@alanboyle
The HiSAS syntheic aperture SSS on DSV’s Hugin is one of the best of such systems but the organisation of the mission, as described, didn’t appear to give enough resources to reviewing imagery produced by the HiSAS. Even if the Hugin’s CathX camera was unserviceable, a revisit using only the HiSAS should’ve been sufficient to confirm whether the target is, at least, an aircraft.
The story has legs, some miles left to run!