Making Measurements That Count

Helen Worden and family on a boat JPL's Helen Worden enjoys time away from the lab with her family.
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April 01, 2005

A bag of groceries isn't a meal, and a pile of bricks isn't a house. It takes skill to turn raw materials into finished products. And how well they turn out depends both on the quality of the ingredients and how they are handled.

JPL's Dr. Helen Worden helps turn raw satellite observations into measurements that tell us more about some important gases in the air we breathe than we have known before.

Worden is algorithm team leader for the Tropospheric Emission Spectrometer, an instrument launched into space in July 2004 onboard NASA's Aura satellite. The instrument measures ozone and other gases in the lowest layer of the atmosphere, the troposphere, which extends from Earth's surface up to about 12 kilometers (7 miles).

Making those measurements isn't simple. "Understanding the data that comes from the instrument requires a lot of processing," says Worden. "We have to convert raw data into something we understand about the atmosphere, for example, how much pollution there is. To do that we use algorithms."

She explains, "Algorithms are sets of equations that change one set of numbers into another. For example, the computer in a modern car reads several sensors and applies algorithms to calculate spark timing and fuel injection for optimal efficiency and lower emissions."

Applying different algorithms allows scientists to extract the particular kind of information they're looking for. "Some people may be interested not just in ozone but in the infrared radiance of the atmosphere," says Worden. "We develop different algorithms to create different data products and to get as much useful information from the data as possible."

Developing these algorithms is the job of the 22-member science team, and Worden's responsibility is to coordinate those efforts. Ongoing calibration and validation activities make sure that the final results, the data products from the instrument, are correct and reliable.

"The best part of my job is figuring out the data," says Worden. "It's like solving a puzzle. It's something that didn't make sense when you first looked at it and then you figure it out. It's also the worst part of my job -- not understanding the data," she adds, "that and the meetings."

Though the Tropospheric Emission Spectrometer launched less than a year ago, Worden and her colleagues had lots of advance practice fine-tuning the instrument and figuring out how to interpret its data. An airborne version of the instrument flew several missions providing measurements similar to those they now get from space. A high point for Worden was a trip with the airborne instrument around the Pacific Rim, flying over Hawaii, New Zealand and Australia. "It was a thrill," she says. "We took some really interesting data over forest fires and volcanoes."

"As much preparation as you do, however, " says Worden, "you can never account for everything you see on orbit. But we understood a lot about the instrument before launch, which has meant fewer snags. We have been able to measure ozone in the lowest level of the atmosphere. That was our main goal. Before we only knew the total average amount. Now we have vertical information on a global scale, something we've never had before. This will make big improvements to models of atmospheric chemistry."

"We hope the instrument has a good long life and we can keep improving our measurements," says Worden.

Working on the Tropospheric Emission Spectrometer is something of a family affair for Worden, who has been at JPL now for 12 years. Her brother, John, is also a member of the science team, and he works on algorithms as well. "I was here first," Worden is quick to point out. "Actually, having him here isn't as weird as I thought it might be."

Worden comes from a family of scientists and engineers. Her father was a physicist. Her older sister has a Ph.D. in engineering and works for Ball Aerospace. She met her husband, now a radar analyst engineer at Raytheon, at Cornell University where they both received their Ph.D.s in high-energy physics.

Originally from Seattle, Washington, Worden lived in several different places while her parents' work in rural community development took them to Venezuela and Chile, among other assignments. "I can remember when I was really young being more interested in art," says Worden, "and I loved to draw, like my daughter. But I really started enjoying math in school."

For more information about the Tropospheric Emission Spectrometer, visit their site at

Media contact: Alan Buis (818) 354-0474
NASA's Jet Propulsion Laboratory

Written by Rosemary Sullivant


Helen Worden and team in front of a plane

Worden, third from right, with the team who took the Tropospheric Emission Spectrometer on a flight around the Pacific Rim.

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