Scintillation of PSR B1508+55 – the view from a 10 000-km baseline

We report on the simultaneous Giant Metrewave Radio Telescope (GMRT) and Algonquin Observatory (ARO) observations at 550-750 MHz of scintillation PSR B1508+55, resulting in a $\sim$10,000-km baseline. This regime measurement lies between shorter few 100-1000~km baselines earlier multi-station much longer earth-space baselines. measure cross-correlation coefficient $0.22$, offset from zero time lag due to $\sim 45$~s traversal pattern. The 135~s is $3\times$ longer, ruling out isotropic as well strictly 1D scattering. Hence, low indicative highly anisotropic but 2D common detected baseline confined delays $\lesssim 1 \mu$s, suggesting that this correlation may not be associated with parabolic arc GMRT. Detection pulsed echoes their direct imaging Low Frequency Array (LOFAR) by different group enable them distance 125~pc screen causing these echoes. These previous measurements, alongside our observations, lead us propose there are least two scattering screens: closer 125 pc GMRT, further beyond GMRT-ARO advance hypothesis 125-pc partially resolves speckle images leading loss coherence dynamic spectrum, explain coefficient.