Edwin L. Aguirre
Space is a harsh and dangerous place. Aside from temperature extremes, high vacuum and bombardment of cosmic rays, space travelers also have to worry about extremely high-energy particles – dubbed “killer electrons” – that can pose a hazard to the health of astronauts and shorten the lifespan of orbiting satellites.
“These electrons, traveling at nearly the speed of light, are capable of damaging the satellites’ sensitive electronics and exposing astronauts to high doses of radiation,” says Physics Prof. Paul Song of the university’s Space Science Lab (SSL).
To help understand how these harmful electrons are generated and, consequently, how they can be mitigated, the Air Force Research Laboratory (AFRL) has awarded a three-year contract to a team of UMass Lowell researchers led by Song to support the Air Force’s DSX mission to the Earth’s radiation belts. The DSX’s objective is to explore the role of “wave-particle interaction” in the dynamics of these killer electrons.
The project started more than a decade ago, under the leadership of Prof. Emeritus Bodo Reinisch. The team designed and built a high-power space radio-wave transmitter as part of the DSX’s Wave Particle Interaction Experiment. The transmitter, which is one of the primary instruments aboard the DSX satellite, will send out Very Low Frequency (VLF) transmissions into space using a long dipole antenna that measures 80 meters from tip to tip when deployed.
The DSX satellite was successfully launched on June 25 from Cape Canaveral, Fla., aboard a SpaceX Falcon Heavy, the same rocket booster used by SpaceX CEO Elon Musk to send his Tesla Roadster and Starman mannequin into orbit in February of last year.
During the mission, the researchers will help operate the VLF transmitter and analyze the resulting data at the SSL facility at Wannalancit Business Center on East Campus.
“Our goal is to better understand the wave-particle interaction process,” says Song. “We expect that the transmitted VLF waves will interact with the killer electrons.”
In addition to Song, the other members of the SSL team include Research Prof. Ivan Galkin, who is a UMass Lowell graduate and co-principal investigator for the transmitter project, Research Prof. Jiannan Tu and physics major Brianna Croteau of Lowell, who is an Air Force ROTC cadet at UMass Lowell.
“My role is to participate in the data analysis at the Space Science Lab for my capstone project,” says Croteau. “Being able to do real research and work on a real Air Force space mission, while still being an undergrad and a cadet, is so amazing. It feels great knowing that I am doing real work to help the Air Force. It is a major steppingstone in my future military career, and it is very humbling to work with and learn from the experts on this project. It is an incredible opportunity and I am so happy I could be a part of it.”
How Good Electrons Go Bad
Since the 1960s, scientists have known that during a severe geomagnetic storm, the solar wind – a continuous high-speed stream of charged particles from the sun – impacts and compresses the daytime side of Earth’s magnetosphere, the region around our planet controlled by its magnetic field. Some of these particles become highly energized in the nighttime side of the magnetosphere by processes that are not fully understood. Following a storm, electrons can be energized up to a million electron volts or more, and accelerated up to 94 percent of the speed of light, or more than 280,000 kilometers per second.
The DSX satellite is in an elliptical orbit that will take it to an altitude of 6,000 km at its closest pass, and 12,000 km at its farthest. This will allow the satellite to fly through the inner and outer Van Allen radiation belts that surround Earth while collecting valuable data, according to Song. The DSX mission is expected to last for a year.
UMass Lowell’s role in the DSX mission is built upon the success and engineering capability demonstrated by university researchers in an earlier space mission. SSL scientists designed, built and operated the Radio Plasma Imager for NASA’s IMAGE satellite, which was launched in 2000 and transmitted data for nearly six years before ground controllers suddenly lost contact with it in 2005. Last year, NASA was able to re-establish radio contact with IMAGE, albeit very weakly.
UMass Lowell received more than $12 million from NASA to build the Radio Plasma Imager, and it paved the way for many more research grants that followed.
“Thanks to data gathered by RPI, four Ph.D. theses were completed at UMass Lowell, and more than 60 papers in refereed journals have been published worldwide,” notes Song.