Clocked at M 1.44, does that sound feasible
They leave them on all the time going fast. While I don't know the exact spec, from observation TAAAAAAATS and the previous IRDS dropped ground speed readings in excess if 1200(?) knots and the track symbol goes into a 'coast' mode. ATC radar does not display Mach number due to obvious reasons of calculating it. Based on that at sea level it could track up to around Mach 1.8 or so at sea level assuming the aircraft could do it. They do it east of the coast in various places.