We request HSA observations at four di#erent frequencies of the giant FR I radio galaxy NGC315. The tremendous
sensitivity of the HSA should allow us to obtain detailed images of the jet and counter-jet emission found in previous
VLBA images. NGC 315 is one of the closest FR I radio galaxies and therefore one in which we get the best linear
resolution. Moreover NGC 315 is one of the few sources where a jet acceleration has been measured in the inner 10
mas from proper motion and from the jet counter-jet brightness ratio. New data will allow a better study of the jet
and counter-jet emission necessary to confirm the jet acceleration, and the trend of the jet velocity. We think that
requested observations will help to determine the region of the jet in which the bulk of acceleration take places, and
will allow us to discuss the jet dynamics. Moreover new observations will allow a detailed spectral index study along
the jet and counter-jet to investigate radiation losses and the possible presence of regions where relativistic electrons
are locally reacelerated. The presence of a di#erential jet transverse velocity should be well visible from detailed
images of the jet (and counter-jet). |