The North Polar Spur and Aquila Rift
  Soft X-ray intensity at 0.89 keV along the North Polar Spur is shown to
follow the extinction law due to the interstellar gas in the Aquila Rift by
analyzing the ROSAT archival data, which proves that the NPS is located behind
the rift. The Aquila-Serpens molecular clouds, where the X-ray optical depth
exceeds unity, are shown to have a mean LSR velocity of v=7.33 +/- 1.94 km/s,
corresponding to a kinematic distance of r=0.642 +/- 0.174 kpc. Assuming a
shell structure, a lower limit of the distance to NPS is derived to be 1.01 +/-
0.25 kpc, with the shell center being located farther than 1.1 kpc. Based on
the distance estimation, we argue that the NPS is a galactic halo object.
