SeaTrac SP-48 USV | Digest to have control over development and modifications to any part of the system, ensuring they could make changes to accommodate customer demands and move towards certifications. The USV’s standard, marine-grade GPS provides a primary feed of satellite navigation signals into the autonomy control system, while a backup GPS is also installed for redundancy if the main system drops. A more advanced, high-accuracy GNSS can be installed for precision survey missions, such as multibeam sonar mapping. “For missions like that, we can add in a Trimble Applanix INS and high-accuracy differential GPS to get very precise location data,” Boeschenstein says. As a final situational awareness aid to the operator, four 1080p, continuous zoom cameras sit on the mast, although many other solutions can be installed, such as Teledyne FLIR thermal imagers for surveillance in low-visibility conditions (an M364C camera from that company having previously been integrated on an SP-48 for work with Task Force 59, the US Navy’s premier uncrewed r&d fleet). Ocean data As well as those cameras, a wide array of payloads have proven compatible with the USV and valuable to SeaTrac’s end-users. For instance, the first multibeam sonar that the team integrated was Norbit’s iWBMS H-N, a widely used system for high-quality seafloor mapping at an efficient power draw, which suited the USV’s form factor closely. “We’ve also used the R2Sonic 2020 multibeam and gotten good data with that one too. We are quite agnostic to echosounders, so long as they physically fit our moon pool and their overall SWaP makes sense within what our USV can offer,” Boeschenstein says. The moon pool offers a cylindrical volume with a maximum diameter of roughly 10 in, but SeaTrac is open to customising sensor housings to fit payloads elsewhere on the USV. SeaTrac has integrated Teledyne Marine’s Workhorse Monitor ADCP as its primary tool for current-measuring missions, although Nortek’s Signature 1000 has also been operated for some customers. “We have also had Seaview Systems’ SVS-603HR wave-height sensor working onboard, which we used to measure things like maximum wave heights and periods of waves,” Boeschenstein adds. Additionally, AML Oceanographic’s water-quality measuring sondes have been used, particularly the AML-3, which judges depth and two other parameters of the end-user’s choosing, such as turbidity, pH or chlorophyll. These have sometimes been hardmounted to the hull, but nowadays the team will more often integrate them into a specially made winch, designed and engineered by SeaTrac, primarily for running sound-velocity profiling simultaneously with multibeam echosounder work. “The winch uses a non-powered tether to keep it simple, as a tether can be run much longer if you aren’t running power and comms through it, and it also means we don’t run into reliability issues with things like slip rings that can break,” Boeschenstein explains. “AML also supports a wireless charging solution that we use. When the USV completes its cast, the winch hoists the sonde up to proximity with the charging emitter, we collect the data it has amassed over wi-fi and the sonde gets recharged while dumping data, so it’s ready for another mission without any technicians needing to physically handle anything shore side during that process.” Data links Given that the USV may spend multiple months at sea per mission, data-link security via a plethora of comms systems is paramount. “As they say in the navy, two is one, and one is none, so redundancy is everything for communications as far as we’re concerned, because you can’t predict when something will go down,” Boeschenstein says. “The base boat comes configured with a 916 MHz data link for LOS connections, and that’s primarily used with a handheld GCS that we first use to drive the boat off a trailer, away from the dock, and potentially through a busy channel for deployment or recovery. But, for the rest of the way, it is critical that the USV can work on its own without needing people to intervene.” 55 Uncrewed Systems Technology | December/January 2025 Many echosounders and other marine-survey sensors have been mounted and used in the SP-48’s moon pool, although payloads can be integrated via custom housings across the hull
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