NOAA tsunami buoys-DART surface buoys. Stennis Space Center, Mississippi, 2006. DART II became operational in 2005. A significant capability of DART II is the two-way communications between the BPR and the TWCs/NDBC using the Iridium commercial satellite communications system. The two-way communications allow the TWCs to set stations in event mode in anticipation of possible tsunamis or retrieve the high-resolution (15-s intervals) data in one-hour blocks for detailed analysis. DART II systems transmit standard mode data, containing twenty-four estimated sea-level height observations at 15-minute intervals, once very six hours. The two-way communications allow for real-time troubleshooting and diagnostics of the systems. The DART buoys have two independent and redundant communications systems. NDBC distributes the data from both transmitters under separate transmitter identifiers. NDBC receives the data from the DART II systems, formats the data into bulletins grouped by ocean basin and then delivers them to the National Weather Service Telecommunications Gateway (NWSTG) that then distributes the data in real-time to the TWCs via NWS communications and nationally and internationally via the Global Telecommunications System.