last update: July 31, 1998.
Vicky Kaspi

PMBIRDIE_SUMMARY

pmbirdie_summary is a program for use on zero DM .s. files produced by pmbirdie_hunter. Its job is to combine the .s. outputs for many/all pointings on a tape and create filters, written to .accu files, for use in interference rejection in pmfind. A sample .s. file viewed with pms_plot can be viewed here.

pmbirdie_summary should be called using the script pmbirdfiles .

Note that a successful run of pmbirdie_summary will result in the announcement of an IEEE flag enabled. This is a feature of the compiler. IEEE traps, by contrast, signal errors such as division by zero.



WHAT PMBIRDIE_SUMMARY DOES
UNDERSTANDING PMBIRDIE_SUMMARY OUTPUT



WHAT PMBIRDIE_SUMMARY DOES:

pmbirdie_summary was adapted from birdie_summary, though I have significantly changed some of the algorithms, particularly that for harmonic and fundamental id.

• It opens all .s. files, identifying "garbage" beams in the process. Those are noted in the file pm_bad_beams and are ignored.
  
  
• The zerodm candidates from the .s. files are sorted by s/n and those below the s/n threshold set by the input parameter snmin are thrown out. Note that the diagnostic output file "candidates" contains this list, helpful for debugging.
  
  
• The main search for harmonics is done and candidates are identified. The details of how this is done are complicated. Some diagnostic outputs, useful for debugging, can be found in files fort.51, 55, 76, 78. The algorithm involves two passes at the candidates list in order to identify spurious sub-harmonics introduced by the harmonic folding process as well as mis-identified fundamentals. pmbirdie_summary output to the screen will mention the number of filter candidates after each of these passes. Pass 2 should have fewer filters.
  
  
• Filters that match the input parameter requirement for number of occurences and s/n are reported to the PostScript output. Note that for candidates that occur in a single beam repeatedly, or for candidates that appear in only one pointing, the threshhold for the number of occurences required to flag it as a birdie are different than the parameter nocc. In particular, for candidates in one beam only (Nbeam=1) if the number of occurences is greater than 4 it is called a birdie. For candidates occuring exclusively in one pointing (Nptg=1), if more than 4 occurences are found, it is called a birdie. For candidates occuring in more than one beam and more than one pointing, the input parameter noccur is the threshhold.
  
  
• The .accu files are reopened and filters that are appropriate for each file are written.

UNDERSTANDING PMBIRDIE_SUMMARY OUTPUT:

pmbirdie_summary writes filters to accu files for use with pmfind. It also provides diagnostic output in the form of a PostScript file that has name e.g. PM0017_b_14_38.ps for tape PM0017 pointings 14 through 38 in beam mode. Here is a sample. Here is a synoposis of the output:

• First page:

  • Greyscale showing a low resolution unfolded modulation spectrum for all pointings (in beam mode) or all beams (in pointing mode). Note that the spectrum has had standard filters zapped, ie the spectra that are plotted are those produced by pmbirdie_hunter after the zapping has been done. The example is beam mode (as stated on the top). Within the horizontal lines separating the pointings are the spectra for all 13 beams.
    
    
  • Note that data for pointings 24, 25, 26, 27 are entirely absent; they were deemed to have too much interference by pmbird creates.
    
    
  • Note also that pointing 28 has two missing beams; those beams were either absent for some reason or bad (in this example they were absent).
    
    
  • Vertical stripes indicate signals common to many beams/pointings. In this example, there is a strong signal at 62.5 Hz with many harmonics (the highest at 1875 Hz).
    
    

• Second page:
  

  • Total number of blocks is the sum of the number of blocks per beam as read from the accu file.
    
    
  • Total number of beams is the total number of .s. files read in.
    
    
  • Start beam info is for the first .s. file read in. In this example it is pointing 14, beam 1.
    
    
  • End beam info is for the last .s. file read in. In this example it is pointing 38, beam 13.
    
    
  • "dummy" beams are beams for which pmbirdfiles found no .s. file. Dummy beams are necessary to allow pmbirdie_summary to properly organize the .s. files in the directory.
    
    
  • "garbage" beams are beams that exist but are corrupted. Either the .s. file or the .accu file may be corrupted. Garbage files are ignored and are noted in the file pm_bad_beams.
    
    
  • Initial list of filters: these are the filters in the file $searchdir/bhbird read in by pmbirdie_hunter . Note that the Deleted Frequency Range is a synopsis of ALL input .s. files -- it shows the max and min of the range of deleted frequencies. Individual .s. files usually have had much narrower ranges deleted. Note also that the deleted range may sometimes exceed the input range (never by more than a spectral bin.) This is because of the quantized representation of the modulation spectrum.
    
    
  • Output filters: here is what the columns represent:
    
    
    • Peak Freq: peak frequency of the fundamental
      
      
    • Frequency Range: the frequency range this birdie (and its related harmonics, back extrapolated) were found in. Note that the range may not be symmetric about the peak.
      
      
    • Nharm: harmonic number of the highest harmonic found. Note that for a harmonic to be identified, it must be less than 10 harmonic numbers larger than the highest one found previously. (e.g. if only the fundamental has been found, the 11th harmonic will not be identified.).
      
      
    • max s/n: maximum s/n found for the fundamental or any of its harmonics.
      
      
    • Noccur: number of .s. files in which the fundamental or any of its first 16 harmonics appears. This is also the number of .accu files to which this particular filter is written.
      
      
    • Nbeam: number of unique beams the fundamental or any of its first 16 harmonics in which was found.
      
      
    • Nptg: number of unique pointings the fundamental or any of its first 16 harmonics in which was found.
      
      
    • Note: if there are so many filters that pmbirdie_summary cannot fit them all on one page, pmbirdie_summary prints a warning message and proceeds. The true number of filters gets written to the ascu files, however, only the list in the postscript output is affected. Hopefully this will happen rarely.

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