If you're easily startled by big, low-flying airplanes, you'll need to get a good grip on the steering wheel Monday.
NASA will be starting a monthlong campaign of air pollution sampling, using a four-engine turboprop P-3B Orion to skim 1,000 feet over Central Maryland's interstate highways to gather air samples.
A thousand feet is about the height of the TV towers on Television Hill in Baltimore, or twice the height of the Washington Monument in the nation's capital.
Public safety officials have been told to expect anxious phone calls next week as the flights get under way. The aircraft will fly a circuit from Beltsville and Annapolis to Cecil County and back, sometimes flying low along Interstate 95, the Baltimore-Washington Parkway and the Baltimore Beltway.
"It's something that's going to be very obvious to people," said Kenneth E. Pickering, project scientist for the mission, called Discover-AQ. "My hope is that the majority of people will have heard of us."
"NASA has done extensive notification of all the authorities, from Homeland Security to the Federal Aviation Administration, to the state police and so on," he said. So, residents who were not already aware of the campaign can call and get a reassuring explanation.
Next week's flights will be tests, with science flights starting July 1. The aircraft will fly on 12 to 14 days in July, starting as early as 6 a.m. and ending as late as 8 p.m. Cloudy days could ground flights.
Planning has been under way for a year. The mission is part of a project involving NASA, the Maryland Department of the Environment, the Environmental Protection Agency and several universities.
NASA satellites already provide data useful in air quality measurements, Pickering said.
"But there's limitations to what you can get from satellites about what the air is like down here at the surface where humans are breathing," he said. "We need data to help us with the interpretation of satellite data, to better represent what's going on near the surface."
The flight data will aid in the design of the next generation of air-monitoring satellites. Unlike the current satellites, which fly polar orbits and pass over Maryland once a day, the next generation will be placed in geosynchronous orbits, capable of providing data in near-real time.
Another goal is to determine the optimal design for a network of surface monitoring stations for the region, said James Crawford, the project's principal investigator, at the NASA Langley Research Center in Hampton, Va.
"If we had to put resources on the ground, can we define the minimum suite that makes satellite observations interpretable?" he said.
At the state level, "we'll be looking for improvements in the satellite products that help us make better air quality forecasts and better understand the interstate transport of air pollutants," said Dave Krask, program manager for the Maryland Department of the Environment's Ambient Air Monitoring Program.
The flight data could also help "better identify air pollution hot spots and the conditions and sources that contribute to them," Krask said.
The import of pollutants from the west, chiefly from coal-burning power plants in the Ohio Valley, has been a nagging environmental problem for Maryland.
State efforts to reduce the number of "unhealthy" air pollution days in Maryland have shown some success, Krask said, with fewer days exceeding federal pollution limits relative to the number of 90-degree days, when unhealthy air is most likely.
But previous studies using aircraft and balloons have shown that on some of the state's worst air quality days, the air high above the ground, drifting from other regions, is already badly polluted. On those days, Krask said, "it doesn't take much in terms of local emissions to push us over the limits."
The NASA campaign is expected to improve understanding of out-of-state sources of Maryland's air pollution and how it moves and evolves as it crosses the state. NASA will be flying two aircraft during the campaign.
The low-level P-3B Orion based at the NASA Wallops Flight Facility near Chincoteague, Va., will fly a circuit over Central Maryland. It will descend to 1,000 feet over Beltsville, recording how pollution levels change with altitude. From there, it will fly at 1,000 feet to Padonia in Baltimore County, then climb to as high as 15,000 feet and cross to Fair Hill in northeastern Cecil County. There, it will spiral down to 1,000 feet, then fly southwest. It will make one low-level pass over I-95 in Cecil and Harford counties, and another between Edgewood in Harford and Essex in Baltimore County. From Essex, the P-3B will head over the Chesapeake Bay, passing over the Bay Bridge, and back to Annapolis, then west to Beltsville to repeat the circuit.
"It's a busy airspace," Pickering said. "We've had several meetings with the FAA to get their approvals for it, so that's all been worked out. They've approved it."
The P-3B will carry more than a dozen scientists who will operate equipment designed to measure atmospheric levels of ozone, nitrogen dioxide, formaldehyde, particulates, nitric oxide, carbon monoxide, carbon dioxide, methane and hydrocarbons.
A smaller aircraft, a twin-engine King Air out of NASA Langley, will fly along the same path, but at a constant 26,000 feet. It will measure the air column beneath it for concentrations of ozone, nitrogen oxide and formaldehyde.
To supplement the airborne campaign, the Maryland Department of the Environment will take simultaneous data from six of its air-monitoring sites in the region. NASA will add its sensors at the same ground sites and at Fair Hill.
In Edgewood, a team from Pennsylvania State University will launch air sampling balloons, and another group from Millersville University in Pennsylvania will loft tethered balloons to measure pollutants.
Howard University will staff instruments on its property in Beltsville and will loft free and tethered instrument balloons there with a Penn State team.
The Baltimore-Washington area was chosen in part because of its proximity to Langley and the NASA-Goddard Space Flight Center in Greenbelt, where Pickering is based.
"We thought we'd go with something local to start with, Pickering said.
More importantly, while the region's air is "not the worst in the country," he said, "it is an area in nonattainment of the [federal air-quality] standards."
Future campaigns are being considered during the next five years for Houston and other urban areas still to be determined.
As the mission gets under way, a NASA website will provide near-real-time updates on the airplanes' locations and flight plans: http://www.nasa.gov/discover-aq
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