12 August 1998
During the Cold War, the US military developed a method of sending data by bouncing radio signals off meteor trails. Every day more than a million specks of dust enter the Earth's atmosphere from deep space and burn up, leaving trails of particles. Amateur radio operators had noticed in the 1920s that they could bounce signals off these trails. Although the trails last only a few tenths of a second, there are so many that at any given time there are usually enough for a ground-based transmitter to work with.
The high cost of developing the "Meteor Burst" system meant that the project was cancelled when the Cold War ended. The scientists who worked on the system left to set up a Seattle-based company called StarCom Technologies, which has developed a civilian version as a cheap alternative to satellite systems.
StarCom transmitters continually send probe signals to test for reliable reflections. When a return signal is sensed, the transmitter sends out a rapid burst of digital data at frequencies between 40 and 50 megahertz that can be picked up over a wide area. The data transfer rates are low, up to 20 kilobits per second, and transmission time is limited to a few hundred milliseconds per meteor, but this is sufficient for uses such as monitoring vehicles' positions.
This is the purpose for which the system has been tested by a private ambulance company, American Medical Response (AMR), which ferries patients all over Washington State and Oregon. After successful tests of prototypes over the past six months, the company this week began fitting StarCom transceivers to a quarter of the 80 vehicles it uses to serve Seattle and the surrounding area.
All the ambulances are fitted with a global positioning satellite receiver as well as a StarCom transceiver, allowing them to continually report their position back to AMR's Seattle control room. The system enables the company to keep track of where an ambulance is and whether it has a patient on board.
"We crosschecked the StarCom data with our own computer mapping and feel pretty confident that it is hitting the mark," says Greg Sim of AMR.
StarCom now wants to hide transmitters in vehicles that will automatically send out a signal if the vehicle is stolen. The system could also be used to interrogate measuring instruments in remote areas.
"We are using the satellites which nature provides for free," says Guy Rosbrook, StarCom's chief executive and a former Meteor Burst scientist. "There are so many meteors that you can regard the sky as a wide-area cracked mirror."
Author: Barry Fox
New Scientist issue 15th August 98, page 17