Reflections on sea rescue
Finding people lost at sea could soon be lot easier, thanks to work done for the US air force by an inventor in Stamford, Connecticut, US. Although Gerald Falbel's patent was filed to help search for downed military pilots, it can be used equally well for finding shipwrecked sailors or airline passengers in life-rafts.
The downed pilot wears a helmet that carries a large glass hemisphere, similar to a camera fisheye lens, on the top. This sits over a reflector, which catches light from every direction and reflects it back in the direction it came from – much like a cats-eye road marker.
A spotter plane flying high over the rescue area – at about 10,000 feet – sweeps a laser beam across the water, say East to West. It then rapidly retraces the beam's path, before starting a new sweep slightly to the North. Each sweep takes just 1 second, meaning a path tens of miles long can be scanned in just a few minutes.
If the beam hits a cats-eye helmet it bounces straight back, to be registered by a camera sensor and recorded as a hit. Although there will inevitably be false reflections, from stones or water glints, they will not show up from the same place on a retraced beam sweep, so can be safely ignored.
The laser is also pulsed to help the sensor distinguish a genuine hit from reflected sunlight – sunlight has no pulses.
More detail on the high-speed air sea search system is available via the link below.
