Late last month we reported on a Notice of Proposed Rulemaking contemplating use of the 78-81 GHz band to detect “foreign object debris” at airports. If you feel moved to comment on that proposal, your deadlines have now been set: comments are due by February 10, 2012, and replies are due by February 27.
Devices will be used to detect runway debris; other applications are possible.
The FCC seeks comment on radar operations in the 78-81 GHz band, and in the meantime, has granted a waiver for limited use.
There has been a lot of regulatory interest lately in radar devices above 75 GHz, up in the “nosebleed” portion of the spectrum. Back in 2009, the FCC considered, and later granted, a waiver to allow the Atlanta airport to use 77-76 GHz radars to track aircraft and vehicles on the ground. The beginning of 2010 saw a proposal to use 78-81 GHz to measure the levels of substances inside large industrial tanks; there, too, the FCC granted a waiver, while a rule change is still pending. Last May, the FCC proposed to relax the rules for vehicle radars at 76-77 GHz, which provide for automatic braking when the car senses an obstacle ahead. That rule, too, is still under consideration.
Now the FCC has revisited the airport environment, with a proposal to authorize 78-81 GHz radars to detect “foreign object debris,” or FOD – apparently a term of art in the airport business. We are all in favor of FOD detection, remembering that a stray piece of metal on the runway, dropped from an earlier plane, tripped up an Air France Concorde in 2000 at the cost of 113 lives. Apparently aircraft shed parts more often than most of us realize. Other common forms of FOD include misplaced tools, equipment and supplies, rocks and pavement fragments, luggage, and wildlife.
A close reading suggests the FCC is determined to approve FOD radars. But it is not sure how: whether to authorize 78-81 GHz radar on an unlicensed basis, like cordless phones, or under license, like taxi radios. Another question is whether to restrict the band to use at airports, or to permit other applications as well. A third question is whether radar users should have to coordinate their operations with others who share the band.
All of these questions turn in large part on the need to protect radio astronomy from interference. Radio astronomers have a primary allocation across most of the band, which they use to identify molecules in remote stretches of space. The good news is that radar signals at these frequencies tend to form narrow beams and do not propagate well, thus cutting the risk of interference. On the other hand, though, radio astronomy facilities use exceedingly sensitive receivers, and so can be disrupted by even a very low level of interfering signal.
While the rulemaking proceeds, the FCC has granted one company a waiver to market equipment in the band, solely for FOD detection at airports, and only under a license.
Comments and reply comments are on a relatively short fuse: 30 and 45 days, respectively, after publication in the Federal Register. We will post the actual due dates when they become available.
This item is admittedly obscure, even by our standards. But we strive to meet the needs of even our most specialized readers.
Since 1996, the FCC has allowed vehicle-mounted radars in the 76-77 GHz band. This band is well up into the “nosebleed” region of the spectrum, approaching the highest frequencies ever authorized. If this band were a sound, only very small dogs would be able to hear it.
The radars up there help to guide the automatic braking systems offered in some high-end cars. They are allowed to emit considerable power – up to 68 watts –when the vehicle is in motion, to achieve adequate range and precision. Greatly reduced power limits apply when the vehicle is stopped, as at a traffic light, in order to protect passing pedestrians from excessive radio-frequency exposure.
A company called Era Systems has asked the FCC for a waiver to allow stationary (non-vehicle) use of radars in this band. Era hopes to install up to ten units on structures at the Atlanta airport. They will be used track the locations of aircraft and vehicles on the ground in ramp and gate areas for “airport management purposes,” possibly a euphemism for keeping things from running into each other.
The requested power is 55 dBm (316 watts), somewhat higher than the maximum for vehicle radars in motion, and much higher than the one-fifth watt limit for stationary vehicles. Era proposes to address the radio-frequency exposure problem by blocking radar emissions towards roads open to the public. Its system uses the same radar modulations as the vehicle units do, and so (according to Era) should not interfere with vehicle radars even if they could see its signals.
The FCC public notice is here; Era’s request is here. Comments are due on May 6, and reply comments on May 18, in docket ET Docket No. 09-55.
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