44 customer payloads can be commsindependent. Hence they can connect just mechanically and electrically to the UAV, with separate data links from the Zephyr’s. “Of course, you’ll generally want optical payloads in the nose, but things like comms relays could be mounted anywhere,” Tyler says. Generally, Briggs adds, “Customers often get a bit worried when we give them a weight budget and their payload exceeds it. But we have ways of stripping the casings off payloads and adding lightweight insulation and heat transfer materials, along with other steps as part of our payload integration service.” AALTO’s own in-house payloads include its previous OPAZ developments in live 4K video capture and streaming, as well as newer ones relating to connectivity. At the moment, the company’s payloads can capture EO imagery accurate to 18 cm/pixel and IR images at 70 cm/pixel at cruising height. In addition to demonstrating D2D capabilities in the past – with the ability to cover 7500 km2 of ground while in flight, equating to 250 terrestrial towers – AALTO will be showcasing and demonstrating comms relay payloads as mature D2D solutions in flights over the next year. “We’ve flown other payloads including IR cameras, Lidars, air-to-air optical comms systems as well as laser comms for air-to-air, air-to-ground, and air-toorbit,” Tyler comments. “Lasers present a huge opportunity in the future for high-bandwidth comms, and there are now good targeting systems for beaming directly from the ground to aircraft. Their full commercial readiness is still some way off, but we’re also starting to look at lasers for delivering energy and replenishing the Zephyr’s batteries. “We’re not yet developing those inhouse, but a year ago we weren’t even in the comms business. Since then, we’ve demonstrated airborne D2D radios – D2D being something even Starlink can’t do yet – so we’re interested in bringing in new ideas of what we could fly on the Zephyr one day.” Landing To end a mission, the Zephyr glides down to its recovery runway (tarmac is preferred but dirt is acceptable) and conducts an automated belly landing, stopping within 5-10 m of touchdown. Its lightness and low near-ground speed minimise its inertia, so a technician could stop the HAPS with one hand if needed. Descent takes about 18 hours – a while longer than ascent – owing to the Zephyr’s gliding efficiency. Although this could be accelerated using extra servos to pitch harder, AALTO sees these as unnecessary weight as they would only be used for the final hours of a 200-day flight. This is also why Zephyr has no landing gear or wheels. Once landed, the HAPS is hoisted from the ground onto a trolley, taken inside a containerised workshop, inspected and dismantled for shipping. “As well as setting up SOCs, we’ll also have a worldwide network of ‘AALTOports’ in the future, with runways, personnel and facilities for all landing and post-recovery tasks,” Tyler says. “Between SOCs and AALTOports, we’ll also plan out global ‘sanctuary areas’ away from airways and populations where we’ll terminate a HAPS if it suffers a fundamental issue or can’t re-establish a data link. And if we are coming down, we squawk 7400 to ATC from our transponder – that’s now globally accepted as the uncrewed aircraft issue code.” If a fire breaks out at a GCS or AALTOport, and the crew does not have time to hand control to another team, the crew members can send it to a safety waypoint, and the craft can then set and follow up to over 200 further waypoints while waiting for its next order or landing clearance. It also has numerous time-based safety actions, such as calling a specified backup GCS and team after 30 minutes of losing a link with its operators to establish a new satcom link. Data links For LOS comms and telemetry including high-rate video streaming within a second of delay, the Z8 uses radios designed to operate at UHF (300 MHz to 3 GHz) and S-band (2 to 4 GHz). These work at around 10 Mbit/s until ranges of 150 km between the HAPS and GCS are exceeded. “Our BVLOS and LOS links can be separated,” Tyler says. “We could December/January 2024 | Uncrewed Systems Technology UHF and S-band links provide LOS monitoring between the HAPS and ground crews
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