Active Duty ping.
(I know... Debka)
This thing makes no sense unless the idea is to attract all sorts of enemy attack subs and store their signatures. That’s what the ASW ships are for (as well as to make sure no one tries anything foolish). Perhaps the Donskoi is being put to sea to shake out hidden problems and someone decided to take the opportunity to combine diplomatic, technical and intelligence missions all in one package. After the Donskoi returns it prepares for a cruise with the latest data on attack subs and is ready to take a three month hide.