But even the Perseus has its limitations. "Flights will have to be pretty short -- about one hour at 80,000 feet [24 kilometers]," Langford says. "Perseus will only be able to carry a single instrument, while Thesarus will be able to carry up to 700 pounds of payload."
Perseus is now in the testing and flight stage. Aurora is currently working with a five million dollar grant from NASA.
The Future
With the ability to go to even greater altitudes than the ER-2 does, Wennberg and Anderson are anxious to gain a more complete understanding of the chemistry of ozone depletion.
"There are essentially two issues [in determining ozone depletion]: the rapid change of aerosol loading, dictating the amount of surface area that is exposed, and the change in ultraviolet radiation," Anderson says. Regional and seasonal variations can lead to vast differences in ozone levels, he adds. "The polar regions are almost different planets."
"There is a three-week period over the Antarctic with massive destruction due to high chlorine, some time and a lot of sunlight," Anderson says. "The preparation is the same over the Arctic, but there isn't enough sun to generate the ozone hole like that over the Antarctic."
Recent NASA measurements from Russian satellites indicate that the Antarctic ozone hole is maintaining a size roughly the same as the North American land mass.
Salawitch cautions that even with the current data, there are still a lot of uncertainties.
"The results are uncertain because lot of key reaction rates have not been measured at low temperature in the lower ozone layer," Salawitch says. "We also really don't have an accurate understanding of how engine exhaust is transported to higher altitudes."
And Wennberg notes that the mechanism by which aircraft exhaust is diffused has yet to be explained. "If 10 percent of the exhaust is transported upwards in the atmosphere and 90 percent down, the net ozone loss would be zero," Wennberg says.
Anderson says that this area is very active in the research community. "The indication from tracers is that the atmosphere mixed horizontally and vertically," he notes.
And Anderson's group is already moving to understand more of the related chemistry.
Recently, the ER-2 flew through the exhaust of the Concorde off Christchurch, New Zealand at an altitude of 53,000 feet. Anderson's group is currently analyzing the data.
"Right now, we only have models to predict what we will find above 22 kilometers," Wennberg says. "In situ data will be much more precise and unparalleled."
"With the Perseus-like technology, we will be able to look in good detail" to understand the chemistry of the ozone layer, Wennberg says. "We are measuring levels that are 1 part in a trillion, and then changes that are 0.01 of 0.001 parts per trillion."
It is unlikely such measurements will be possible from remote payloads such as those on satellites or the Space Shuttle, Wennberg says.
Despite the technological difficulties Wennberg and Anderson have encountered, atmospheric researchers are continuing their efforts to understand all areas of the ozone layer. And scientists involved with their research are optimistic about future efforts.
"The paper is another step along the road [to understanding the chemistry of the ozone layer]," says David W. Fahey, a research physicist at the National Oceanic and Atmospheric Administration Aeronomy Laboratory, and co-author of the paper. "The stage has been nicely set."