David Hysell’s eye on the sky may point the way to improved satellite communications.

Attempts to unlock the mysteries of the heavens have taken David Hysell to exotic locales the world over, enabling the Cornell scientist to test his equipment and theories, sometimes in places you’ll never hear of at your local travel agency. The journeys never get old for Hysell, an associate professor of Earth and Atmospheric Sciences who just keeps racking up the frequent-flyer miles and mountains of data.

An expert on plasma waves in the earth’s ionosphere, the globetrotting Hysell has done time at Cornell’s radar observatories at Arecibo, Puerto Rico, and Jicamarca, Peru, as well as lugging a portable radar system of his own design to places such as St. Croix, Virgin Islands, and Anchorage, Alaska.

In August Hysell set up shop on Kwajalein Atoll in the Marshall Islands, a chain of coral specks in the Pacific Ocean between Japan and Hawaii. The remote site doesn’t offer much in the way of beachfront resorts, but through an agreement between the U.S. and Micronesia, it does have sophisticated, high-powered radar installations ideal for military and scientific experimentation.

Which is why NASA will, on occasion, take its sounding rocket program to the atoll and offer access to the facility to researchers who have projects with promising applications for the public and private sectors. Among the projects that have been tested in the Marshall Islands region is the much-hyped strategic defense initiative (SDI), also known as the Reagan “Star Wars” plan.

Hysell’s experiments in the ionosphere may lack the high-profile publicity of SDI, but they did catch the eye of NASA when it came time to parcel out research grants for outside access to the government installation on Kwajalein for projects requiring both rockets and radars.

The project was one of four selected from a dozen proposals submitted to NASA, as was another experiment designed to analyze the neutral winds associated with ionospheric gravity wave disturbances offered by Lynette Gelinas of Cornell’s Laboratory of Plasma Studies. All participants have to design and assemble a payload with their own scientific instrumentation, while NASA provides Army or Navy booster rockets to deliver the goods.

Hysell notes that Cornell has a long history of studying the ionosphere, including research conducted at the Arecibo facility. He has been a part of that history, earning a Ph.D. in electrical and computer engineering from Cornell in 1992. “Now I am continuing that work in EAS.”

The ALTAIR radar collect data to identify the conditions for launch and place the rocket measurements in context.

Before returning to Cornell in January 2002, Hysell was a physics professor at Clemson University in South Carolina and a post-doctoral researcher with Cornell’s Space Plasma Physics Group, doing joint research in Russia and Ukraine.

Hysell’s most recent project focused on the equatorial ionosphere, the outer edge of the atmosphere comprising fluctuating layers of ionized atoms and molecules. “We study this for a number of reasons,” he says. “It’s part of the geophysical environment, and we need to understand it in order to understand how spacecraft operate, or how radio waves operate.”

In particular, Hysell was investigating the phenomenon of “spread F,” or instability in certain layers of the ionosphere in equatorial regions, and gathering data on the density, temperature, composition, and dynamics of the upper atmosphere. “At low altitudes the ionosphere is unstable, just like the atmosphere can be unstable and create hurricanes and tornadoes,” he said.

“F” refers to a specific region of the ionosphere; “spread” refers to the signatures picked up on the radio receiver using radio wave propagation that are visually spread, indicating a disturbance. Hysell’s research seeks to determine the conditions or factors that trigger this phenomenon.

The Terrier Orion, a two-stage rocket system, is elevated prior to launch.

An ionosphere with a smooth electron density gradient presents few problems for satellite communications, but strong density irregularities, measuring hundreds of meters, will have an adverse impact on the propagation of electromagnetic waves that are the basis for such communications.

At the same time, the ionospheric irregularities that can interfere with radio communications can also serve as targets for high-powered ground-based radars, which scatter off plasma waves with wavelengths equal to half the radar wavelength. This provides investigators with a means of studying ionospheric parameters from the ground using remote sensing. Observing programs that utilize this phenomenon have been carried out regularly at Arecibo, Jicamarca, and elsewhere for about 40 years. NASA sounding rocket campaigns are scheduled periodically to make pinpoint measurements of ionospheric parameters with a level of detail inaccessible to ground-based radars.

Complicating matters is the fact that spread F is not confined immediately to the ionospheric regions where it is most easily detected but actually maps along Earth’s magnetic field lines to off-equatorial latitudes and to lower altitudes in the ionosphere. A substantial fraction of Earth’s population therefore resides under regions susceptible to spread F.

This spread F condition typically occurs at sunset, when the layers of the ionosphere reorganize so that the lower section of the ionosphere becomes steeper, Hysell explains. Instability follows, as materials of different density mix, much like a combination of oil and water, and the radio waves break up.

