[Isocops] Fwd: The black swath

[Nathan Schwadron]

Begin forwarded message:

> From: "Maher A. Dayeh" <maldayeh at swri.edu>
> Date: November 28, 2011 1:56:32 PM EST
> To: Nathan Schwadron <nschwadron at guero.sr.unh.edu>, "DeMajistre, Bob" <Bob.DeMajistre at jhuapl.edu>, "Maher A. Dayeh" <maldayeh at swri.edu>
> Subject: FW: The black swath
> 
> Hi Nathan,
> 
> After accounting for the survival correction, we are having a black swath in map2, it is pretty narrow (6 degrees, half orbit) and likely an artifact from the map construction. Adding that we do not cover the full sky (since we miss an orbit in every map). 
> Please see below for more on this (Bob’s explanation). I would like to discuss this briefly today.
> 
> Thanks,
> Maher
> 
> 
> 
> ------ Forwarded Message
> From: "DeMajistre, Bob" <Bob.DeMajistre at jhuapl.edu>
> Date: Wed, 23 Nov 2011 13:15:27 -0500
> To: "Maher A. Dayeh" <maher.aldayeh at swri.org>
> Subject: The black swath
> 
> OK, so the code is doing exactly what it’s supposed to do, unfortunately.
> 
> Orbit 34 sits right on the edge of a longitude bin. When we turn on the transport to the termination shock (using surd=), the code looks up the survival probability and uses the analytic expressions to find the energy loss and deflection angle. The deflection angle for this orbit comes out to about 0.2 degrees. With the weighting scheme your using, that 0.2 degrees moves the contribution to the other side of the bin boundary, effectively zeroing it’s contribution in one of the bins. 
> 
> I got rid of the effect by just forcing the deflection angle to zero in the code. 
> 
> We told ourselves that such small change in angle shouldn’t change the data – but with the binning scheme being used it looks like it does. This is clearly binning artifact – really an edge effect (it only shows up because the effective exposure time goes from a finite value to zero).
> 
> Going on from here - 
> you could present the maps as they are, explaining the change results from the combination of the deflection angle and the binning scheme.
> you could select another binning/weighting scheme (I haven’t played with these, so I don’t have a recommendation)
> You could adjust the binning intervals, say slide all the bins by 1/2 degree. This may just move the problem around
> You could add another orbit (either at the beginning or the end will work (I like this option the best).
> I could disable the deflection angle correction (I like this the least).
> 
> Bob 
> 
> 
> 
> ------ End of Forwarded Message

Nathan Schwadron
n.schwadron at unh.edu

University of New Hampshire
Morse Hall - Room 353
8 College Road
Durham NH 03824
USA

(603) 862-3451



-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.sr.unh.edu/mailman/private/isocops/attachments/20111128/858146cf/attachment-0001.html 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: SC_Map2_1.74.png
Type: image/png
Size: 59705 bytes
Desc: not available
Url : http://lists.sr.unh.edu/mailman/private/isocops/attachments/20111128/858146cf/SC_Map2_1.74-0001.png