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Review Committee Meeting Monday 17 December 2007 08:00 Pacific / 11:00 Eastern

Minutes: Monday 17 December 2007 08:00 Pacific / 11:00 Eastern

Agenda and Contact Info


  1. Review of BurstMDC Simulation
  2. A.O.B.

Contact Info

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  1. Review of BurstMDC Simulation
    • From last time: Jolien checked getifo convensions for GEO. Here is the discussion:
      Sorry, the arm that points NW is what we call the north arm.
      On Nov 28, 2007, at 18:19, Jolien Creighton wrote:
      Hi Martin
      This *almost* answers my question.  But I am not absolutely
      certain which is the "North" arm since both arms point somewhat
      Northish.  Is the North arm the one that goes NW or the one
      that goes NE?
      Here's the map I'm looking at:
      Sorry to be obtuse -- I'm pretty sure I know what you mean
      (but it is my job to be absolutely sure).
      On 27 Nov 2007, at 12:00, Martin Hewitson wrote:
      Hi Jolien,
      Our definition is that h(t) goes positive for decreasing length of the north arm. Does that answer your question?
      On Nov 26, 2007, at 21:34, Jolien Creighton wrote:
      Hi Martin
      I just want to double check a sign convention issue about GEO h(t).
      I know that the GEO arms don't make right angles, but they
      do roughly and suppose that Arm 1 and Arm 2 are taken so that
      Arm 1 cross Arm 2 points roughly up (rather than down).  Then is h
      defined (roughly) as
      	h = [(Length of Arm 1) - (Length of Arm 2)]/(Average arm length)
      I am principally concerned about an overall sign that could happen
      if we swapped Arm 1 and Arm 2 compared to the way you use them when
      you define h.
      To recap: look at the satellite image of GEO [ HTML ] The 'North' arm is the one that points North-West. When this arm shrinks, h goes positive. Let's call the other arm the 'East' arm. Since 'East' cross 'North' is 'Up' the convention agrees with that used by getifo and LIGO-T010110 [ PDF ], but is flipped compared to the Excess Power paper. Everything seems correct here.
    • Well known bug on line 22 of randomangle -- x = cos(theta) should be uniform in range [-1,+1] -- "found". This has been corrected, but we have not yet seen corrected code.
    • Note: rand and randn use different seeds. Not an issue for this code since only rand is used.
    • Line 86 of setexternal: (i) OPTIMAL should mean that the source is in the direction of V cross W, not set by latitutde of detector (since detector is not tangent to Earth) -- this is a small effect; (ii) CODEC is perhaps not a great term -- it is the cosine of the co-declination -- a different term should be used.
    • Line 113 of setexternal: (i) Again, OPTIMAL should mean that the source is in the direction of V cross W, not set by latitutde of detector (since detector is not tangent to Earth) -- this is a small effect; (ii) Note that if x is OPTIMAL and phi is not then x might not be optimal for that phi! Not clear what it means for one to be optimal while the other is not....
    • Line 137 of setexternal: Discussion of what psi should be chosen for optimal. Decided that psi=0 should be defined as "optimal" -- that is, for a linearly polarized wave, only the h+ component is injected if everything is set to "optimal". This agrees with other conventions used. Check that this is true: when x=OPTIMAL, phi=OPTIMAL, and psi=0, then injected waveform is the h+ waveform.
    • Line 183 of setexternal: Will need to be changed to be consistent.
    • Finished reviewing function pregenlist
    • General comment: hard to keep track of numerical mode numbers. These should be documented in help messages. Also would be beneficial if they were strings or enumeration constants instead so that it would be clear while reading the code what the modes mean.
    • Reviewed function ndraws.
    • Lines 205-210 of makelist: Why call setangles when pregenlist was called above? Make sure things don't go awry!
    • Finished reviewing makelist. Still need to review setangles, setinternal, and pickstime. Then go on to the actual computational part of Graven!
  2. A.O.B.: We will take a recess until the 7th of January. Patrick Sutton will call emergency meetings if necessary before then, and will run the meeting on the January 7.
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