This instability in turn produces a display of plasma waves ranging in size from a few centimeters to a thousand kilometers. “It’s a very turbulent environment, and if you try to propagate radio waves through it, you will have problems,” says Hysell. Those issues include disruptions in satellite communications, such as common GPS (global positioning system) satellite navigation, aircraft landing, and missile targeting systems.

“With this type of diffraction screen, ground-to-satellite or ground-to-ground communications would be distorted,” Hysell says. “Communications among computers would be so distorted that the information would be unintelligible.”

Hasan Bahcivan, a graduate student in electrical and computer engineering who collaborated with Hysell on the spread F experiments, adds that while the immediate application of spread F research is to predict disruption of communication and navigation signals, “The main purpose of this campaign was more science, to study the triggering mechanisms of spread F.”

Knowing where and when spread F will occur, then, would be a boon to military officials fixing targets and guiding missiles, providers of satellite-based TV or radio, oil drillers using satellite guidance to locate their platforms, or nautical navigators using GPS to fix their positions in the middle of the ocean.

“Much is known about these instabilities, but what is not known is how you forecast or predict the erratic behavior,” Hysell explains. “People want to know on a given night if spread F is occurring, so we need to create a model for predicting the instability.”

To create that model, Hysell probed the ionosphere with rockets carrying instruments designed to identify and analyze its plasma density, temperature, collision frequency, and electric field profiles. Researchers from Clemson University, Utah State University, and Penn State University served as co-investigators, supplying rocket payload hardware and collaborating on data crunching duties.

The experiment was run twice, once on the night of August 7 and again on August 15. Each involved the launch of three 40-foot rockets; two carried a powdered aluminum (trimethyl aluminum or TMA) release payload that dusted the target layers of the ionosphere, highlighting the atmosphere like the glow of the northern lights, while the third contained instruments to collect data from the targeted region.

The unguided missiles contained instruments, telemetry technology to transmit data to the ground, and altitude control to keep them properly oriented. “It was basically point and shoot, and trust that they would arrive where they were supposed to,” says Hysell.

When the payload was deployed, booms extended from the projectile with instruments to measure electric fields. From blastoff to splashdown, the entire experiment takes about 10 minutes.

Another critical component was the Department of Defense’s high-powered ALTAIR radar, typically used to track government missiles and satellites, but also useful in scientific endeavors.

Photos of the ionosphere and wind measurements at altitudes ranging between 80 and 220 kilometers above Earth were taken after the chemical release, in an effort to determine if the winds at these heights are responsible for influencing the ionosphere in a way that scientists have not yet determined. Three chemical trails were created for measurements of wind flow profiles at three locations.

“We are evaluating the stability of the ionosphere at a given time and place,” says Hysell. “This [spread F] phenomenon is most readily detected at low and middle latitudes, where the magnetic field is close to being horizontal. It so happens that where we were it is a summer phenomenon, and everywhere in the world it is a post-sunset phenomenon.”

The research was not without a few tense moments. “We had a window of only two weeks, with experiments at the atoll scheduled right before and right after ours,” Hysell says. “Night after night we waited for spread F to occur and for clear skies. I think the NASA people were more anxious than anyone else because they wanted to see the experiments completed.”

Launch of the first Terrier Orion. The vehicle carried a payload that deployed a chemiluminescent trail photographed and tracked from the ground.

The four-hour countdown to launch was faithfully carried out each evening after dark, in hopes of favorable conditions. Finally after five days, conditions were right for the first launch, followed by a second eight days later.

With the experiments completed, Hysell and his students now face the task of evaluating the information obtained through the rocket launches and preparing models for predicting the occurrence of spread F. His hypothesis is that shear flow, or the change in the speed and direction of wind flow in relation to altitude, is a precondition for spread F.

“In the F region of the ionosphere the flow is violently sheared; at lower altitudes the flow is westward, and at higher levels it is eastward,” Hysell explains. “We need to understand why that is, to measure every conceivable shear flow parameter and put that into our computational models for spread F.”

Analyzing the data will take years, but the Cornell researcher is undaunted. “This a great field to work in. We build our own instruments, write the code for delivering the rockets and processing the information, and deploy them in some extraordinary locations,” he says.

The research is compelling, too, because all of the components — from analyzing fluid dynamics to designing and fashioning custom hardware to writing code — involve both student and teacher.

For grad student Bahcivan, enrolled in courses on upper atmospheric and ionospheric physics, the spread F project provides a wealth of information to complement what’s being taught in class. “The experimental and theoretical nature of the ionospheric research is something I would like to be involved with in a future career,” he says. “I believe there is a lot of plasma physics to learn here, and the good part is you can see it for yourself with experiments involving radars or rockets.”

“And it has practical consequences,” Hysell says. “We can take the mystery out of the ionosphere and, hopefully, make the world safer by improving vital communications.”

Jay Wrolstad is a freelance writer in Ithaca.