Weather sentries Machines: Replacing human weather watchers, the Automated Surface Observing System can track the elements just about anywhere, come rain, snow or wandering moose.

February 03, 1997|By Greg Schneider | Greg Schneider,SUN STAFF

From the mountains to the prairies to the Weather Channel in his lobby, Ernest Sessa keeps watch over a vast and unlikely empire.

Sessa designed an automated weather watcher for the Systems Management Inc. subsidiary of AAI Corp.

Now the photos in the conference room look like one of those pranks where bored college students kidnap someone's garden gnome and mail back travelogue photos of it standing in front of various national landmarks.

Here is the Automated Surface Observing System on an Antarctic ice field. An ASOS in the middle of Central Park. One on a platform in Jefferson City, Mo., its spires and whirligigs rising like a Jules Verne island from the flood-swollen Missouri River. Another in Death Valley. Another near Barrow, Alaska.

Almost everywhere Americans have put a good-size airport, AAI Corp. is putting one of its ASOS weather detectors. There will be more than 1,000 out there, eventually. About 850 are already installed.

The company has seven crews constantly on the road, trucking from one site to the next, assembling the little stations.

"They are essentially like bands of Gypsies," said Sessa, 35, chief scientist for SMI.

Sessa drew up the plans for the weather data system in the mid-1980s. SMI beat out a host of competitors, including Magnavox and Lockheed, for a National Weather Service contract that has amounted to more than $200 million.

The government's idea was to replace the traditional manned weather observing stations at 250 airports around the country with a much more vast system of drones.

The drive to automate led to a somewhat arcane controversy over the last few years. Communities that may not have given the subject much thought suddenly turned sentimental upon learning that their local rain-gauge-reading weathercrats were being replaced by machines.

"We find ourselves in really the John Henry scenario. Unfortunately, we're cast in the role of the steel-driving machine, and it's human nature to want to support John Henry," Sessa said.

Baltimore-Washington International Airport showed its human weather watchers the exit last year. AAI is also bidding to put a smaller version of the system, called NEXWOS, at eight general aviation fields around Maryland.

And it has shipped ASOS units to Latvia, Greenland and Saudi Arabia.

By replacing humans, airports get what is billed as a far more efficient system of keeping pilots and air traffic controllers up to speed on the latest weather.

The ASOS takes an observation every minute. Humans did so once an hour. With a combination of lasers, gauges and computers, the ASOS can measure cloud height, wind speed and direction, amount of rain, type of precipitation, visibility, pressure, temperature and more.

All of the measurements zip into airport computers and condense into a 256-character line of symbols. Pilots can dial in and hear the data on their headsets.

The Weather Service, Federal Aviation Administration and the Defense Department have all wanted such a system for many years, Sessa said. But several technological obstacles had to fall first.

For instance, there was never a way for a machine to judge whether it was rain, snow or fog that was limiting visibility, he said. That took human judgment. Now the ASOS uses a sensor in which an infrared beam measures the amount, size and speed of falling particles and, from that, judges whether it's rain or snow.

The system also has to survive all types of hostile conditions. The same machines that sit in 80-below weather in Alaska have to endure the inferno of Death Valley, because the Weather Service wanted spare parts to be interchangeable.

ASOS setups in Alaska are fenced to keep out aggressive moose. Some sensors heat up to discourage bugs, and bristle with spikes to ward off birds.

"You could basically hit it with a cannon shell and it would continue to operate," Sessa said.

Of course, the two-man teams who spend five days assembling the gear aren't nearly so durable. Sessa remembers briefing a bunch of NASA scientists at a site in the swamp outside the Kennedy Space Center. As he spoke, a big cougar slouched out of the woods.

Now Sessa is preparing for what he hopes will be the sale of a big system to the space center later this year, and cougars are on his mind. The folks at Kennedy said what he really needs to worry about are the alligators.

Pub Date: 2/03/97

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