Unmanned Systems Technology 022 | XOcean XO-450 l Radar systems l Space vehicles insight l Small Robot l BMPower FCPS l Prismatic HALE UAV l InterDrone 2018 show report l UpVision l Navigation systems

32 Dossier | XOcean XO-450 Data overload The sensor operator’s presence highlights one of the fundamental limitations of satellite comms. Despite the increases in available bandwidth, sensors such as Simrad’s EK80 scientific echo sounder are outpacing them in the volume of data they generate. “We completed a seven-day survey recently in the Celtic Sea, and we collected 110 Gbytes of data. We’re not going to send that over a satellite link; the pipe is simply too small,” Ives says. “So we use the comms system to monitor the quality of the data being collected.” What is shown on the sensor operator’s screen is just a visualisation of the data being collected, and that is far smaller than the complete data set. It is still adequate though to provide a quality control overview to inform an experienced surveyor’s decisions about whether to change a ping rate or adjust the transmission power of the sonar, or to request that the USV repeats a particular section of the route. Carlisle says, “With the EK80 as an example, the remote desktop we are using for the live viewing of the screens needs just 10-20 kbit/s to maintain the connection. There are also options being developed to perform live processing of data onboard the vessel, and only transmit highly compressed ‘summary’ files.” That is easily within the capabilities of both satcom systems that XOcean offers with the XO-450 – Inmarsat’s 284 kbit/s Fleet Broadband service running on Cobham hardware, and the Iridium 128 kbit/s Pilot system – either of which can serve as the primary comms bearer or as the back-up. Inmarsat covers less of the globe from 70 º N to 70 º S, while Iridium covers from pole to pole but at lower data rates. As a third option, the company also offers Globalstar satcom equipment. All the comms systems have security features including industrial-grade virtual private networks and encryption, Ives emphasises, adding that they wanted to ensure a highly robust and secure connection with the vessel from day one for the main comms bearers and back- up systems. “You don’t want to have the front door heavily protected but the back door open,” he says. The wi-fi system is not used to communicate at sea, but has been included for use while the boat is alongside or on the trailer during commissioning or decommissioning. It enables an engineer to log in and download data or upload the software to run a new sensor that’s been attached. However, the need to send signals via satellites unavoidably introduces latency, which presents its own engineering challenges in persuading off-the-shelf systems to work in a high-latency environment. “We’re waiting milliseconds for connections, but that’s an eternity to a computer,” Ives says. “We’ve got to make the system understand that it could be waiting half or three-quarters of a second before it gets a response.” Potential problems include messages timing out repeatedly in a loop if the system doesn’t understand the environment it’s operating in, preventing upload of a file from the boat. The solution is to tell it to wait for longer. Detail improvements The differences between the prototype and the second boat are numerous but small and largely aimed at convenience. For example, the second boat has a power socket on the gantry to charge the battery in port without opening a hatch. The prototype has hatches on the stern that must be unbolted to give access to the hard drives; in the second boat the drives live under quick-release deck hatches at the bow. Also, internal reconfiguration of the centre pod has freed up space for extra fuel in the second boat, while moving the generator hatch to one side of the pod improves access for maintenance. The current engineering effort is focused on integrating new sensors, suggestions for which emerge from regular discussions. Selling the vessel to others to operate is not a priority, but it is something XOcean is considering for later as the business evolves. More immediately, having outgrown James Ives’ home, XOcean is on the cusp of moving to a small industrial unit nearby that has more space and easier access to the water. October/November 2018 | Unmanned Systems Technology The tubular aluminium superstructure is bolted to the hulls according to established boat-building practice. The small blocks on the deck are solar panel power cable terminals. (Courtesy of XOcean)