METEOROLOGISTS it sometimes seems, retain a rather loveable fascination with the little toys they used to have as children, and are constantly on the lookout for bigger ones to play with toys that may, with a little luck, also help them to predict the rain with greater confidence. You may remember, for example, reference in Weather Eye some years ago to balloons that it was hoped might circle the earth ad infinitum, trapped at a particular level by their own carefully calculated buoyancy, and condemned for ever to send data back to Earth to satisfy meteorologists' never-ending thirst for weather observations.
They never really quite caught on. Neither did the solar-powered model aeroplanes with a somewhat similar roving brief, nor the ultra-intelligent drifting ocean buoys that were intended to lock on to a satellite navigational system, and continually trim their jibs and topsails to allow them to retain, or sail back to, their pre-assigned positions. The latest innovation of this kind is Halrop.
Halrop stands for High-Altitude Long-range Observing Platform, and it is essentially an unmanned and remotely-controlled airship 150 metres long, with no internal source of power. Instead, it is fitted with two electric thrusters that derive their energy from a large receiving antenna fitted underneath the aircraft, which converts microwave energy into electrical power. The microwave energy, in turn, come from a large parabolic dish upon the ground, which projects a multi-kilowatt beam upwards in the direction of the airship.
The idea is that the thrusters will receive enough power in this way to keep the aircraft in position against whatever winds may be aloft, fixed indefinitely over a precise spot at, say, 20 km above the ground. This is not a trivial task, because the beam of energy from the transmitter diffuses and attenuates with height, so the receiving antenna can only capture a small fraction of the power transmitted. And the more powerful the transmitted beam, the greater the tendency for any organism in the way to suffer the same fate as if enclosed in a domestic microwave.
The Japanese inventors, however, are confident that these and any other problems can be overcome. They say that Halrop will be able to carry out many of the tasks now performed by satellites at a fraction of the cost, providing useful telecommunications links, and transmitting back to earth for use by weather-forecasters frequent high-resolution images that will be much better than any available at present, because of the lower attitude of the camera.