Where in the Milky Way is the North Polar Spur

The NPS is a region of strong diffuse Xray emission extending in an arc froml,b 25deg,10deg to 330deg,75deg. Conventional wisdom says that the NPS is thelimbbrightened edge of the Loop I superbubble, roughly centered on, and likelypowered by the ScoCen OB association, placing it at a distance of 100200 pc.However, it has also been seen as a supershell centered on the Gal. center, andthe implications for the plasma and energy involved are extreme. We propose todetermine the location of the NPS using a series of overlapping observations ofthe southern terminus. Comparison with the Gal. distribution of Xray absorbingmaterial will allow us to determine if it is absorption bounded, and by whichISM features, thus revealing its distance. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]