AR12: Continuing to explore
Main Page Content
When NASA holds a press conference to officially rename one of its space missions, there must be a compelling reason.
And on Oct. 9, 2012, when a two-satellite mission to explore the Van Allen radiation belts was renamed as the “Van Allen Probes” mission, NASA gave the reason in a press release:
“James Van Allen was a true pioneer in astrophysics,” says John Grunsfeld, astronaut and associate administrator for NASA's Science Mission Directorate at the agency’s headquarters in Washington, D.C. “His groundbreaking research paved the way for current and future space exploration. These spacecraft now not only honor his iconic name but his mark on science.”
As the NASA release further noted, the work of Van Allen and the University of Iowa go all the way back to the beginning of the Space Age.
What NASA might also have said is that the UI’s proud history of space exploration continues to the present day, with the UI having been a part of 65 space exploration missions, including the current Van Allen Probes mission.
The very names of the satellites and spacecraft stimulate the imagination. They include: Explorer, Pioneer Injun, Discoverer, Mariner, Hawkeye, Helios, Voyager, International Sun-Earth Explorer, Firewheel, Plasma Diagnostics Package, Galileo, Geotail, Wind, Polar, Cluster, Mars Express, and Juno.
The foremost highlight of UI space exploration remains Van Allen’s landmark discovery of the radiation belts, two concentric, doughnut-shaped bands of intense radiation encircling the Earth, took place in 1958 with instruments he and his UI colleagues designed and built. The instruments were carried aboard Explorer 1, the first successful U.S. satellite.
Today we know that the belts are affected by solar storms and coronal mass ejections and sometimes swell dramatically. When this occurs, they can endanger communications, GPS satellites, and human spaceflight activities.
Van Allen went on to serve as the principal investigator for scientific investigations on 24 Earth satellites and planetary missions. His research highlights included his 1973 first-ever survey of the radiation belts of Jupiter using the Pioneer 10 spacecraft and the 1979 discovery and survey of Saturn’s radiation belts using data from the Pioneer 11 spacecraft.
In recognition of his work, he received many awards including a NASA lifetime achievement award, membership in the National Academy of Sciences, the National Medal of Science presented by President Ronald Reagan, and the Crafoord Prize—for space exploration, the equivalent of the Nobel Prize—from the Royal Swedish Academy of Sciences.
Another highlight of the UI’s history in space began with the launch of NASA’s Voyager 1 spacecraft in 1977. The craft carries a host of instruments, including those of UI space physicist Donald Gurnett, principal investigator for Voyager 1’s plasma wave instrument.
Gurnett used data from UI-built Voyager instruments to make the first observations of plasma waves and low-frequency radio emissions in the magnetospheres of Jupiter, Saturn, Uranus, and Neptune and discovered lightning in the atmospheres of Jupiter and Neptune.
In recognition of these and other discoveries, Gurnett, a James A. Van Allen-Roy J. and Lucille A. Carver Professor, has received numerous honors, including election to the National Academy of Sciences. In 2004, he was elected a Fellow of the American Academy of Arts and Sciences (AAAS) for bringing science into the public and private sectors. His collection of more than 40 years of space sounds served as the inspiration for Sun Rings, a multimedia piece composed by Terry Riley and performed by the Kronos Quartet to international acclaim.
Fittingly, he began his career by working on spacecraft electronics design as a student employee in the UI physics department in 1958 and received his doctorate, under the direction of Van Allen, in 1965.
Despite the many planetary discoveries made using Voyager 1, the spacecraft’s main claim to fame may be linked to its longevity. In other words, it is on track to become the first manmade object to leave the solar system and enter interstellar space.
In September 2012, Voyager 1 celebrated its 35th birthday as the most distant manmade object at more than 11.3 billion miles from the sun or about 122 astronomical units (AU)—one AU is the distance between the sun and Earth—and is approaching the heliopause, the region where the gaseous influence of the sun ends and interstellar space begins.
As Gurnett noted during a special NASA panel presentation, it takes more than 16 hours for a radio signal to travel from the spacecraft to one of NASA’s Deep Space Network antennas. The signal strength is so incredibly weak that it requires a giant 230-foot-diameter dish antenna to pick up the signal.
A third highlight of the UI’s history of space exploration may turn out to be the Van Allen Probes mission, in spite of the fact that the mission’s twin, Earth-orbiting satellites were just launched in August 2012. Although the mission has only just begun to collect data, it holds the promise of building upon the UI’s solid foundation of radiation belt exploration.
Renaming the mission makes good scientific and historic sense, says Craig Kletzing, the UI’s F. Wendell Miller Professor of Physics and Astronomy and principal investigator for one of the five instrument suites on NASA’s Van Allen Probes mission.
“Professor Van Allen discovered the radiation belts at the beginning of the Space Age over 50 years ago. Today, there remains much to learn about how they work, how the sun delivers energy to the environment about the Earth, and how the interaction between the sun and the Earth creates these two bands of very energetic particles called the Van Allen radiation belts,” he says.
The instrument went on to capture data that at first puzzled UI researchers because it seemed as though the instrument was giving false readings. Only when they realized that the amount of radiation was so intense that it literally overwhelmed the Geiger counter aboard the satellite did they realize that they had discovered an area of high intensity radiation, phenomena later called the Van Allen radiation belt.
And as Kletzing said in an October 2012 appearance on National Public Radio’s Science Friday program: “What Van Allen and others expected to see were just cosmic rays of fairly low-level intensity as the satellite orbited the Earth.
“What they found instead was that the count rate started to climb and then it went to zero. They scratched their heads for a while. Finally they realized there was so much radiation there that it was saturating the detector—it just couldn’t count anymore—it was overwhelmed.”
As Van Allen himself commented after discovering the radiation belts: “They told us our instrument had stopped working. We knew better and realized we had encountered a whole new phenomenon in space.”