over the entire map. The times included:
  
• 3-4 seconds move time for points in the strip. This varies depending on the az move distance needed (it changes az 1/sin(za)).
  
• about 12 seconds move time for the first point of each strip.
• 4 seconds of integration time
• 1 sec extra after integration for byu computer to complete.

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