  We report on an effort to extract and monitor interstellar scintillation
parameters in regular timing observations collected for the NANOGrav pulsar
timing array. Scattering delays are measured by creating dynamic spectra for
each pulsar and observing epoch of wide-band observations centered near 1500
MHz and carried out at the Green Bank Telescope and the Arecibo Observatory.
The ~800-MHz wide frequency bands imply dramatic changes in scintillation
bandwidth across the bandpass, and a stretching routine has been included to
account for this scaling. For most of the 10 pulsars for which the scaling has
been measured, the bandwidths scale with frequency less steeply than expected
for a Kolmogorov medium. We find estimated scattering delay values that vary
with time by up to an order of magnitude. The mean measured scattering delays
are similar to previously published values and slightly higher than predicted
by interstellar medium models. We investigate the possibility of increasing the
timing precision by mitigating timing errors introduced by the scattering
delays. For most of the pulsars, the uncertainty in the time of arrival of a
single timing point is much larger than the maximum variation of the scattering
delay, suggesting that diffractive scintillation remains only a negligible part
of their noise budget.
