Uncrewed Systems Technology 049 - April/May 2023

22 In conversation | Noel Heiks species that grow at exponential rates that power companies are not used to dealing with, then it gets on a powerline and you have a fire,” she says. “Doing that on a regular basis using UAVs though means you don’t have the safety issues associated with manned aircraft, and you can cover long distances – 80 to 100 miles at a time.” In addition to the AI software, one of the challenges with implementing this capability is the close integration required between the payloads and the UAVs. Heiks emphasises the importance of standardising the footprint of the receptacle in which the payloads are to go, on which Censys has worked closely with payload vendors to achieve. “So you can put a variety of different gimbals, Lidar systems and so on into the standard platformwith standard connectivity.” Monitoringmethane Environmental monitoring is a growing market for UAV operations, and laser-based sensors that can detect greenhouse gases, particularly methane, look to provide a useful new capability. Heiks explains that some US state governments have been tasked with tracking down ‘orphaned’ oil wells that need to be capped, because about 20% of all 2.5million of themare leakingmethane. “That was one big issue we could see coming up about 18 months ago, so we started test flights over areas known to be leaking methane, a lot of them over landfills,” she says. The detection technique used is the well-established tuneable differential laser absorption spectroscopy. The challenge lies in developing a reliable, accurate, compact and lightweight system for UAV deployment. In the initial trial implementation, the system aboard the UAV aimed two laser beams at the ground, one of which was tuned to a wavelength that is absorbed by methane and the other which was not, to act as a control. “If methane is there, light from the tuned laser is absorbed and the amplitude of the light reflected back decreases. But if the second laser beam is also attenuated then there is no methane,” she says. “If there is a difference in absorption between the two wavelengths though then you definitely have methane.” Up close and personal “Usually, spectroscopy is done with small systems in which there is a chemical under test, a laser and a receiver all in one small unit. Now imagine the problems you have when your test sample is a long way from the sensor. “You have a lot of attenuation fromthe reflecting surface. There is a lot of scatter fromgrass or the ground, so you have to pick outminute signals coming back. You must be up close and personal to do this sensing – hundreds rather than thousands of feet above the sensing surface.” Heiks adds that the accuracy of this experimental system in mapping methane emissions in the target area was not as good as Censys wanted for an operational April/May 2023 | Uncrewed Systems Technology Sentaero UAVs will combine sense & avoid technologies and remote ID in addition to laser sensors and the ability to map sources of greenhouse gas emissions